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2013 - 20182
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Subject: Plant Breeding × Author: Asna, A C × End date: 2018 × Start date: 2013 ×
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    ThesisItemOpen Access
    Characterization and distant hybridization for biotic stress tolerance in bitter gourd (Momordica charantia L.)
    (Department of Plant Breeding and Genetics College of Horticulture, Vellanikkara, 2018) Asna, A C; KAU; Jiji, Joseph
    Bitter gourd (Momordica charantia L.) is one of the important cucurbitaceous vegetable valued for its nutritional and medicinal properties. Bitter gourd has been in use for centuries in the traditional system of medicine of several countries like India, China, Africa, and Latin America. Even though, cultivated bitter gourd (M. charantia var. charantia) is highly vulnerable to most of the pests and diseases, its wild/semi-domesticated type (M. charantia var. muricata) is endowed with resistance/tolerance to some of the common pests and diseases of cucurbits. In bitter gourd, the major disease prevalent in south India is powdery mildew caused by fungus, Erisiphe cichoracearum. The disease severity even goes up to 80 per cent during December – January. The identification of resistance sources to major pests and diseases is essential for developing resistant cultivars. Attempts to develop disease resistant cultivars in bitter gourd by earlier workers have not found much success. The present study was taken up in this background at COH, Vellanikkara during 2014-18 to characterize and screen the selected accessions of wild/semi domesticated bitter gourd (M. charantia var. muricata) for powdery mildew resistance and to assess the possibility of transferring this tolerance/resistance to commercial varieties. Fifty accessions of wild/ semi domesticated bitter gourd and three check varieties viz., Preethi, Priyanka and Pusa Purvi formed the material for the study. These accessions were subjected to morphological and biochemical evaluation. The morphological evaluation based on 35 qualitative and 28 quantitative characters was done using the descriptor developed by NBPGR (2001). Vitamin C, iron, fibre content and total antioxidant capacity were estimated following standard procedures for biochemical characterization. Clustering based on quantitative characters was done following agglomerative hierarchical clustering method. Wide variability was observed among the accessions for all the qualitative traits except primary leaf shape and margin, stem pubescence, stem shape, leaf margin, leaf shape, fruit ribs and blossom end shape of fruit. Variation expressed by the accessions in terms of both fruit and seed quantitative traits was also high. Among the wild genotypes, IC 467681 was having the highest fruit weight, fruit length and fruit width. However, its yield was only 969.49 g/plant. The highest yield was observed in the cultivated types followed by AC-16/1 (1493.88 g). The cluster analysis based on quantitative characters resulted in four clusters at 90 per cent similarity level. Clustering clearly separated wild genotypes from cultivated ones by placing Preethi and Priyanka in cluster III and IV respectively. High heritability coupled with high genetic gain was observed (>20%) for number of fruits per plant, yield per plant, fruit length, number of seeds per fruit and 100 seed weight. The biochemical characters viz., Vitamin C, iron, fibre content and total antioxidant capacity ranged from 76.53 to 125.67 mg/100 g; 1.48 to 3.31 mg/100g; 12.17 to 30.44 per cent and 41.88 to 92.01 mg AAE/g respectively. Based on organoleptic evaluation, the maximum score for overall acceptability was obtained for Priyanka followed by Preethi and AC-16/1. All the bitter gourd accessions were screened under natural field conditions during 2016 and 2017 for their reaction to powdery mildew and mosaic diseases. Based on per cent disease severity of the accessions during two consecutive crop seasons, five accessions viz., IC 213312, AC-16/1, AC-16/4, AC-16/9, and AC-16/21, which were resistant to both diseases were identified and crossed with susceptible check varieties in Line × Tester design. All the fifteen hybrids along with five parents were evaluated for powdery mildew tolerance/resistance and yield characters. Nine crosses were immune to powdery mildew disease. The better performing wild genotypes with respect to yield, fruit weight, organoleptic score and resistance, viz., AC-16/1, AC-16/16, IC 467681 and JJNS-15/65, should be further tested in large scale yield trials and recommended for commercial cultivation especially for homestead farming.
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    ThesisItemOpen Access
    Performance analysis of selected accessions of cocoa (Theobroma cacao L)
    (Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2013) Asna, A C; KAU; Presannakumari, K T
    The spreading cultivation of cocoa as an intercrop in states like Kerala, Tamil Nadu, Andhra Pradesh and Karnataka necessitated the development of high yielding hybrids with pest and disease resistance and adaptability to various agro climatic zones. The success of any hybridization programme particularly in perennials depends on the proper selection of parental lines having genetic divergence. The present study entitled “Performance analysis of selected accessions of cocoa (Theobroma cacao L.)” was taken up in this background at COH, Vellanikkara during 2011-13 to evaluate and characterize the selected cocoa accessions and to assess the genetic divergence among them. Fifty accessions of cocoa comprising of both exotic and indigenous ones which are in the full bearing stage and maintained at Cocoa Research Centre, Vellanikkara formed the material for the study. These accessions were subjected to morphological and biochemical evaluation. The morphological evaluation based on 13 qualitative and 25 quantitative characters was done using the descriptor developed by Bekele and Butler (2000). Fat and total polyphenol contents were estimated following standard procedures for biochemical characterization. The clustering of the accessions based on these characters was done by unweighted pair group method (Sneath & Sokal, 1973) and the genetic divergence was estimated by D2 statistics developed by Mahalonobis (1936). Wide variability was observed among the accessions for all the qualitative traits except colour of staminodes and hardiness of husk. Variations expressed by the accessions in terms of both floral and pod quantitative traits were also high. Among the exotic accessions, COCA 3370-3 was having the highest pod weight, pod length, pod breadth, ridge thickness and furrow thickness. However, its wet bean weight accounted only for 14.79 percent of the pod weight. Among the indigenous types, Konni local 2 was the best performer for these traits. The characters of economic interest viz., pod weight, number of beans/pod, dry weight of peeled bean, percentage of flat beans/pod and pod index ranged from 318.67g to 1268.33g, 22.93 to 49.27, 0.58g to 1.72g, 0.00 to 12.60 percent and 12 to 49 respectively among the exotic accessions. The corresponding traits in the case of indigenous accessions ranged from 416.67g to 719.33g, 31.60 to 46.27, 0.93g to 1.52g, 0.75 to 7.86 percent and 17 to 34 respectively. Among the accessions evaluated R (10) (MEX) was found to be a desirable one with low pod index value (12) and flat bean content/pod (0.81%) coupled with high number of beans/pod (49.20) and dry weight of peeled bean (1.68g). This is followed by EET 400 having a pod index of 15. The exotic accessions Criollo, KER 9 and CLM 90 failed to satisfy the international standard for dry weight of peeled bean viz., 0.8g or more. The fat content ranged from 40 percent to 60 percent and total polyphenol content from 2.25 percent to 9.09 percent. The cluster analysis based on qualitative and quantitative characters resulted in nine and seven clusters respectively for exotic accessions and five and three clusters respectively for indigenous ones. The accessions belonging to same qualitative cluster were found to fall in different quantitative clusters indicating that even though they are similar at qualitative level they are different at quantitative level. With respect to biochemical characters majority of accessions were remaining as independent units even at one percent similarity level and hence could not be clustered. Among the exotic types, the maximum genetic divergence was observed among the accessions falling in quantitative cluster I and V as indicated by the highest inter cluster distance (33763.40). In the case of indigenous ones maximum divergence was found among the accessions falling in cluster I and II (148447.4). Mealy bug and tea mosquito bug were the major pests and black pod was the major disease affecting the pods resulting in yield loss. Besides, rodents like rats and squirrels also caused damage to the pods. Among the accessions evaluated, COCA 3370-3 having high husk thickness was found to be tolerant to the major pests and diseases affecting the pods and can serve as donor parent in resistance breeding programme. A statistical key was developed using key qualitative and quantitative characters which can serve as a preliminary tool for predicting the performance of the accessions.