Browsing by Author "Asna, A C"

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    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; Jiji Joseph
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    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.
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    Performance analysis of selected accessions of cocoa (Theobroma cacao L)
    (Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2013) Asna, A C; 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.