PG Thesis

Permanent URI for this collectionhttp://localhost:4000/handle/123456789/2

Browse

Subject: search.filters.subject.Plant Breeding and Genetics

Search Results

Now showing 1 - 10 of 82
  • No Thumbnail Available
    Item
    Screening for drought tolerance in cocoa hybrids (Theobroma cacao L.) and expression analysis of identified gene
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellanikkara, 2025) Santhra Mohanan.; Minimol, J S
    Cocoa (Theobroma cacao L.) is a high-value, export-oriented beverage crop, empowering small-scale farmers through global value chain participation. Originating from the humid rainforests of South America, cocoa requires annual rainfall between 1500–3000 mm, and summer irrigation of about 24 liters per plant every four days. However, climate change-induced rainfall unpredictability, particularly in non-traditional cocoa growing regions of India like Tamil Nadu, Andhra Pradesh, and North Eastern states, severely limits water availability, increasing the vulnerability of crop to drought. Shallow root system further exacerbates its sensitivity to water stress, restricting its ability to access deeper soil moisture and significantly affecting yield and supply. Despite the identification of drought resistant genotypes in controlled conditions, their field level efficacy remains largely unexplored. Plants exhibit complex morpho-physiological and biochemical mechanisms in response to drought, notably through signaling molecules such as reactive oxygen species (ROS) and osmolytes that mediate stress responses. However, translating these findings into field resilience in cocoa remains a major challenge. This study aims to identify drought resistant cocoa hybrids under field conditions by evaluating key biophysiological parameters along with gene expression analysis, thereby contributing to the sustainable enhancement of cocoa production amidst growing climate variability. Twenty cocoa hybrids planted during 2018 at Cocoa Research Centre, which are at yielding stage served as the base population for the present study. Morphological characterization based on qualitative and quantitative characters were carried out. Thirteen pod characters and ten bean characters were studied among the hybrids, of which all the characters except for number of furrows and ridges showed high variability. The hybrids were evaluated for the biochemical properties with a focus on determining fat and total polyphenol content of beans. A significant difference in biochemical characters was observed among the hybrids with the highest fat and polyphenol content recorded in H102 (55 %) and H103 (8.56 %), respectively. Correlation study between the weight of beans per pod and other quantitative traits showed a significant positive association with pod weight, total beans, single bean dry and fresh weight, bean length, and width. Path analysis further indicated that five of these traits exerted a direct positive influence on bean weight per pod, whereas the contribution of bean length was minimal, with a negligible path coefficient value of 0.063. Based on scoring and ranking in terms of yield parameters, H101 and H153 were selected as top performing hybrids. Field screening for drought resistance was conducted on these twenty hybrids by initially flood irrigating until the relative water content reached 80 per cent, followed by drought induction through the suspension of irrigation until the onset of incipient wilting symptoms, and subsequently alleviating the stress by reapplying flood irrigation. Based on the days taken to wilt, hybrids were classified using the score chart. Hybrids exhibited differential responses to drought resistance screening. H152, H153, H101, and H102 were found to be highly resistant where as H141, H169, and H103 exhibited moderate resistance towards drought. Highly resistant hybrids retained relatively high values for physio-biochemical parameters under drought stress than the susceptible ones. Correlation studies between days taken to wilt and physio-biochemical parameters revealed significant positive associations with all parameters except transpiration rate (r = -0.652**) and stomatal conductance (r = -0.524*). According to path analysis, eight variables including Relative Water Content (RWC), chlorophyll content, catalase, membrane stability, glycine betaine, proline, transpiration rate, and stomatal conductance exerted a direct effect on days taken to wilt, with RWC exhibiting a very high positive direct effect (1.33). Principal component analysis delineated three components (PC1, PC2, and PC3) with eigen values exceeding the Kaiser criterion threshold (>1), accounting for 75.78 per cent of total variation, with PC1 contributing maximum variability (56.94 %). RWC and superoxide dismutase exhibited maximum contribution to PC1 with a strong positive correlation of 0.901 and 0.890, respectively with PC1. Scoring and ranking of hybrids based on significant physio-biochemical characters regarded H103 and H169 as drought resistant. According to the prior transcriptomic study, laccases (LACs) were found to be upregulated in drought tolerant genotypes and were selected for the present gene expression profiling. The expression study was undertaken at different soil moisture regimes (100% and 40%), using two contrasting hybrids identified as drought resistant (H103, H169) and susceptible (H8, H55). H103 exhibited a pronounced upregulation with a 9.81-fold increase of the targeted gene under 40 per cent field capacity (FC) relative to its 100 per cent FC. In contrast, the susceptible hybrid (H65) manifested a comparatively attenuated response, with only a 1.89-fold increase, indicating a limited capacity for stress-inducible gene activation. Although H103 and H169 exhibit strong drought resistance, their yield performance under ambient conditions remains suboptimal. Hence, H101 and H141 were identified as top-performing hybrids due to their excellent yield and strong drought resistance.
  • No Thumbnail Available
    Item
    Screening early segregating generation of brinjal (Solanum melongena L.) for resistance against shoot and fruit borer
    (Department of Plant Breeding and Genetics, College of Agriculture Vellanikkara, 2024-01-31) Ankit Kumar Upadhyay; Jiji Joseph
    Brinjal, known as eggplant or guinea squash (Solanum melongena L.), belongs to the Solanaceae family. The fruit from the genus Solanum is also called “The King of vegetables”. It is an important solanaceous crop cultivated worldwide and is native to the Hindustan-China center, where it still grows in the wild. The brinjal crop is highly vulnerable to several pests and diseases. Among these, the production and productivity of the crop are severely affected by brinjal shoot and fruit borer (BSFB; Leucinodes orbonalis G.) reducing its market value. The loss caused by the pest may reach up to 70 - 92 per cent. The inadequacy of reliable biological control for the management of BSFB leaves farmers to resort to insecticides. This underscores the critical necessity for extensive research and the development of varieties resistant to shoot and fruit borer. Such resistant varieties have the potential to emerge as the most environment friendly, cost-effective, and sustainable method for pest control. In this context, the present study entitled “Screening early segregating generations of brinjal (Solanum melongena L.) for resistance against shoot and fruit borer” was conducted to investigate and select the superior lines with resistance to shoot and fruit borer from early segregating generations. Segregating generations of two crosses i.e., Ponni × Vengeri (F3 and F4 generations) and Ponni × IC624241 (F2 generation) were evaluated along with the parents and check varieties. Segregation with wide variation was observed in all the generations viz—F2, F3, and F4 of the respective crosses. Regarding fruit colour, both the segregating generations of Ponni (green) × Vengeri (purple-green) showed wide variation in the colouring pattern. The segregating generations had both oblong and long-shaped fruits similar to parental types i.e., Ponni (oblong) and Vengeri (long). Besides, elongated fruits were also observed in both generations. All the fruits in the F2 generation of Ponni × IC624241, exhibited green colour similar to the parent Ponni whereas, the fruit shape was round as in IC624241. Range, mean, variance, genotypic coefficient of variance (GCV) (%), phenotypic coefficient of variance (PCV) (%), heritability (H2), genetic advance (GA), genetic advance as percentage over mean (%) (GAM), skewness, kurtosis, and correlation between growth and yield traits were estimated in F2, F3, and F4 75 generations of the respective crosses. PCV was higher than GCV for all the traits in all the generations. The observed variability across all studied populations remained consistently high for various traits. This variability persisted in the subsequent generations, as indicated by the range, GCV, PCV, H2, GA, GAM, skewness, and kurtosis. This suggests that a single seed descent (SSD) method was employed throughout the generations without any selection process. For pedigree selection BSFB scoring according to Mishra et al., (1988) at the fruiting and shooting stage was performed and all the lines were categorized as susceptible to highly susceptible in accordance with their scale. The selection criteria for identifying the best-performing lines were based on percentage of fruit infestation, marketable yield, fruit yield per plant, and percentage of shoot infestation. Based on the selection criteria lines 1.2.18, 1.2.10, and 1.3.10 were identified from the F3 generation of the cross between Ponni × Vengeri and were forwarded as F4 lines. In the F2 generation of the cross between Ponni × IC624241, five F2 plants showed 50 per cent of fruit resistance but, due to susceptibility to bacterial wilt and low population size, further studies were not conducted. Correlation data from F3 (Ponni × Vengeri) and F2 (Ponni × IC624241) generation of the crosses revealed a positive association between the number of flowers, number of shoots, fruits per plant, and length of fruit with shoot and fruit infestation. However, in the F4 generation of Ponni × Vengeri the length and diameter of the fruit showed a negative correlation with the shoot and fruit infestation by BSFB. Fruit yield per plant was positively associated with the number of flowers, shoots, fruits, length of fruit, and average fruit weight in all the studied populations. The diameter of the fruit also showed a positive association with yield in the F2 (Ponni × IC624241) and F4 (Ponni × Vengeri) populations of the crosses. Superior lines selected through the pedigree method in terms of marketable yield and resistance to BSFB were identified from the F3 forwarded F4 generation of Ponni × Vengeri, the lines were 1.2.18.8, 1.2.10.7, and 1.3.10.7 (in descending order of their performance). The superior lines with resistance for fruit infestation from F4 generation developed through SSD were 1.3.11.2 (0 %), 1.4.13.2 (50 %), and 1.10.16.4 (0 %). The identified lines from the F4 generation of cross Ponni × Vengeri may be forwarded further to develop resistant varieties and other studies.
  • No Thumbnail Available
    Item
    Identification of yellow mite resistant lines in early segregating generation of chilli (Capsicum annuum L.)
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellanikkara, 2025-03-14) Mithun Vasudev; Asish, I Edakkalathur
    Chilli (Capsicum annuum L.), is one of the most important vegetables as well as spice grown in tropical and subtropical regions. However, the productivity of chilli is adversely affected by insect complex especially aphids, thrips and mites. Chemical management of mites are often not encouraged due to negative consequences such as residue in harvested produce, pesticide resistance and various other environmental problems. Development of resistant varieties that utilize plant defence mechanisms is the sustainable solution. In this context, the present study entitled Identification of yellow mite resistant lines in early segregating generations of chilli was carried out during 2024. Previous study conducted at the Department of Plant Breeding and Genetics, Vellanikkara had identified three moderately mite resistant chilli hybrids viz., Anugraha x 417, Anugraha x 445, and 451 x 445. F2 and F3 generations of above three crosses along with their parents served as the experimental material for the present study. Varieties viz., Anugraha and Ujwala were used as checks. F2 generation of the above three hybrids each with a population size of 200 plants were raised for evaluation. Hundred plants belonging to F2 generation of each cross were raised in the open field condition and the remaining 100 plants under the polyhouse. Parents involved in the above crosses were similar in qualitative characters such as hypocotyl colour, cotyledonous leaf colour, stem colour, nodal anthocyanin, leaf colour, leaf shape, flower position, corolla colour, anther lobe colour, filament colour, stigma exertion, calyx pigmentation, anthocyanin spots on fruits, fruit colour at intermediate stage, fruit shape, mature fruit colour, fruit blossom end appendage, fruit cross-section corrugation, fruit surface, seed colour and seed surface. So, there was no variation for these traits in the F2 generation. Corolla shape and fruit shape at the blossom end segregated in 9:7 ratio in the F2 generation revealing complementary gene interaction involving two genes. Segregating lines from the F2 populations were superior to checks and parental lines in terms of early flowering, early fruiting, fruit length, fruit girth, fruit weight, number of fruits per plant and yield per plant. F2 population raised in the open field condition had more variability than that under the polyhouse. High heritability coupled with high genetic advance as percentage of the mean were recorded for days to flowering, fruit girth, fruit weight, number of fruits per plant and yield per plant suggesting the predominance of additive gene action in inheritance of these traits. Under polyhouse conditions, days to flowering and days to fruiting as well as fruit length and girth under open field conditions exhibited leptokurtic distributions. Conversely, under open field conditions, days to flowering and days to fruiting along with fruit length and girth under polyhouse conditions exhibited platykurtic distributions. Most of the traits except days to flowering and days to fruiting, expressed positively skewed distribution revealing complementary gene action in the expression of those traits. Artificial release of mites was carried out at 30 days after transplanting (DAT) by leaf clipping and scoring of mite resistance was done according to Niles (1980), and Latha and Hanumanthraya (2018) at 45, 60 and 75 DAT. Percentage of leaves exhibiting downward curling symptoms (PLDC) ranged from 4.13 to 83.80 in the F2 generation, whereas it was in the range of 24.37 to 65.84 in the checks. Among the segregating generation, PLDC ranged from 9.01 to 80.79 under the polyhouse condition, whereas it was in the range of 4.13 to 83.80 in the open field. There was no immune genotype in the F2 generation. Based on the PLDC, there were 106 resistant, 281 moderately resistant, 201 susceptible, and five highly susceptible genotypes. Mite population was recorded from the resistant and moderately resistant genotypes at 75 DAT. Total number of eggs and active stages of mites ranged from zero to 13.25/cm2 on leaves of resistant genotypes under the polyhouse. Resistant and moderately resistant F2 plants were selected and forwarded to F3 generation as progeny rows. In the F3 generation, PLDC varied between 3.33 and 89.47. There were significant differences between the progeny rows with respect to PLDC. Based on the PLDC at 75 DAT, selection was carried out within and between the progeny rows. Out of 1260 genotypes in the F3 generation, 129 were resistant and 390 were moderately resistant at 75 DAT. Total number of mite eggs and active stages on resistant plants ranged from zero to 55.00/cm2 at 75 DAT. The resistant lines identified from this study could be used as new varieties or as parents in the hybridization programme after attaining homozygosity.
  • No Thumbnail Available
    Item
    In-situ characterization and DNA profiling of selected genotypes of tamarind (Tamarindus indica L.)
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellanikkara, 2025-04-16) Mrithyunjay Nandakumar; Asna, A C
    Tamarind (Tamarindus indica L.), belonging to the family Leguminosae, is widely utilized in food, traditional medicine, cosmetics, and other industries. It is particularly valued for its acidic pulp as a souring agent. Despite its economic and ecological significance, research on its genetic variability, remains limited, especially in Kerala, the region harbouring unique primitive cultivars such as ‘valanpuli’ and sweet types like ‘madhurapuli’ and ‘thenpuli’. The present study which forms a part of the ongoing state plan was taken up in this background at COA, Vellanikkara during 2022-2025 with the objectives of in-situ characterization and DNA profiling of selected genotypes of tamarind. Thirty steady bearing tamarind genotypes located from three revenue blocks of Palakkad district of Kerala formed the material for the study. These genotypes were subjected to morphological, biochemical and molecular evaluation. The morphological evaluation based on 11 qualitative and 17 quantitative characters was done using the descriptors from established studies (Patil, 2004; Singh, 2010) and Protection of Plant Varieties and Farmer's Rights Authority (PPVFRA,2017) guidelines. TSS, total sugar, titratable acidity, vitamin C, total antioxidant capacity and seed protein were estimated following standard procedures for biochemical characterization. Wide variability was observed among the accessions for all the quantitative traits. Variations expressed by the genotypes in terms of both pod and seed quantitative traits was also high. Among the genotypes, KTJ 166 was having the highest pod weight and pod length. The highest pulp percentage was observed in KTJ 162, while the highest real pulp value (RPV) was recorded in KTJ 164 (10.83). The biochemical characters viz., TSS, total sugar, titratable acidity, vitamin C, total antioxidant capacity and seed protein ranged from 46.35 to 85.97°B, 13.96-41 per cent, 7.59 - 13.27 per cent, 5.12 - 20.93 mg/100 g, 26.50 to 58.36 mg AAE/g and14.43 g/100 g to 19.87 g/100 g, respectively. The sugar-to-acid ratio in tamarind is a good way to differentiate between sweet and sour types. Two genotypes, KTJ 60 and KTJ 48, exhibiting acidity levels below 8 per cent, with total sugar content varying between 36.30-41.00 per cent showed a high sugar acid ratio representing sweet types. Based on organoleptic evaluation, the maximum score for overall acceptability was also obtained for KTJ 48 followed by KTJ 88 and KTJ 66. Agglomerative hierarchical clustering based on quantitative and biochemical characters resulted in five clusters. Clustering clearly separated KTJ 77 and KTJ 162 from other genotypes by placing them in cluster II and III, respectively. High heritability coupled with high genetic gain was observed for pod weight, pod length, pulp percentage, fibre percentage, seed weight, number of seeds per pod, TSS, titratable acidity, ascorbic acid, total antioxidant capacity and total sugar. Pod weight, a crucial determinant of yield, demonstrated significant positive correlation with pod length (r = 0.94), RPV (r= 0.90) seed weight per pod (r = 0.94), and number of seeds per pod (r = 0.71). RPV demonstrated positive correlations with pod weight, pod length, pulp percentage, seed weight per pod and number of seeds per pod. TSS demonstrated a strong positive correlation with total antioxidant capacity. Conversely, titratable acidity exhibited a significant negative correlation with antioxidant capacity (r = -0.735). Principal Component Analysis (PCA), done for the purpose of clustering the accessions, revealed that the first three components explained 88.93 per cent of total variation. From the comprehensive evaluation of PCA analysis and clustering, four genotypes—KTJ 84, KTJ 164, KTJ 166, and KTJ 174—were identified as plus trees with high RPV, while KTJ 48 (41%), KTJ 60 (36.3%), KTJ 77 (39.52%), and KTJ 172 (36.5%) stood out for notable total sugar content. All 30 genotypes were initially screened with 39 random primers, of which all produced reproducible bands except ISSR-835, ISSR-815, (CT)₈T, and (GT)₈GC. The number of bands per primer ranged from 3 to 13, averaging 6.32. ISSR-29 generated the highest number of amplicons (368), while ISSR-22 produced the least (80). The highest polymorphism was observed in ISSR-22 (62.5%), followed by ISSR-18 (56.83%), and ISSR-2 (47.98%), whereas ISSR-30 had the lowest (4.11%). The UPGMA dendrogram generated via NTSYS-pc software using Jaccard similarity coefficients indicated high genetic similarity among accessions. At 60 per cent similarity, 30 genotypes clustered into five groups. KTJ 169 exhibited the greatest genetic distinction, forming an independent branch, indicating some genetic divergence. Among 18 shortlisted DNA markers, seven (ISSR-1(800bp) ISSR-2 (1000bp), ISSR-17 (600bp), ISSR-18 (525bp), ISSR-25 (625bp, 725bp), ISSR-26 (900bp), ISSR-34 (325bp)) effectively detected polymorphism, producing unique bands in KTJ 174, KTJ 51, KTJ 162, KTJ 172, KTJ 169, KTJ 164, and KTJ 89. ISSR 1 (550bp) differentiated KTJ 72 and KTJ 77, while ISSR-1 (700bp) and ISSR-6 (675bp) uniquely identified KTJ 48 and KTJ 60. ISSR-18 (625bp) separated KTJ 48, KTJ 60, and KTJ 170, and ISSR-24 distinguished KTJ 48, KTJ 60, and KTJ 174. ISSR-25 (525bp) effectively differentiated KTJ 48, KTJ 84, KTJ 164, and KTJ 168. The study provides a comprehensive assessment of tamarind genetic diversity through morphological, biochemical, and molecular characterization. Molecular markers identified in this study can facilitate further genetic studies and marker assisted selection in tamarind improvement programs. The findings of this research are expected to contribute to the conservation and improvement of tamarind germplasm for future breeding programs.
  • No Thumbnail Available
    Item
    Screening of tomato (Solanum lycopersicum L.) genotypes for high temperature tolerance
    (Department of Plant Breeding and Genetics, College of Agriculture , Vellanikkara, 2024-05-28) Anjali Joy, S L; Deepthy Antony, P.
    Tomato (Solanum lycopersicum L., 2n=24) cultivation is prevalent in both tropical and sub-tropical climates. For optimum yield and quality, the crop needs a climate that is dry and fairly cold, and are sensitive to hot and humid climate. In the current context of global warming, high temperature is considered as a major threat to agriculture with profound consequences on yield and quality. Plant morphology, physiology, biochemistry, and molecular pathways are disrupted by heat stress. The optimum temperature range for fruiting in tomato is narrow viz., 15 to 21 °C at night and 30 to 35 °C during the day. Depending on the stage of growth, a daily mean temperature between 21 and 24 °C is ideal for tomato. The current study, ‘Screening of tomato (Solanum lycopersicum L.) genotypes for high temperature tolerance’ was conducted during 2021–2023 at the Department of Plant Breeding and Genetics, College of Agriculture, Vellanikkara. Thirteen NBPGR accessions, four hybrids from IIHR, Bengaluru, eight improved lines from the World Vegetable Centre, Taiwan, and five KAU varieties made up the 30 tomato genotypes used in the study. Genotypes were subjected to laboratory screening for thermotolerant traits, and selected genotypes were taken for polyhouse screening. Field screening was done during summer for evaluating the performance of all the genotypes for thermotolerance and yield traits. All experiments were laid out in completely randomized design with three replications for laboratory and polyhouse screening, and two replications for field screening. Physiological traits (electrolyte leakage and membrane stability) and morphological traits (pollen viability, pollen germination, style length and style protrusion) were evaluated under laboratory and polyhouse screening. Plant height and yield characters (days to 50 per cent flowering, fruit set per cent, deformed fruits per cent, number of fruits per plant, average fruit weight and fruit yield per plant) were recorded under field screening along with morphological traits. Arka Samrat, EC 538153, AVTO 1314, and Manuprabha were superior genotypes for electrolyte leakage and membrane thermostability under laboratory screening. EC 528368, EC 620486, Akshaya, and Vellayani Vijay outperformed other varieties in terms of pollen viability and germination at 40 ℃. Superior genotypes based on pollen viability and style protrusion were EC 315489, EC 523851, EC 528368, EC 538153, EC 567305, EC 620486, EC 620488, EC 636872, AVTO 0922, AVTO 1725 and Vellayani Vijay. Based on style protrusion and pollen germination at 40 ℃, and their combination with other traits, 14 genotypes (AVTO 1702, AVTO 1706, AVTO 1725, AVTO 1726, EC 315489, EC 538153, EC 549819, EC 620428, EC 620486, EC 620488, EC 620494, EC 636872, Manulakshmi, and Vellayani Vijay) were selected for polyhouse evaluation. Polyhouse screening was done inside a non-ventilated structure to ensure temperature build up, and an increase of 4-5℃ was found inside the structure compared to ambient condition. All genotypes showed a decrease in pollen viability and germination under polyhouse compared to the open condition. All the genotypes, except Vellayani Vijay showed an increase in style protrusion. Superior genotypes with respect to electrolyte leakage were AVTO 1725, AVTO 1702, AVTO 1706, EC 620428, EC 538153, and Manulakshmi. EC 549819, EC 620428, and EC 636872 were considered as superior genotypes based on style protrusion and pollen germination, as they are important thermotolerant traits. Field screening was carried out to assess the yield traits along with thermotolerant traits in summer season. EC 528360 was found to be superior in pollen viability and style length. Style protrusion increased in all breeding lines and hybrids, except EC accessions. Genotypes like Akshaya, Arka Rakshak, AVTO 1314, and EC 636872 were significantly superior for fruit set percentage compared to Vellayani Vijay. Deformed fruits percentage showed no significant variation between genotypes, and was more than 80 per cent for every genotype examined. Vellayani Vijay and EC 636872 exhibited higher fruit number per plant. Arka Rakshak had a significantly higher average fruit weight than all other genotypes. Pollen viability, style protrusion, number of fruits per plant, fruit set, average fruit weight, and fruit yield per plant all demonstrated high GCV and PCV. The GAM and high heritability of the remaining characters suggested that they had additive gene effects and can be used for selection. Correlation analysis of observations recorded for field screening showed that style length and style protrusion had a significant positive correlation with fruit set per cent, average fruit weight and fruit yield per plant. Molecular markers did not reveal polymorphism in the present study and needs further investigation to identify reliable markers. AVTO 0922, EC 523851, EC 528368, EC 549819, EC 620494, EC 636872, and Vellayani Vijay were identified as heat-tolerant genotypes based on laboratory, polyhouse, and open field evaluations. Akshaya, Anagha, Arka Rakshak, AVTO 0301, AVTO 1314, AVTO 1707, Manuprabha, and Vellayani Vijay had higher yields and, with the exception of AVTO 0301, all had high fruit set percentage in the summer season. In general, thermotolerant genotypes performed moderate to poor in terms of yield traits. Hence, the study demonstrated that specific donors for thermotolerance traits and yield traits needs to be included in crop improvement programmes for heat tolerance in tomato. Vellayani Vijay had heat tolerance traits as well as superior yield traits indicating its suitability for incorporation in crop improvement programmes.
  • No Thumbnail Available
    Item
    Genetic analysis of medium duration rice genotypes for tolerance to iron toxicity in south central laterites of Kerala
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2022-01-22) Anandhu Raj; Bindu, M R
    The present study entitled “Genetic analysis of medium duration rice genotypes for tolerance to iron toxicity in South Central Laterites of Kerala” was conducted at Farming Systems Research Station, Sadanandapuram to evaluate and select rice genotypes tolerant to iron toxicity suited to South Central Laterites of Kerala during 2019-2021. The project was implemented as two experiments and in Experiment-I, initial evaluation of rice genotypes for iron toxicity tolerance was done as pot culture study. In Experiment-II, genotypes selected from experiment-1 was evaluated in paddy field where soil iron is at a toxic level. Thirty rice genotypes were collected from different research stations under KAU. Growing media consist of washed sand in polybags kept in plastic basins filled with Hoagland solution at different concentration (0,200,400,600 mgl-1) of iron at a constant pH of 4.0. Rice genotypes Uma, Karishma, Thekkan chitteni, Pournami, Panchami, Gouri, Bharati, Aiswarya, Asha, Pavithra and Samyuktha were selected from 30 genotypes screened in the laboratory based on morphological characters and iron toxicity score at highest iron concentration (600 mgl-1). Eleven rice genotypes were evaluated in field in iron toxicity affected field with pH (4.9) and iron content (544 mg kg-1), in randomized block design. Germinated seeds were sown in nursery and 21 days old seedlings were transplanted to main field. Seedlings were transplanted at a spacing of 20cm X 15cm. Agronomic practices which include lime application (600 kg ha-1) were carried out according to “Package of Practices Recommendation Crops 2016” of Kerala Agricultural University (KAU, 2016). A control block without lime application containing all treatments were maintained. The genotypes were evaluated for 33 characters including biometric and biochemical characters associated with iron toxicity tolerance. The genotypes showed significant differences for all the characters studied. Genetic parameter analysis was performed for 21 characters and for all the characters PCV values were higher than GCV values indicating the influence of environment. The phenotypic and genotypic coefficient of variation were maximum for straw yield per plant and minimum for days to 50% flowering. High heritability coupled with high genetic advance was observed for plant height, total number of tillers per plant, number of productive tillers per plant, panicle weight, sterility percentage, root length, grain yield per plant, straw yield per plant, number of fresh roots (20 DAT), iron content on root, iron content on 3rd leaf from tip, iron content in oldest fully opened matured leaf, iron content in grain, iron content in straw. Days to 50% flowering, number of tillers per plant, number of productive tillers per plant, panicle length, panicle weight, number of grains per panicle, number of filled grains per panicle, 1000 grain weight, root length and total number of roots (20 DAT) showed positive correlation with grain yield per plant. The path analysis provides information on contribution of traits by partitioning the total correlation into direct and indirect effects. Path analysis revealed highest positive direct effect of days to 50% flowering on grain yield per plant. Highest indirect effect of number of grains per panicle through days to 50% flowering. Cluster analysis aids in the selection of genetically divergent parents for hybridization programme which results in greater heterosis. Cluster analysis using Mahanalobis D2 statistic following Tocher’s method grouped the 11 genotypes into five clusters.Cluster I with 7 genotypes was the largest and cluster II, III, IV, V were solitary. Intra cluster distance was recorded only in cluster I (11.32). Highest intercluster distance observed between genotypes of cluster V and cluster II. The present study revealed that genotypes Panchami (6.4 t/ha) recorded maximum yield and was followed by Pournami (5.7 t/ha). These varieties can be recommended for iron toxic low land paddy fields of South Central Laterites of Kerala. Genotypes Panchami, Pournami, Uma, Karishma, Gouri and Pavithra recorded lowest leaf bronzing score at maturity under iron toxic field conditions. These genotypes can be used in breeding programmes to develop iron toxicity tolerant rice varieties.
  • No Thumbnail Available
    Item
    Physiological, biochemical and molecular characterization of saline tolerant genotypes of rice
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2022-03-11) Bindhya Mathew; Veena Vighneswaran
    The study entitled “Physiological, biochemical and molecular characterization of saline tolerant genotypes of rice” was conducted at Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, during 2019-21 to screen saline tolerant rice genotypes of Kerala for the presence of Saltol QTL and to assess various physiological and biochemical parameters of salt tolerance under different stress levels. Twenty rice varieties, including one susceptible check were grown in nutrient media and soil whose electrical conductivity was maintained at three different levels viz, 6 dS m-1, 9 dS m-1 and 12 dS m-1. Experiment was conducted in two parts. Visual scoring and molecular screening were done on the genotypes in the first part and physiological and biochemical characterization of their saline tolerance were performed in the second part. For visual scoring, rice seedlings were grown hydroponically in seedling floats containing salinized Yoshida nutrient medium, for 21 days. Molecular screening was done using 20 SSR markers linked to the Saltol QTL of rice. For physiological and biochemical characterization, the genotypes were grown in pots, with soil maintained at EC of 6 dS m-1, 9 dS m-1 and 12 dS m-1. Various morphological, biometrical, physiological and biochemical parameters of salt tolerance were studied. Observations were taken at 5 stages- 21st day (seedling stage), 40th day (active tillering), 60th day (panicle initiation), at flowering and at harvest stage. On analysis of the binary marker data in NTSYSpc for genetic distance, it was found that the genotypes were diverse in terms of marker alleles and they clustered into 4 groups. The released varieties and the traditional saline tolerant landraces of Kerala are highly related and got clustered under one group. The CSR varieties were more related to FL 478, than the varieties from Kerala. Jyothi, was very unrelated to other varieties and formed a separate group. All tolerant varieties except CSR 10 and CSR 27 were polymorphic with FL 478 for atleast one of the three important markers linked to Saltol - RM1287, RM493 and RM10748, revealing that a salt tolerance mechanism other than that controlled by Saltol QTL might be in action within them. The morphological, physiological and biochemical parameters under study showed a significant variation among genotypes and treatments. The interaction between genotypes and salinity levels was significant for the observations on number of tillers per hill, grain yield, plant height, root length, fresh weight of shoot and root, dry weight of shoot and also for all biochemical parameters- chlorophyll content, sodium content, potassium content, Na+: K+ ratio, proline content and activities of catalase, peroxidase and superoxide dismutase. For all these parameters the susceptible variety showed significantly high/low values compared to the tolerant varieties except in plant height at 12 dS m-1, root length at 9 dS m-1 and 12 dS m-1, and chlorophyll content in all treatments on 21st day, 40th day and in 6 dS m-1at 60th day. Cluster analysis revealed that the genotypes clustered in a similar fashion based on the biochemical observations from 21st and 40th day, but a much different clustering was observed in 60th day, opening the possibility for a different kind of tolerance mechanism working at reproductive stage. As observed from the results of principal component analysis, at seedling stage and active tillering stage, Na+: K+ ratio had the greatest contribution to salt tolerance but at panicle initiation stage, it was the peroxidase activity. The percentage contribution of Na+ and K+ contents on the principal component 1 of salinity tolerance had reduced and that of peroxidase activity and superoxide dismutase activity increased, as the plants transitioned from seedling and tillering stage to the panicle initiation stage. Combining this observation with the polymorphism of genotypes for the important markers of Saltol, it was concluded that there could be an alternate mechanism and a genomic region, possibly a QTL, providing reproductive stage salinity tolerance to genotypes.
  • No Thumbnail Available
    Item
    Pedigree selection for spotted pod borer resistance in the segregating generation of Cowpea (Vigna unguiculata (L.) Walp.)
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellanikkara, 2022-09-19) Minnu Thomas.; Jiji Joseph
    Cowpea [Vigna unguiculata (L.) Walp.] is an important pulse crop grown across the world mainly in tropical and subtropical regions. Being a drought-tolerant and warm-weather crop, it is a promising food and forage species in a typical tropical lowland climate. Low productivity in cowpea is mainly attributed by the severe attack of pest complexes, diseases, low fertile soils and lack of inputs. Among the various obstructions responsible for diminishing the production of cowpea, the predominant factor is the damage caused by insect pests. Among the various insect pest causing economic losses, the spotted pod borer, Maruca vitrata (Lepidoptera: Crambidae) acts as the most damaging one. Hence, the present investigation was conducted in the Department of Plant breeding and Genetics, College of Agriculture, KAU, Vellanikkara with the objective of Pedigree selection from early segregating generations of cowpea hybrids for resistance against spotted pod borer. Ambavane (2018) identified that ten superior F2 lines from the cross Vellayani Jyothika × EC 98668 were resistant to spotted pod borer. The present study involved the reconstitution of the above cross and the pedigree analysis of resultant segregating material. Through hybridisation between Vellayani Jyothika and EC 98668, ten hybrid plants were produced. These hybrids were evaluated on morphological basis for resistance. Seeds from F1 hybrid were then sown to raise the F2 population. A population size of 500 plants was maintained in the F2 population and individual plant observations were taken for analysing their quantitative characters. The F2 population showed high variability for the characters like days to 50 per cent flowering, plant height, no. of pods per plant, pod length and grain yield per plant. However, low variability was observed in characters like no. of primary branches per plant, no. of seeds per pod and 100 seed weight. Selection was not carried out in the F2 population and the seeds were forwarded to raise the next generation. The genetic variability studies of the F2 population revealed that high PCV, GCV, heritability and GAM was recorded for characters like pod length, grain yield per plant and 100 seed weight. In F3 population, morphological and biochemical observations was carried out with the objective to select superior lines showing resistance to pod borer. The F3 population showed reduced variability for all quantitative characters except No. of seeds per pod compared to F2 population. The genetic variability studies of the F3 population also showed a similar trend like F2 population and showed high PCV, GCV, heritability and GAM for characters like pod length, grain yield per plant and 100 seed weight. Analysis of morphological basis of resistance to pod borer revealed a negative correlation of pod wall thickness, trichome density on pod and bud with pod damage. With respect to the biochemical basis of resistance to pod borer, total sugar content and total protein content showed significant positive correlation with pod damage. However, total phenol content and polyphenol oxidase activity was found to be negatively correlated with pod damage and the correlation was non-significant. Based on the correlation study and taking into account of the work of earlier studies, it is evident that the biophysical characters like pod wall thickness, pod trichome density, bud trichome density and biochemical characters like total sugar content, total protein content, total phenol content and polyphenol oxidase activity are highly associated with spoted pod borer resistance. Based on these results, a selection criteria was fixed. Thirty superior plants from F3 population were selected. These plants could be further evaluated to identify high yielding resistant lines.
  • No Thumbnail Available
    Item
    Development of dual purpose fodder Cowpea [Vigna unguiculata (L.) Walp] through mutagenesis
    (Department of Plant Breeding and Genetics, College of Agriculture , Vellayani, 2021-12-21) Arya S Nair; Gayathri, G .
    The present study entitled “Development of dual purpose fodder cowpea [Vigna unguiculata (L.) Walp] through mutagenesis” was conducted in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 2019-2021. The study was conducted to induce mutation in fodder cowpea, variety Aiswarya with Ethyl Methane Sulphonate and to select superior dual purpose genotypes for seed and fodder from the mutants. The study was carried out in three experiments. In the first experiment, seeds of fodder cowpea variety Aiswarya were treated with five different doses of EMS. Observations were recorded on seed germination per cent and seedling survival per cent. Germination percentage and seedling survival percentage reduced with an increase in the concentration of the mutagen. Based on the seedling survival percentage, LD50 value were determined. Effective doses were fixed as 0.35%, 0.39%, 0.43%, 0.47% and 0.51% according to the LD50 value. In experiment II, seeds were treated with the effective doses of EMS and M1 plants were evaluated. Observations were recorded on seedling emergence (%), seedling survival at branching stage (%), and plant survival up to maturity (%) and these characters varied significantly among the treatments. Presence of chimera and chlorophyll mutants was also observed. Presence of chlorophyll mutants were noted in the population of all mutagenised treatments. Seeds from M1 generation constituted M2 population. M2 generation was observed for various quantitative characters including number of primary branches per plant, number of leaves per plant, days to first flowering, days to 50% flowering, green fodder yield per plant, dry matter yield per plant, leaf stem ratio, leaf dry weight per plant, stem dry weight per plant, leaf area index, plant height, seed yield per plant and days to maturity and qualitative characters like early plant vigour, plant growth habit, leaf texture, leaf colour, flower colour, seed colour and presence of chlorophyll mutants. Significant variations were found in all quantitative characters except plant height and leaf stem ratio. Among these, number of primary branches per plant, number of leaves per plant, green fodder yield per plant, dry matter yield per plant, leaf dry weight per plant, stem dry weight per plant and leaf area index were higher in 0.43% EMS treatment. Seed yield was found higher in control, which was on par with 0.51% EMS and followed by 0.43% EMS treatment. In qualitative characters, seed colour and plant growth habit showed remarkable variation, whereas early plant vigour, leaf texture and leaf colour exhibited slight variations. Flower colour did not show any variations. Comparing with M1, frequency of chlorophyll mutants in M2 was lesser. For fodder purpose, 0.43% EMS treatment expressed higher fodder yield. In case of seed yield, 0.51% was recorded with higher seed yield, followed by 0.43% among the mutants. It was concluded from the present investigation that, for fodder cowpea variety Aiswarya, which was treated with different concentration of EMS and 0.43% EMS treatment was found effective to obtain superior genotypes for seed and fodder yield from mutants.
  • No Thumbnail Available
    Item
    Morphological and biochemical characterization of Brinjal (Solanum melongena L.) ge
    (Department of Plant Breeding and Genetics, College of Agriculture, Padannakkad, 2022-05-21) Alan Thomas.
    The study entitled “Morphological and biochemical characterization of brinjal (Solanum melongena L.) genotypes” was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Padannakkad during 2019-2021. The study was conducted in two experiments and the objectives were to characterize the brinjal genotypes based on morphological, biochemical and quality characters; analyze the genetic variability in collected accessions and to identify best genotypes having high yield, superior quality as well as resistance/ tolerance to fruit and shoot borer. The experimental material consisted of two wild species (S. insanum and S. incanum) and twenty eight S. melongena accessions including collections from North Kerala (Kannur-5, Kasaragod-4, Malappuram-1), accessions from NBPGR regional station, Thrissur as well as KAU released varieties (Ponny, Haritha and Surya). The first experiment was laid out in a randomized block design with 30 genotypes in three replications and observations were recorded for 12 qualitative, 18 quantitative and 8 fruit quality and biochemical characters. The analysis of qualitative characters showed wide variation for corolla colour and fruit characters such as curvature, shape, apex shape, pedicel and calyx prickles, flesh density, fruiting pattern and colour. The results of analysis of variance revealed significant differences for all the quantitative characters indicating presence of high genetic variability. The brinjal genotypes SM-1, SM-5 and SM-11 showed superiority for percent medium and long styled flowers (67.59%, 42.78%, 61.75%), fruit setting percentage (63.89%, 37.59%, 55.45%), days to first harvest (61.33, 63.67, 61.67), fruit weight (111.18g, 115.28g, 106.87g) and marketable fruit yield (1874.67g, 1619.67g 1673.33g). The variance component analysis revealed high heritability coupled with high genetic advance as per cent of mean for all the fruit and yield characters as well as pericarp thickness, anthocyanin in fruit peel and vitamin C indicating that most likely the heritability is due to additive effects making selection effective based on these characters. Correlation and path analysis revealed that fruit setting percentage, days to first harvest, fruit weight and number of fruits per plant showed significant genotypic correlation and direct effect depicting true association of these characters with fruit yield. Selection based on these characters will help to achieve efficient improvement in fruit yield. The UPGMA clustering of 30 eggplant accessions for qualitative traits revealed six groups based on fruit curvature, corolla colour, fruit shape, fruit apex shape, fruit flesh density, fruit colour. The genetic diversity analysis based on Mahalanobis D2 statistics for 18 quantitative characters grouped 30 accessions into thirteen clusters. The character fruit weight contributed maximum towards diversity. The maximum intra-cluster distance was reported in cluster V followed by cluster IV. The highest inter-cluster distance was recorded between cluster VII and XII followed by clusters VII and VIII indicating a wide range of diversity between these clusters providing scope for hybridization between superior genotypes of these highly divergent clusters. The accessions SM-1, SM-2, SM-5, SM-9, SM-10 and SM-11 showed superior ranking in their respective clusters based on three yield attributes viz., fruit weight, fruit setting percentage and marketable fruit yield identified in association and divergence analysis. In the second experiment brinjal accessions were screened for resistance to fruit and shoot borer in a completely randomized design in three replications. The observations were recorded for percentage of shoots infested and percentage of fruits infested at ten days intervals and the accessions were grouped into six categories based on severity of damage on fruits. Wild accessions SM-26 (S. incanum) and SM-27 (S. insanum) were found to be immune, as none of these plants showed symptoms of infestation. SM-6 and SM-7 were rated as highly resistant accessions. SM-1, SM-2, SM-3, SM-4, SM-5, SM-8, SM-9, SM-11, SM-14 and Haritha were found to be moderately resistant. SM-10, SM-13, SM-20, SM-22, Ponny and Surya were grouped as tolerant. All the remaining accessions were susceptible. Correlation studies between fruit infestation by fruit and shoot borer with biochemical characters revealed a positive significant correlation of fruit infestation with total sugars and protein content while a negative correlation of fruit infestation was obtained with solasodine content as well as phenol content. The present study resulted in identification of a fair number of high yielding resistant lines amongst the wide collection of indigenous brinjal germplasm used. The wild relatives from highly divergent clusters like cluster I (SM-26), cluster VIII (SM-27) and S. melongena accessions SM-6 and SM-7 can be exploited for their shoot and fruit borer resistance. Accessions SM-1, SM-2, SM-5, SM-9, SM-10 and SM-11 with higher nutrients (protein >1.22 g/100g and vitamin C >5.03 mg/100g), a balance of biochemical content (solasodine and phenol) in addition to high fruit yield (~1300g to ~2100g) and comparatively lesser infestation of fruit and shoot borer can be considered as the promising parents in future crop improvement programs