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ThesisItem Open Access Genetics of shattering resistance in rice (Oryza sativa L.)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Akhil, K P; KAU; Biju, SRice is the staple food crop of Kerala. Among the plethora of rice varieties available Jyothi is by far the most popular in the state owing to its consumer preference. Easy seed shattering leads to significant loss in Jyothi which can be overcome by transferring shattering resistance to it. Screening of genotypes for shattering resistance identified donors like Athira and Triveni with good combining ability. The present experiment was thus envisaged to transfer shattering resistance to Jyothi from the donors and to study the nature of inheritance of seed shattering trait using six parameter model of generation mean analysis. Observations were recorded in the two crosses viz., Jyothi x Aathira and Jyothi x Triveni for eleven quantitative characters viz. days to 50 per cent flowering, plant height, tillers per plant, panicles per plant, panicle length, spikelets per panicle, seeds per panicle, days to maturity, test weight, grain yield per plant and shattering per cent in six generation (P1, P2, F1, F2, B1 and B2) obtained from the two crosses. Panicle per plant, test weight, grain yield per plant and shattering per cent recorded significant heterosis in the desirable direction in both the crosses. Mean effect (m) was significant and positive for all the characters studied in both the crosses. The additive component (d) was significant and positive for days to 50 per cent flowering, tillers per plant, panicles per plant, days to maturity, grain yield per plant and shattering per cent in the cross Jyothi x Triveni while the other characters recorded significant and negative additive gene effect. The characters tillers per plant, test weight and shattering per cent showed significant positive additive gene effect in the cross Jyothi x Aathira and rest of the characters showed significant and negative additive component. Dominance gene effect was observed to be significant and negative for most of the characters studied in both the crosses. Non-allelic interactions were observed to be significant in most of the characters except days to 50 per cent flowering, tillers per plant, days to maturity and shattering per cent in the cross Jyothi x Aathira. The epistatic interaction model of generation mean analysis was found adequate for obtaining gene actions for all the characters. Among the three type of interactions dominance x dominance interaction was found to be more important for all the characters. Additive x additive and additive x dominance gene interactions were found to be equally important for most of the characters studied in both the crosses. Dominance gene effect was observed controlling the genetic variance in most of the traits studied. Presence of additive and non-additive along with epistatic interaction revealed the complex nature of inheritance of the characters. Predominant dominant gene effect along with duplicate epistasis limits the scope of direct selection. In the F2 populations characters showed high heritability in both the populations studied. Plant height, panicle length and days to maturity were found to have low genetic advance. Plant height recorded moderate genetic advance, whereas, other characters exhibited high genetic advance in F2 population derived from the cross Jyothi x Triveni. Days to maturity showed low genetic advance, days to 50 per cent flowering and panicle length recorded moderate genetic advance and other characters recorded high genetic advance in F2 population derived from the cross Jyothi x Aathira. As shattering resistance is governed predominantly by additive gene effects selection in the early segregating generations will be highly rewarding. The selected lines may be advanced to further generations to identify lines with high yield coupled with shattering resistance and can be forwarded to develop high yielding varieties with low shattering or bi-parental mating among the selected lines may be undertaken to recover superior recombinants with high yield and shattering resistance.ThesisItem Open Access Development of doubled haploids for iron toxicity tolerance in rice (Oryza sativa L.)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Chakravarthi Mari, Bastian; KAU; Dijee, BastianRice is the staple food crop of the people of Kerala. The production of rice in Kerala is impeded by many biotic and abiotic stresses. Iron toxicity is one of the major abiotic stresses of acidic soils in Kerala. The present study “Development of doubled haploids for iron toxicity tolerance in rice (Oryza sativa L.)” was taken up with the objective of developing doubled haploids with tolerance to iron toxicity through in vitro anther culture. Doubled haploids being homozygous stable lines, can be used both as immortal populations for QTL mapping as well as varieties, if suitable agronomic traits are present in them. Therefore, this study was taken up which comprised of three experiments. In experiment I, two tolerant genotypes (Swetha and Mangala Mahsuri) and two susceptible genotypes (Cul-90-03 and Cul 8709) were crossed with Tulasi. In the second experiment the parents along with their hybrids were evaluated for biometric characters and yield. The hybrids obtained from the crosses were significantly different for all the characters observed. Panicles per plant and grain yield per plant recorded highly significant and positive relative heterosis and heterobeltiosis. The anthers from the F1s produced in the previous experiment were used for anther culture studies in the third experiment. Sterilisation with various sterilants like 70 % ethanol, 0.1 % mercuric chloride, 5.25% sodium hypochlorite and their combinations were done. Explant sterilisation with 5.25% sodium hypochlorite for 5 to 20 minutes was effective in controlling contamination in the in vitro cultures. Study to know the best number of days of cold pre-treatment at 10oC was done (0, 3, 6, 9, 12, 15 days). Cold pre-treatment of anthers at 10oC for 9 days was found to be optimum for most of the genotypes studied. Two different media viz., N6 and B5 were tried with different combinations of 2,4 - D and Kn. N6 media responded better than B5 media for callus induction in all the growth hormone combinations. The effect of carbon source on callusing was studied using maltose and sucrose at various levels (30,40,50 mg/L) and it was found that maltose at 30g/L gave the best callus induction (7.95%). Among the auxins used in the present study,2,4-D was found to be better than NAA for callus induction while among cytokinins, Kinetin responded better than BAP for callus induction. The growth hormone combination 2,4- D (2mg/L) + Kn (0.5mg/L) was adjudged the best for callus induction. Additives like silver nitrate (AgNO3), casein hydrolysate (CH), yeast extract (YE), proline and activated charcoal were added to the basal media to improve callusing. when AgNO3 is applied from 0 to 1ml with 0.1 ml gradation, 0.5-0.6ml of 0.1N AgNO3 was found to be better in callus induction as well as the days to callus induction was reduced at these concentrations. 250 – 500 mg/L of CH and 250mg/L proline were found to induce significant response for callusing while activated charcoal and yeast extract did not have any considerable effect on callus induction. Hybrid H1 recorded good callus response when maltose at three levels was tried in the media (30, 40, 50g/L) whereas hybrid H2 gave uniform response at all the levels of maltose. There was significant variation among the genotypes in their response to all the factors studied. The best responses were as follows: - H1(Swetha x Tulasi) - N6+2,4-D (2mg/L) + Kn (0.5mg/L) + 30g/L maltose +0.5ml (0.1 N AgNO3) + 250mg/L proline + 250mg/L CH +2.5g/L gelrite gellan gum. H2(Mangala Mahsuri x Tulasi) - N6+2,4-D (2mg/L) +Kn (0.5mg/L) + 30g/L maltose +0.5ml (0.1N AgNO3) +250mg/L proline+250mg/L CH +2.5g/L gelrite gellan gum. H3(Cul-90-03 x Tulasi) - N6+2,4-D (2mg/L) +Kn (0.5mg/L) + 30g/L maltose + 0.5ml (AgNO3) + 250mg/L proline + 250mg/L CH + 2.5g/L gelrite gellan gum. H4(Cul 8709 x Tulasi)- B5 + 2,4-D (2mg/L) + Kn (0.5mg/L) + 30g/L maltose + 0.5ml (0.1N AgNO3) + 250mg/L proline + 250mg/L CH + 2.5g/L gelrite gellan gum. The calli obtained from the different genotypes were plated on two different callus regeneration media R1 (MS+ NAA(1mg/L) + Kn (2mg/L) + IAA (0.5mg/L) + CW (5%)) and R2 (MS+NAA (0.25mg/L) + BAP (0.75mg/L) + Kn(0.25mg/L)). There was no response in R1 media. Callus regenerated into plantlets in R2 but all the plantlets obtained were albinos leading to mortality and hence plantlet hardening and field planting could not be undertaken.ThesisItem Open Access Preliminary evaluation of double cross hybrids for yield and vascular streak dieback (VSD) disease resistance in cocoa (Theobroma cacao L.)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Alfiya, A R.; KAU; Minimol, J SCocoa is highly influenced by the climate change and growing environment, necessitating a long term and dynamic breeding programme. Even though the breeding programmes primarily focus on the development of high yielding varieties, outbreak of new pests and pathogens shift the priority to the development of resistant varieties. Vascular Streak Dieback disease (VSD) caused by Ceratobasidium theobromae (Samuels et al., 2012), pose a great threat to cocoa crop, causing complete defoliation and eventual death (Abraham et al., 2002). Even the high volume spray of chemicals was ineffective in disease control (Prior, 2007), and the only way to tackle it is to breed resistant varieties. Resistance breeding may result in yield reduction (Xu et al., 2017) however, breeding for double cross hybrids can overcome this situation (Gallais and Guy, 1971). Average yield superiority of the double cross hybrids over the F1 hybrids has been shown by many scientists (Sriani et al., 2003; Ghanwat et al., 2016). Twenty double cross hybrids, bred for vascular streak dieback disease and planted during 2017, were used for the present study. Morphological characterization of the hybrids was carried out based on the quantitative and qualitative characters. Thirteen pod characters, twelve floral characters, six bean characters and flush colour of the leaves were studied. Except colour of the petal and number of the ridges and furrows, all other characters have expressed high variability among the double cross hybrids. The double cross hybrids have exhibited significant difference for fat and polyphenol content. All the twenty double cross hybrids were screened and scored for the VSD resistance in the field condition, using the score chart (Abraham et al., 2000). Based on the disease intensity, they were classified into eleven resistant and nine partially resistant.ThesisItem Open Access Varietal evaluation and development of hybrids in Phalaenopsis orchids(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2020) Roshin Mariam, George.; KAU; Beena, ThomasThe research programme entitled “Varietal evaluation and development of hybrids in Phalaenopsis orchids” was undertaken in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, during 2018-2020. The objective of the study was to assess the genetic variability of Phalaenopsis orchids and to improve them through intervarietal hybridization. The first experiment was varietal evaluation wherein ten genotypes of Phalaenopsis, King Car Purple Queen, Lianher Happy Song, Fullers Rabbit, Lianher Orange, Fullers, Taisuco Fire Bird x King Hisang Rose, Reyoung Gold, Jiuhbao Venus, Wang Lin Rose and Young Home Golden having good market value and cut flower qualities were evaluated in the green house using completely randomized design. The analysis of variance revealed that significant difference exists among the parental genotypes with respect to the majority of biometric characters studied. Vegetative characters such as leaf area, plant height, number of leaves and leaf width exhibited the highest estimates of variance at both genotypic and phenotypic levels. Among the floral traits, length of inflorescence, number of flowers per inflorescence, vase life, internodal length of the peduncle and days to first flower opening from inflorescence emergence showed the highest genotypic and phenotypic variances. Floral characters like length of inflorescence, flower longevity on the plant, days to first flower opening from inflorescence emergence, length of flower, width of the flower and internodal length of peduncle as well as vegetative characters like plant height, leaf width and leaf area showed high heritability. Many of the characters exhibited high genetic advance (> 20%); the highest value was observed for length of the inflorescence followed by leaf area. High heritability (>70%) combined with high genetic advance (>20%) was exhibited by majority of the characters under study like days to first flower opening from inflorescence emergence, flower longevity on the plant and vase life. The genotypic, phenotypic and environmental correlations of the ten parental genotypes were studied for eleven biometric characters. High positive correlation at genotypic and phenotypic levels was observed between most of the vegetative and floral characters studied. Highly significant positive correlations were exhibited by length of the flower with number of flowers per inflorescence, length of inflorescence with number of inflorescence and number of flowers per inflorescence with vase life. The second experiment was hybridization and compatibility analysis. Intercrossing in all possible combinations involving the three best parental genotypes of Phalaenopsis selected based on inflorescence characters was done. Jiuhbao Venus, Young Home Golden and Lianher Orange were selected for intercrossing. All nine possible combinations including three selfs, three crosses and three reciprocals were attempted. Out of the nine crosses, four combinations succeeded in producing harvestable green capsules. They are Jiuhbao Venus x Young Home Golden, Jiuhbao Venus x Lianher Orange, Young Home Golden x Jiuhbao Venus and Young Home Golden x Lianher Orange. The highest strength of incompatibility was exhibited by Lianher Orange. Germination in vitro was observed for the four combinations from which the green capsules were successfully harvested. These hybrid combinations can be utilized for further crop improvement programmes.ThesisItem Open Access Genetic variability studies in grain cowpea (Vigna unguiculata (L.) Walp.)(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2020) Darshana, A S.; KAU; Bindu, M RThe study entitled “Genetic variability studies in grain cowpea (Vigna unguiculata (L.) Walp.) was carried out at Farming Systems Research station, Sadanandapuram during December, 2019 – March, 2020 with the objective to evaluate and select shade tolerant grain cowpea genotypes suited to the coconut based homesteads. The 33 grain cowpea genotypes collected from research stations under KAU, AICRP centre and agricultural universities of different states were evaluated in coconut based homestead garden where coconuts are of age 30 – 40 years, in randomized block design replicated thrice. The seeds were sown on raised beds of (3 х 1.5) m2 size at a spacing of 30 cm х 15 cm and cultural operations and plant protection measures were adopted as per the “Package of Practices Recommendations: Crops 2016” of Kerala Agricultural University. The average light intensity in the experimental field recorded was 0.719 W/m2 resulting in shade of 33.49 per cent. The genotypes were evaluated for biometric and physiological characters associated with shade tolerance and quality character of seed. The genotypes showed significant differences for all the characters studied. Genetic parameter analysis was performed for twelve characters and for all the characters PCV values were higher than GCV values indicating the influence of environment. The phenotypic and genotypic coefficients of variation were maximum for seed yield per plant and minimum for protein content. Heritability was high for all the twelve characters and genetic gain was high for all the characters except days to 50% flowering and protein content. The correlation studies revealed positive correlation of the characters days to 50% flowering, number of pods per plant, number of seeds per pod, crop duration, harvest index, LAD at flowering, CGR at flowering and protein content with seed yield. The path analysis provides information on contribution of traits by partitioning the total correlation into direct and indirect effects. Path analysis of the eight characters showing significant correlation with seed yield revealed high positive direct effect of the characters number of pods per plant and harvest index on seed yield. High indirect effect on seed yield was observed for CGR at flowering through number of pods per plant. 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 33 genotypes into nine clusters. Cluster II with 10 genotypes was the largest followed by cluster I and cluster V (8 genotypes each), cluster III (2 genotypes) and clusters IV, VI, VII, VIII, IX which were solitary clusters. Highest intra cluster distance was recorded among the genotypes of cluster V and lowest in cluster III whereas highest inter cluster distance was observed between the genotypes of the clusters III and IX followed by clusters VI and IX. The present study revealed that the variety Sreya recorded highest seed yield under partially shaded condition. The genotypes CHESCP-03, CHESCP-17 and CHESCP-32 are medium in duration with shade tolerance and higher yield, hence suited to the coconut based homesteads. Among the early duration types, Subhra recorded the highest yield. Genotypes CHESCP-19 and KYLMVU-6 recorded yield on par with the shade tolerant genotypes CHESCP-03, CHESCP-17 and CHESCP-32. Subhra and the late duration varieties Sreya, CHESCP-19 and KYLMVU-6 recorded low values for shade tolerant parameters and there is scope for improving the yield by hybridization with shade tolerant varieties. Subhra and CHESCP-21 were found to be superior for protein content. As quality of a pulse variety is determined by the protein content, these genotypes can be used as parents in quality improvement programmes. The superior genotypes identified in the study can be recommended for cultivation and future breeding programs.ThesisItem Open Access Genetic analysis in green gram (Vigna radiata (L.) Wilczek)(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2020) Reshma S, Nair; Arya, KThe study entitled “Genetic analysis in green gram (Vigna radiata (L.) Wilczek)” was conducted at the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 2018-2020. The study was carried out to assess the existing genetic variability and performance of different genotypes of green gram under open and partially shaded conditions and to identify the best genotype in terms of yield and protein content. Two simultaneous field experiments under open and partially shaded conditions were conducted during 2019-2020. Intercropping is done in coconut garden with an average of 57 per cent shade in order to provide required partial shade. Thirty green gram genotypes procured from NBPGR, New Delhi and nearby State Agricultural Universities were assessed in a randomized block design, replicated thrice. The seeds were dibbled on raised beds in the field at a spacing of 30 cm x 15cm and each genotype was considered as individual treatment. Very few pests and pathogen attack was observed in the field for which control measures were taken up. The thirty genotypes were evaluated for eighteen characters and their mean values were recorded. Analysis of variance, estimation of genetic parameters such as genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability and genetic advance, correlation analysis and path coefficient analysis were carried out. A pooled analysis was also conducted to compare the performance of genotypes for each character in open and partially shaded conditions. Variability analysis revealed the existence of a considerable amount of variability for yield per plant, plant height, number of pods per plant, harvest index and days to maturity under both open and partially shaded conditions, whereas number of secondary branches and chlorophyll content showed narrow range of variation. Emergence percentage was more under partial shade than open condition. Likewise, plant height, specific leaf area and chlorophyll content exhibited an increase under partial shade compared to those under open condition. Estimates of phenotypic coefficient of variation were higher than corresponding genotypic coefficient of variation for all the characters studied. The highest GCV was recorded for yield per plant under both open and partially shaded conditions, respectively followed by number of primary branches per plant and number of pods per plant. High heritability was recorded for most of the characters studied under both growing conditions. High heritability coupled with high genetic advance as per cent of mean was recorded for yield per plant, number of primary branches, number of pods per plant and 100 seed weight under both conditions, whereas under open condition, two more characters such as number of secondary branches per plant and chlorophyll content also showed high heritability with high genetic gain. The character yield per plant was found to be highly significant and positively correlated with harvest index, number of pods per plant, number of secondary branches per plant and pod length both at genotypic and phenotypic levels under open and partially shaded conditions indicating their importance in yield enhancement. Path analysis was carried out using yield per plant as the dependent variable and other characters as independent variables. The study revealed that, harvest index and number of pods per plant had high positive direct effect on seed yield per plant, followed by days to maturity, pod length and number of primary branches per plant. High indirect effect was recorded for number of pods per plant on yield per plant through harvest index. The results of the present study revealed the presence of ample variability among the thirty green gram genotypes under open and partially shaded conditions. The genotype BGS 9 was found to be superior in yield performance under open condition which was on par with the genotype IC 282124. Under partially shaded condition, the genotype K7 recorded the highest yield and was on par with the genotypes BGS 9 and IC 282124. When protein content was assessed, maximum value was recorded for genotype K10 under open condition and genotype K13 under partially shaded condition. The superior genotypes identified in the present study can be utilized as such after further trials or as parents for crop improvement programmes to develop superior varieties.ThesisItem Open Access Genetic analysis in fodder rice bean (Vigna umbellata (Thunb.) for yield and quality(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2020) Bhoomika, B K; KAU; Mareen, AbrahamRice bean is an underutilized fodder legume, belonging to family Fabaceae, having chromosome number 2n=22. It is emerging as a potential nutritious high yielding animal fodder with no major pest and disease incidence and demands no fertilizer and little special care during growth. In India and Nepal it is mainly grown in two seasons February and March for harvest during summer and in July and August for harvest during December. It can be grown as sole crop or inter crop with maize and sorghum. The present investigation „Genetic analysis in fodder rice bean (Vigna umbellata (Thunb.) for yield and quality‟ was conducted at Department of Plant Breeding and Genetics, College of Agriculture, Vellayani. 30 genotypes of rice bean collected from NBPGR were evaluated in Randomized Block Design with three replications. The crop was harvested at 50% flowering stage. Observations were recorded for various qualitative and quantitative characters, viz. days to first flowering, days to 50% flowering, plant height, number of branches, number of leaves, leaf fresh weight, stem fresh weight, green fodder yield, leaf dry weight, stem dry weight, dry fodder yield, leaf area index, leaf stem ratio, production efficiency, crude protein, crude fiber and dry matter production. Various statistical tools such as analysis of variance, genotypic coefficient of variation (PCV), phenotypic coefficient of variation (GCV), heritability, genetic advance, correlation studies, path analysis and cluster analysis were carried out to find out extent of variation present in existing genotypes. Analysis of variance was found to be significant for all the characters except for the character days to 50% flowering. This reveals the presence of variability among the genotypes and hence selection can be effective in the population. The genotype IC341991 recorded maximum leaf fresh weight (17.41 t ha-1), stem fresh weight (21.87 t ha-1), green fodder yield (35.49 t ha-1), leaf dry weight (2.5 t ha-1), stem dry weight (3.82 t ha-1) and dry fodder yield (6.46 t ha-1), which was on par with the genotypes IC341986 and IC521350. Minimum green fodder yield was recorded by the genotypes EC98452 (22.32 t ha-1) IC341998 (23.25 t ha-1) EC16136 (24.12 t ha-1). Maximum Crude protein content was recorded for the genotypes IC521119 (21.0%), IC521152 (20.27%) and IC521115 (19.74%) while minimum crude protein content was reported for the genotype IC18553 (13.30%). Crude fibre content was found to be high for the genotype IC469192 (6.7%) and lowest crude fibre content was recorded for the genotype EC98452 (2.8%). The parameters of genetic variability such as genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV). Heritability (H2) and Genetic Advance (GA) were carried out to find genetic variability present in the genotypes. All PCV values were highest then the GCV values, indicating least influence of environment on the expression of characters. Maximum PCV and GCV were observed for the characters crude fibre and dry fodder yield. High heritability coupled with high genetic advance was reported for the characters dry matter production, crude fibre, leaf area index, crude protein and dry fodder yield. High heritability and genetic advance indicates presence of additive gene action and hence selection of these characters will be rewarding. Correlation studies gives information about degree and magnitude of relationship between two or more variables. Green fodder yield showed significant positive correlation with number of leaves, stem fresh weight, production efficiency, stem dry weight, leaf area index, dry fodder yield, leaf fresh weight, dry matter production, number of branches, plant height, leaf dry weight, crude fibre and leaf stem ratio. Path analysis is a multiple regression statistical analysis which partitions the correlation coefficients into measures of direct and indirect effect. path analysis revealed that characters production efficiency, leaf dry weight, plant height, number of leaves, crude protein, leaf fresh weight, leaf stem ratio and number branches showed direct positive effect on green fodder yield. Cluster analysis was carried out to know the extent of genetic diversity present in the population. Based on D2 statistics 30 genotypes of rice bean were grouped into 5 clusters following Tocher‟s method luster I being the largest cluster contains 12 genotypes followed by cluster III (10 genotypes), cluster IV (4 genotypes), cluster III (3 genotypes) and cluster V (1 genotype). Highest intra cluster distance was observed in the genotypes falling under the cluster III followed by IV and II. Maximum inter cluster distance was observed in the genotypes falling under the cluster III and V, followed by II and III and I and V. Genotypes should be selected from the clusters which shows highest divergence for the success of breeding program. The study revealed presence of ample amount of variability among the genotypes for all the characters studied. The genotype IC341991was found to be superior in terms of yield and yield attributing characters followed by genotypes IC341986, IC521350 and IC521134. These superior genotypes can be forwarded for further trials for variety development or can be used as parents for future breeding work.ThesisItem Open Access Characterization of exotic germplasm of rice (Oryza sativa L.) for yield and quality attributes(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Maqsoodullah; KAU; Jiji, JosephGenetic diversity in rice, one of the most ancient and major food crop of the world, far exceeds that in any other crop. The present study on “Characterization of exotic germplasm of rice (Oryza sativa L.) for yield and quality attributes” was done in the Department of Plant Breeding and Genetics, College of Horticulture, and at the experimental farm of NBPGR Regional station, Thrissur, during June 2019 to October 2019. Hundred exotic accessions of rice received from IRRI, Philippines were evaluated along with five checks varieties viz., PTB 39 (Jyothi), Jaya, Thulasi, PTB 60 (Vaisakh) and Manurathna. The experiment was set in augmented block design with 5 blocks; each block comprising of 20 exotic accessions and five check varieties. Each entry was planted in plots of 5m2 at a spacing of 15 x 20 cm2. Out of hundred accessions, eighty-nine germinated and were evaluated for qualitative and quantitative traits at appropriate stages as per DUS descriptor (2006). Out of the 25 qualitative traits observed, eight each were monomorphic and dimorphic. The traits flag leaf attitude, lemma and palea colour, colour of apiculus, distribution of awns, panicle attitude of main axis, panicle exsertion, and pericarp colour were found to be trimorphic. Colour of awns and caryopsis shape had four classes. Qualitative traits were less affected by the environment and they can be used as robust morphological markers for identifying genotypes. Twenty-two accessions were identified as superior with erect leaf, erect flag leaf, erect and strong culm and well exserted panicle. Based on qualitative characters accessions grouped into 12 clusters. Thirty-five accessions belonged to the first cluster. Cluster 3 comprised 25 accessions, Cluster 9 and 11 consisted of 11 accessions each. Second cluster included two accessions, while cluster 10 had three accessions. Other six clusters were composed of single accessions. Observation on quantitative characters showed that seventeen accessions were having low height than the check varieties. Thirty-six accessions were having longer ligule, while, fifteen accessions were having longer leaf and accession EC 204863 had broader leaves. Thirty-three accessions were early to flower and 34 accessions were early to mature. Accessions EC 207747, EC 204863, EC 205042 and EC 205128 had high number of tillers. Accessions EC 207747, EC 204863, EC 205070 and EC 415401 had high number of productive tillers per plant. Accessions EC 204847, EC 205001, EC 205223, EC 205314, EC 415448 and EC 415452 had more number of spikelets. While, comparing with check varieties, eighteen accessions had longer panicles. Eight accessions had more grain number and nineteen accessions had longer grains. Majority of the accessions had grain yield on par with check varieties. Correlation studies showed that plant height had positive correlation with leaf length and width, number of total and productive tillers, panicle length and grain width. Correlation of ligule length with leaf length and grain width was negative. Leaf length was correlated with leaf width, number of total tillers and grain width. Leaf width exhibited positive association with plant height, length of leaf blade, number of total tillers, hundred seed weight, panicle length and grain width. Days to fifty per cent flowering expressed negative association with test weight. Total number of tillers was positively associated with plant height, length and breadth of leaf, number of productive tillers, panicle length and grain width, whereas, it was negatively correlated with grain length. Number of spikelets per panicle had positive correlation with grains per panicle and negative association with grain length. Positive and significant association was observed between 100 grain weight and grain yield. Dendrogram constructed using average linkage distance resulted in four clusters with majority of the accessions falling in the cluster 1. Accessions EC 207747, EC 204970, EC 204999, EC 205042, EC 205047, EC 205192, EC 2052015, EC 205223, EC 205333, EC 415392, EC 415403, EC 415407, EC 415413, EC 415420, EC415421, EC 415422, EC 415445, EC 415452 were identified as superior when quantitative and qualitative traits considered together and these exotic accessions can be used in breeding programmes after further confirmation studies.ThesisItem Open Access Assessment of genetic variability for YVM resistance in okra (abelmoschus esculentus (L.) moench)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Abdul, Basir; KAU; Sindhumole, POkra (Abelmoschus esculentus (L.) Moench) is an important vegetable crop which is widely grown in tropical, temperate and subtropical regions of the world. The present investigation on ‘Assessment of genetic variability for YVM resistance in okra (Abelmoschus esculentus (L.) Moench)’ was conducted at the Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, Thrissur during November 2019 to February 2020. The experiment was laid out in augmented design using thirty four okra accessions including two resistant check varieties (Parbhani Kranti and Varsha Uphar) and two susceptible check varieties (Salkeerthi and Pusa Sawani) collected from NBPGR and KAU. Ten plants of each accession were sown on ridges in a row with 60 cm x 45 cm spacing and the crop was managed as per package of practices recommendations of KAU (2017). Observations on five qualitative characters and fifteen quantitative characters were recorded from five randomly selected plants for each accession, as per the NBPGR descriptors. Scoring for YVM disease incidence was done as per the rating scale given by Arumugam et al. (1975). The genotypes were classified based on five qualitative characters viz., fruit colour (multimorphic), fruit pubescence and petal colour (trimorphic), petal base colour (dimorphic) and seed hairiness (monomorphic). ANOVA for fifteen quantitative characters showed significant variation for days to flowering, leaf blade length , leaf area), plant height, branches per plant, fruit length, fruit diameter, ridges per fruit, seeds per fruit, number of fruits per plant, fruit weight, fruit yield per plant, coefficient of YVM incidence and vector population on young leaves. This indicated high variability in the okra germplasm which can be utilised in breeding programmes. Phenotypic and genotypic coefficients of variation (PCV and GCV) were very high for leaf area and coefficient of YVM infection and high for five characters viz., fruit yield per plant, branches per plant, plant height, fruits per plant and ridges per fruit. In general, GCV was slightly lower than PCV for most of the traits indicating a small environmental effect in their expression. Broad sense heritability (H2) was very high in three traits (leaf area, seeds per fruit and ridges per fruit) while genetic advance as % of mean (GA) was very high in two traits (leaf area and coefficient of YVM Infection). High H2 and GA were noticed in most of the traits including number, length, diameter, weight and yield of fruits. Coefficient of YVM infection also exhibited high H2 as well as GA. This indicates that these characters can be improved to a great extent by selection. Fruit yield per plant had highly significant positive correlation with leaf area and seeds per fruit and significant positive correlation with days to first flowering, leaf blade width and plant height. Positive and highly significant correlation was observed for coefficient of YVM infection with days to first flowering, leaf area and vector population. In the high yielding YVM susceptible category, the six best okra genotypes selected were Salkeerthi, TCR- 1774, TCR-1797, TCR- 2631, TCR-2627 and TCR-2626. Salkeerthi (KAU variety) in spite of being susceptible to YVM, had the highest fruit yield per plant (294.22 g) among all the genotypes evaluated in the present study. Besides, it had superior yield components viz., fruitsper plant, fruit length, fruit diameter and fruit weight. All the other selected genotypes (collected from NBPGR) were also superior in fruit yield per plant and other major yield components. These selected NBPGR accessions may further be evaluated for confirming their superiority in yield and yield traits. Three genotypes viz., TCR- 30, Varhsa Uphar and Parbhani Kranti showed high resistance during the present study. Varhsa Uphar and Parbhani Kranti (two resistant checks) exhibited superiority in fruit yield as well as yield components viz., fruit number/plant, fruit length, fruit diameter and fruit weight. Even though a low yielder, TCR- 30 exhibited consistent high resistance to YVM disease throughout the crop period with the lowest number of white flies emphasising its resistance mechanism. Hence it can be recommended as a donor for imparting YVM resistance in breeding programmes.