PG Thesis

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    Evaluation of Chilli (Capsicum annuum L.) genotypes for yield, bacterial wilt and leaf curl virus incidence
    (Department of Vegetable Science, College of Agriculture , Vellanikkara, 2024-05-21) Suvarna, K; Anitha, P
    Chilli is one of the important vegetable spice cultivated worldwide and is commonly referred to as red pepper or hot pepper. It is a crucial commercial crop utilized as a vegetable, spice, condiment and culinary flavour enhancer. Chilli is mainly used as culinary supplement to add flavour, colour and pungency. Chilli is an abundant source of vitamin A and C. Capsaicin and its related compounds present in the placental tissue of its fruits is used in pain relieve balms and vapour rubs. The green fruits of chilli stand out as one of the most plentiful sources of antioxidants. Despite its considerable nutritional value, widespread acceptance among consumers and extensive genetic diversity, achieving optimal productivity in chilli production remains a challenge due to lack of high-yielding and disease-resistant varieties or hybrids. In addition, diseases like chilli leaf curl virus and bacterial wilt are the most two important diseases affecting chilli production. In this context, the current study was initiated with the objective of assessment of morphological traits of chilli genotypes for yield to identify high yielding ones and to simultaneously evaluate these genotypes against bacterial wilt and leaf curl virus incidence. The present study was conducted in the Department of Vegetable Science, College of Agriculture, Vellanikkara during January 2023 to May 2023, using 31 chilli genotypes. The analysis of variance among the 31 genotypes of chilli revealed significant variations across all the traits. Genetic parameters such as Genotypic Coefficient of Variation (GCV), Phenotypic Coefficient of Variation (PCV), heritability and Genetic Advance (GA) were computed to assess the extent of variability. High GCV and PCV were exhibited by the characters like plant height, fruits per plant, average fresh fruit weight, average dry fruit weight, fruit length, fruit girth, pedicel- fruit ratio, yield per plant, bacterial wilt incidence, incidence of leaf curl virus, oleoresin content, capsaicin content, ascorbic acid content. The results indicated that the presence of a broad genetic base which will be useful in further selection. High heritability coupled with high genetic advance was reported in most of the morphological and quality characters indicating that these characters are under the influence of additive gene action. Therefore, it is feasible to apply direct selection for improving these traits. Correlation studies indicated that fruit yield per plant was significantly and positively correlated with plant height, primary branches per plant, fruits per plant, average fresh fruit weight, average dry fruit weight, fruit length, pedicel length, oleoresin content, capsaicin content and ascorbic acid content. Interrelationships among plant traits is crucial for enhancing both yield and quality. Hence, simultaneous selection for these characters would be advantageous for enhancing chilli yield. Path coefficient analysis among yield and its constituent traits indicated that the fruits per plant, average fresh fruit weight, days to harvest, pedicel length, fruit girth and plant height showed direct positive influence on yield. Path analysis reveals whether the correlation between yield-related traits and yield is having direct effect, in which case direct selection for improvement is possible. From the present study, based on the path coefficient and correlation results the genotypes CA 1, CA 3, CA 6 and Ujwala were recognized as promising or advantageous. The 31 chilli genotypes were categorized into eleven clusters using Mahalanobis D2 statistic. Cluster I contained the largest number of genotypes (21), followed by cluster II, cluster III, cluster IV, cluster V, cluster VI, cluster VII, cluster VIII, cluster IX, cluster X and cluster XI which had one genotype each. The intra-cluster distance was the highest in cluster I, while the inter-cluster distance was the greatest between cluster IV and cluster IX. Hence, selecting genotypes for hybridization or developing hybrids, genotypes from these two clusters should be prioritized. The selection index for chilli was established based on the characters including fruit yield per plant, fruits per plant, average fresh fruit weight, incidence of leaf curl virus and bacterial wilt incidence. Among the genotypes evaluated, CA 3, CA 6, CA 1 and Ujjwala were identified as the top performers. Notably, genotypes CA 3, CA 6 and CA 1 exhibited superior performance in terms of yield and leaf curl virus resistance when compared to Ujwala.
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    Evaluation of brinjal (Solanum melongena L.) genotypes for resistance to bacterial wilt (Ralstonia solanacearum)
    (Department of Plant Breeding and Genetics , College of Agriculture, Padannakkad, 2023-12-11) Muslepally Niharika; Namboodiri Raji Vasudevan
    The current study entitled “Evaluation of brinjal genotypes for resistance to bacterial wilt (Ralstonia solanacearum)” was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Padannakkad during 2020-2023. The main objectives of the study were to evaluate brinjal genotypes for resistance to Bacterial wilt (BW) and examination of the mechanism of resistance through anatomical and biochemical parameters as well as estimation of yield characters in resistant lines. The experimental material consisted of thirty-one accessions which included eleven accessions (SM-1, SM-2, SM-3, SM-4, SM-5, SM- 8, SM-9, SM10, SM-31, SM-32, SM-33) collected from North Kerala, seventeen accessions (SM-11 to SM-27) from NBPGR. It also included three released varieties and hybrid of KAU (Haritha, Surya, Ponny and Neelima) as resistant checks and two susceptible checks (SM-26[S.incanum] and SM-27[S.insanum]). In experiment I, three weeks old seedlings of all brinjal genotypes were screened for resistance to BW in a completely randomized design with three replications. Based on percentage disease incidence (PDI), two accessions SM-15 and SM-25 were rated as highly resistant (HR: 0 PDI) and accessions SM-1 was rated as resistant (R: 1-10 PDI). Accessions SM-1, SM-2, SM-5, SM-11, SM-17, SM-24 and KAU hybrid Neelima were rated as moderately resistant (MR: 11-20 PDI). Accessions SM-4, SM-8, SM-14 and SM-19 were rated as susceptible (S: 21-30 PDI). Moderately susceptible (MS: 31-40 PDI) accessions were SM-3, SM-32, SM-33, SM-13 and SM-16. Accessions SM-9, SM-10, SM-12, SM 18, SM-20, SM-21, SM-22, SM-23, SM-26 and SM-27 were rated as highly susceptible (HS: >40 PDI). Biochemical parameters viz., Polyphenol oxidase (PPO) enzyme activity, total phenols, and total sugars (both reducing and non-reducing) were assessed at 12 and 24 hours post inoculation (hpi).In this analysis using twenty two accessions consisting of eight genotypes from resistant categories (HR, MR, R) and eight from HS group along with four RC ( Ponny, Haritha, Surya and Neelima) as well as two SC (SM-26, SM-27) were used. A control group with mock inoculation was also part of the analysis. Two factor ANOVA demonstrated significant differences in these biochemical parameters among all tested brinjal genotypes. At 12 and 24 hpi, the most significant rise in PPO activity was observed in the RC followed by the R group, HR germplasm and MR group compared to their respective control samples. Moreover at 24 hpi the resistant (R) genotypes exhibited a significant 3.5-fold increase in PPO activity compared to the control group. Resistant checks exhibited the highest phenolic content followed by the HR, R and MR germplasm at 12 and 24 hpi. The highest amount of total sugars, which includes both reducing and non-reducing sugars, was observed in RC followed by HR germplasm, R germplasm, and MR germplasm after 24 hpi. Correlation analysis revealed a significant negative correlation between biochemical parameters viz., PPO enzyme activity, total phenol content, total sugars including non-reducing sugars (12 and 24 hpi) and disease incidence. A positive correlation was observed between disease incidence and reducing sugars at 12 hpi whereas, negative correlation was observed between the same at 24hpi. The biochemical analysis indicated that PPO and phenols played a positive role in the resistance against R. solanacearum in brinjal. However, the role of sugar content in plant defense is still unclear and requires further studies for a better understanding of sugar metabolism. In the current study different aspects of the stem vascular anatomy viz., number of small and large vessels, total number of vessels, ratio of large to small vessels and average vascular area in the eggplant germplasm and correlation of these characters with disease incidence were analysed. A significant variation for anatomical characters was observed among all the genotypes. Among the germplasm HR accessions SM-15, SM-25 and R accession SM 1 showed highest number of large vessels, higher ratio of large vessels to small vessels and higher average vascular area compared to all other accessions. These anatomical parameters are found to play a significant role in the temporal and spatial distribution of the pathogen within the vascular vessels. After analyzing the response of various brinjal genotypes to disease incidence, as well as considering biochemical and anatomical parameters, it was observed that eight genotypes (SM-1, SM-2, SM-5, SM-11, SM-15, SM-17, SM-24, and SM-25) exhibited resistance against BW. These genotypes along with four KAU released resistant checks were further evaluated in the field in experiment II. Field evaluation was carried out in a randomized block design with three replications for sixteen quantitative and two qualitative characters. Per se performance of all genotypes revealed significant variation for all the quantitative characters indicating presence of high genetic variability. Association analysis revealed that leaf area, root dry weight and average fruit weight showed significant positive genotypic correlation and direct effect depicting true association of these characters with fruit yield. Selection based on these characters will help achieve efficient improvement in fruit yield. Among the local accessions, resistant accession SM-1 exhibited the maximum early fruit yield of 972.68 g followed by the Moderately resistant accession SM-11 (965.77 g). Accession SM-1 was also superior for plant height, earliness, average fruit weight and SM-11 for number of fruits per plant. Therefore, resistant accession SM-1 could be regarded as a promising genotype for potential release as a new variety. Highly resistant accessions SM-15 (oval green fruits with intermediate calyx prickles) and SM-25 (oval purple fruits and no prickles on the calyx), displayed excellent plant and flower characteristics like stem girth, branching, days to first and 50 per cent flowering but reported lower early yields. These can be used in hybridization programs either as parents to develop F1 hybrid or as recombinants in recombination breeding for resistance to bacterial wilt.
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    Evaluation of tomato (Solanum lycopersicum L.) hybrids for yield and bacterial wilt resistance
    (Department of Olericulture, College of Agriculture, Vellayani, 2017) Shashidhar M Sonnad; Sarada, S
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    Performance of cherry tomato (Solanum lycopersicum L. var. cerasiforme (Dunal) A.Gray) genotypes in rain shelter and open field
    (Department of Olericulture, College of Horticulture, Vellanikkara, 2017) Malavika, O; Indira, P
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    Evaluation of african marigold (Tagetes erecta L.) hybrids/ varieties for yield and resistance to bacterial wilt
    (Department of Floriculture and Landscaping, College of Horticulture, Vellanikkara, 2017) Umesh, C; Sreelatha, U
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    Development of a molecular marker for bacterial wilt resistance in brinjal ( Solanum melongene L.) varieties Surya and Swetha.
    (Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2011) Somya, P P; Valsala, P A
    The study entitled ‘Development of a molecular marker for bacterial wilt resistance in brinjal (Solanum melongena L.) varieties Surya and Swetha’ was carried out at the Centre for Plant Biotechnology and Molecular Biology (CPBMB), College of Horticulture, Vellanikkara during the period 2009-2011. Bacterial wilt caused by Ralstonia solanacearum (Smith) Yabuuchi et al. is one of the important problems of brinjal cultivation in warm humid tropics. The loss due to this varies from 30-100 per cent. Use of chemicals and field sanitation are not sufficient for controlling the disease. Worldwide approach is to use resistant varieties. KAU has developed and released bacterial wilt resistant brinjal varieties for cultivation. The Surya and Swetha are two among them and have received bacterial wilt resistance from SM-6 an Annamalai collection. This investigation was taken up to develop a molecular marker for bacterial wilt resistance in Surya by RAPD through bulk segregant analysis as reported by Michelmore et al (1991). It also aimed to test the suitability of the same for identifying bacterial wilt resistance trait of resistant variety Swetha. The genotypes used for the study were Surya, Pusa Purple Long (susceptible variety released from IARI), Swetha and F2 population of the cross between Surya and Pusa Purple Long. To raise segregating F2 population F1 was raised by controlled crossing of Surya with pollen grains of Pusa Purple Long. Then F1 plant was selfed to get F2 population. Two different methods viz., stem puncturing and soil drenching with root wounding were compared for the delivery of inoculum of R. solanacearum for bacterial wilt incidence and stem puncture method was found as the best. So stem puncturing method was used for phenotyping of genotypes for bacterial wilt incidence. The F2 population along with Surya, Pusa Purple Long and F1 were phenotyped for bacterial wilt incidence. This was done through artificial inoculation with Ralstonia solanacearum by stem puncture method. Confirmation was done by ooze test. The genotypes were classified according to classification of Mew and Ho (1976). The variety Surya was resistant and Pusa Purple Long was susceptible. F1 population showed 90 per cent susceptibility while F2 population showed 83 per cent susceptibility. They were classified as susceptible. Five resistant and five susceptible genotypes from F2 were selected for bulk segregant analysis. Genomic DNA for RAPD analysis was isolated by Rogers and Bendich method (1994). Good quality DNA with an absorbance ratio of 1.8-2.0 was used for RAPD analysis.PCR reaction mixtures and conditions for DNA amplification were standardised. Ninty two, 10-12 bp primers belonging to OPA, OPB, OPC, OPF, OPE, OPU, OPH, OPAH, OPAG, OPL, OPM, RY, RN, RA, SC, RF, AG 8, WG 44, GLE11, RF, R10, R6, and PUC101 were initially screened with resistant genotype Surya and susceptible genotype Pusa Purple Long to select primers with polymorphism and good amplification. Out of ninty two primers tested thirty were reported as bacterial wilt specific. The PCR products were electrophoresed and twenty two primers were selected for BSA based on amplification power and polymorphism. They were RY 01, RY 02, RY 03, RN 19, OPF 5, OPL 04, OPA 04, OPA 6, OPA 9, OPA 24, OPA 26, OPA 34, OPA 36, OPS 9, OPS 10, OPS 16, OPS 17, PUC 101, RA 12-41, and RF. Among these only the primer RY 02 recorded polymorphism between resistant and susceptible variety with an amplicon of 1.2kb. In bulk segregant analysis DNA of Surya, Swetha, Pusa Purple Long and bulk DNA from resistant genotypes and susceptible genotypes were amplified with selected primers and products were electrophoresed. All primers produced only monomorphic band. None has produced unique polymorphic bands capable of differentiating resistant and susceptible genotypes. This may be due to low polymorphism at genomic level.