PG Thesis
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Item Genetic divergence in kiriyat (Andrographis paniculata Nees)(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2017) Prathibha, S S; Arya, KItem Genetic analysis in F2 And F3 progenies of selected crosses of rice varieties of diverse origin(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2000) Faseela, K V; Rajan, SThe research project 'Genetic Analysis in F2 and F3 Progenies of Selected Crosses of Rice Varieties of Diverse Origin' was carried out in the College of Horticulture, Kerala Agricultural University, Vellanikkara, Thrissur durinq the period January to December, 1998. The major objectives of the study were to understand the various genetic parameters of characters under study, identification of yi&ld components and formulation of selection model so as to isolate promising lines having desirable ideotypic features • from the segregating generations. The high yielding varieties developed from such lines will have a broad genetic base as the parents of selected crosses are of diverse origin. Components of heritable variation revealed that the characters showed decreased trend of variability from F2 to F3. PCV was higher than GCV in both generations for all the characters studied. Low PCV and GCV were observed for grain length, panicle length and duration to 50% flowering in both generations, while grain density showed low PCV and GCV in F3 only. In general, broad sense heritability estimates were observed to be higher in F2 than F3. The characters, plant height at harvest, total tillers plant", LIB ratio, 1000 grain weight, secondary branches panicle' and tertiary branches panicle:' provided great help in direct selection from phenotypic performance, as they exhibited higher values of genotypic coefficient of variation, heritability and expected genetic advance. The .. character, grain length showed little scope of improvement through selection due to low GCV and GA . • Correlation studies in F2 and F3 revealed that positive correlation existed between yield and component characters, namely, total tillers, panicle bearing tillers and tertiary branches panicle". Negative correlation was observed for 1000 grain weight with yield in both the generations. Panicle length and duration to 50% flowering exhibited absence of association with yield in F2 and F3, which indicate that these traits can be recombined as desired. In F3, LIB ratio and grain length exhibited positive correlation and grain breadth exhibited negative correlation, with yield, while these characters showed absence of association with yield in F2• Plant height and number of grains panicle:' exhibited negative association with yield in F2 where as number of grains panic!e' exerted positive association with yield in F3 and plant height showed absence of association with yield in F3. Genotypic correlation among di~ferent yield components in F2 and F3 revealed that semidwarf plants with higher number of productive tillers produced grains with higher LIB ratio and lesser grain weight, which in turn increased the yield. The study also showed that, when number of grains and compactness of• panicles increase, grains become more slender with reduced grain weight. Study of path coefficient analysis revealed that all the characters influenced the yield directly or indirectlv through some other traits. The correlation and path analysis study suggested that during selection, breeder should give emphasis on" semidwarf olant stature, higher number of productive tillers, compact panicles, reduced number of secondary branches, high LIB ratio of grains with reduced density and weight. A selection model was formulated consisting of the characters, , namely, yield ha:'. total tillers plant". LIB ratio, grain breadth and grain density. Using this model, ranking of 105 genotypes in F3 was done and identified that the accessions, V 82 and V 89' belonging to lA 36 x Mattathriveni, were the best genotypes. Study revealed that all the four crosses namely, Vytilla 3 x Mattathriveni, Vytilla 3 x Kaohsiung Sen Vu 338, Mattathriveni x Mahsuri and lA 36 x Mattathriveni, were promising enough to derive superior segregants, the best among them being IR 36 x Mattathriveni. The plants with red kernel, identified in F3 of the cross IR 36 x Mattathriveni, can be used for the development of high yielding varieties with red kernel and preferable cooking qualities suited to Keralites, as well as resistance to biotic and abiotic stresses. This investigation also suggested that crosses from parents of diverse origin will broaden the genetic base of the varieties to be developed in future and will help to break the yield plateau in rice.Item Breeding for lodging resistance in rice (Oryza sativa L.)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2019) Keerthiraj, B; Biju, SThe research work ‘Breeding for lodging resistance in rice (Oryza sativa L.)’ was conducted in the Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, during the academic year 2017-2019. The research work was divided into three experiments. Experiment 1, consisted of screening of twenty-one rice genotypes for lodging resistance which was conducted at Agricultural Research Station (ARS), Mannuthy. After screening, three lodging resistant rice genotypes were selected and crossed in Line x Tester pattern with four lodging prone high yielding varieties, in experiment 2. In experiment 3, progenies were evaluated along with parents for lodging resistance. Lodging and other characters were measured based on Standard Evaluation System of Rice, developed by International Rice Research Institute (SES-IRRI), 2014. Wide variability existed among twenty-one genotypes for yield and most of the yield attributes studied, indicating ample scope for the improvement through selection. High heritability coupled with high genetic advance as per cent of mean indicating the influence of additive gene action in the expression of trait were observed for all the traits viz., days to fifty per cent flowering, plant height, flag leaf width, flag leaf length, tillers per plant, internodal length, culm diameter, culm wall thickness, days to maturity, panicle length, panicles per plant, panicle weight, seeds per panicle, test weight, silicon content, potassium content, seed yield per plant, and lodging per cent. Seed yield per plant recorded positive correlation at genotypic level with number of tillers per plant, number of panicles per plant, test weight, and silicon content. Lodging per cent exhibited positive correlation at genotypic level with days to fifty per cent flowering, plant height, flag leaf length, internodal length, culm diameter, days to maturity, and panicle length. At the same time, it was negatively associated with culm wall thickness, silicon content and potassium content. Based on experiment 1, four genotypes viz., Swetha (L1), Prathyasha (L2), Vaisakh (L3) and Ponmani (L4) were selected as lines. Three genotypes viz., Uma (T1), Gouri (T2) and Pournami (T3) were selected as testers. Evaluation of hybrids based on mean performance revealed that, hybrids H3, H5, H6, H9, and H12 recorded reduced lodging and H7, H8, H10, and H11 recorded moderate lodging. Based on scoring, for all the characters, the hybrids H1 (L1 x T1), H3 (L1 x T3), H5 (L2 x T2), H7 (L3 x T1), H8 (L3 x T2), H10 (L4 x T1), H11 (L4 x T2), and H12 (L4 x T3) showed high values. Estimation of gca effects of parents indicated that, L4, T1 and T3 were better combiners for reduced lodging. Based on all eighteen characters, L4, T1 and T2 were found as better combiners. Considering the scores, of mean performance and combining ability effects for all the characters together, L4, T1, T2, and T3 were found as the most promising parents. Specific combining ability effects studied among the cross combinations and scores indicated that, out of the twelve hybrids, H3 recorded high lodging resistance, and except H1 all others recorded moderate lodging resistance. Based on all the characters considered together, H1, H3, H5, H6, H8, and H10 recorded as better cross combinations. When scores of mean performances and sca effect were considered together for all the characters, hybrids H1, H3, H5, H8, H10, and H11 had high scores, and H6, H7, and H12 scored moderate scores. All the twelve hybrids recorded high significant heterosis for days to fifty per cent flowering, plant height, days to maturity, internodal length and lodging per cent. Scoring for both mean performance and heterotic effect for all the characters, revealed that, the hybrids H12 recorded highest score followed by H10, H11, H8, H3, H5 and H1. Evaluation of hybrids based on scores of mean performances, sca effects and heterosis for all the traits, revealed that, hybrid H10 stands in first position, H8 in second and H11 and H5 in third position. Among these, H10 (Ponmani x Uma) and H11 (Ponmani x Gouri) were found as better cross combinations. The identified hybrids can be evaluated in segregating generations for yield and reduced lodging.Item Performance analysis of vegetable soybean (Glycine max L.) in humid tropics(Department of Vegetable Science,College of Horticulture, Vellanikkara, 2018) Shilpashree, N; Nirmala Devi, SItem 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, SItem Genetic stock development for phytophthora pod rot disease resistance in cocoa (Theobroma cacao L.)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2017) Veeresh S Akki; Minimol, J SCocoa production is ruthlessly affected by pod rot disease caused by many Phytophthora species. Among these, the pod rot caused by Phytophthora palmivora is of prime importance. Since, the disease infection period is rainy season, the application of fungicides has not evidenced as a successful control measure. Hence, the effective and eco-friendly way to tackle this disease is by developing resistant varieties. The success of any breeding programme depends upon the availability of well characterised genetic resources. In this context, the current study was formulated for characterisation of exotic germplasm and identifying genetic stock of cocoa for Phytophthora pod rot resistance. Morphological characterization of 30 genotypes were carried out by recording ten qualitative and 23 quantitative characters governing leaf, flower, pod and bean. High variability was observed for most of the characters except petal colour and number of ridges and furrows. The germplasm when characterized based on biochemical parameters such as fat, polyphenols and mineral content (Na, K and Ca) also expressed wide variability. It is essential to quantify the diversity available among genotypes in order to design an effective breeding programme. Hence, cluster analysis was carried out by D2 statistics and principal component analysis. Among all the qualitative clusters, cluster III was the biggest with eight members. Cluster analysis of quantitative characters showed that most of the genotypes were placed separately in distinct cluster due to wide variability available in the germplasm. Cluster analysis of biochemical characters also exhibited wide variability which is evident from the fact that it formed 15 clusters even at 25 per cent similarity. Correlation studies and path analysis were employed to know the nature and relationships among the yield attributing characters. Here, it was found that wet bean weight (g) showed positive correlation with pod weight (g), furrow thickness (cm), pod length (cm), pod breadth (cm), weight of the bean (g) and number of beans per pod. Results of path analysis revealed that total wet bean weight (g) was directly influenced by pod thickness (cm), number of beans per pod, single dry bean weight (g) and wet bean weight (g). Since, quantitative and qualitative descriptors serve as an effective tool to discriminate among the genotypes, a evaluation data was constructed for all the genotypes considering distinct characters governing them. The non-pricking and pricking methods of pod inoculation with pure culture of pathogen were employed to know the disease resistance reaction exhibited by different genotypes. In the non-pricking method, five genotypes (ICS 41, SIAL 339, PNG 250, PNG 336 and IMC 20) with zero per cent infection and 14 genotypes (CRU 12, MO 109, GDL 7, GU 261/P, NA 149, PA 156, LX 43, POUND 4/B, JA 10/12, DOM 14, ICS 75, DOM 25, POUND 18 and POUND 16/A) with infection less than 15 per cent were grouped under highly resistant category. However, these genotypes did not show same disease resistance reaction in pricking method which indicated that the resistance was influenced by certain morphological characters apart from the internal resistance and the significance of those morphological characters were lost when pods were pricked. Binomial logistic regression revealed that different phenes like ridge thickness, polyphenol content and calcium content were positively contributing to disease resistance. Whereas, phenes like pod rugosity, pod basal constriction and pod length were negatively correlated with disease resistance. If these phenes are considered for selection, ample increase in the level of resistance will be noticed in the resultant population. Genetic stock was developed considering disease resistance and yield. As opined by many scientists “Disease resistance is a double-edged sword”. The phytotoxin developed in plants against pathogen is not only toxic to the pathogen but also to the plants resulting in yield reduction. Here also same trend was noticed and majority of the genotypes which expressed high resistance were low yielders. The accessions manifested high resistance can be used for further breeding programme.Item Characterization of selected accessions of cassava germplasm using morphological and molecular markers(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2017) Anjali sabu, C; Asha, K ICassava (Manihot esculenta Crantz), a perennial shrub, is an important crop in many parts of the tropics.This research work attempts morphological and molecular characterization of 27 cassava germplasm collected from Southern India. In the present study27 accessions of cassava maintained in the field genebank of ICAR- Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram were characterized based on 20 qualitative and 10 quantitative traits including the major yield components. There were no duplicate accessions identified based on morphological classification and it can be maintained as core collection. The genetic diversity on molecular basis was evaluated using 10 SSR primers. Molecular markers are proved to be valuable tools in the characterization and evaluation of genetic diversity within and between species and population. All the SSR primers in the study showed the polymorphism. The SSR primers on an average produced 9 polymorphic alleles with mean observed hetrozygosity and values of Polymorphism Information Content (PIC) 0.8293 and 0.8091 respectively. The value of heterozygosity here ranged from 0.2975 (SSRY 148) to 0.8293 (SSRY 9). The PIC value ranged from 0.2533 (SSRY 148) to 0.8091 (SSRY 9). The hetrozigosity and average PIC content observed in SSRY 9. Clustering based on morphological descriptors and molecular markers was done. In morphological clustering, Cluster-I consists of 7 accessions was further subdivided into two sub clusters I A and I B. Cluster-I A consisted of four accessions while Cluster-I Bof three accessions. The bigger cluster Cluster-II consisting of 20 accessions was found to have two subgroups namely II A with 12 accessions and II B with 8 accessions. Clustering based on SSR marker analysis grouped the genotypes into 2 Clusters. Cluster-I contain 6 accessions was further sub grouped into I A and I B with 3 accessions each. Cluster II with 21 accessions was found to have two subgroups II A with 13accessions and II B with 8 accessions. By comparing the morphological and molecular clusters, In Cluster II of each dendrogram have 6 similar accessions of cassava (TCR-5, TCR-10,TCR-15,TCR- 45,TCR-79,TCR-69,). Clustering and Principal Componant Analysis of the data validated the variation among the cassava accessions. In PCA of morphological characters the percentage variation obtained in PC component 1 (54.22). Mantel’s test proves that there is no correlation between the morphological and molecular data. The present results indicated that the primers selected for the present study will be useful for future genetic variability studies and would provide breeders with a genetic base for selection of diverse parents for crop improvement programmes in cassava.Item Response of selected okra [Abelmoschus esculentus (L.) Moench] cultivars to root knot nematode meloidogyne incognita (Kofoid and White)(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2017) Chandini, S M; Susannamma Kurien