Breeding for yellow vein mosaic virus (YVMV) resistance in OKRA (Abelmoschus esculentus (L.) Moench)
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Date
2020
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Department of Vegetable Science, College of Horticulture, Vellanikkara
Abstract
Okra is one of the most important vegetable crops grown in India for its tender green fruits. The cultivation of okra is constrained by various pests and diseases. Among the diseases, Yellow Vein Mosaic Disease (YVMD) is the most dreadful disease which affects both the quality of fruit and yield adversely. It is a viral disease caused by Yellow Vein Mosaic Virus (YVMV) and is transmitted by whiteflies (Bemisia tabaci). The only practical solution to this problem is development of resistant or tolerant varieties. The resistant varieties released in the past became susceptible due to the development of new strains of virus or due to the recombination in the virus strain. In this background, the present study entitled “Breeding for Yellow Vein Mosaic Virus (YVMV) resistance in okra [Abelmoschus esculentus (L.) Moench]” was undertaken with the objective of evaluating and identifying resistant varieties/lines of okra against YVMV for augmenting effective resistant breeding programme in okra. The present study was carried out at Department of Vegetable Science, College of Horticulture, Vellanikkara during the period of 2018-2020. The experimental material consisted of 34 genotypes of okra which were sown in randomized block design with two replications. Out of 34 genotypes, 30 were collected from NBPGR Regional station, Akola. Remaining genotypes included Arka Anamika and KAU varieties namely Aruna, Salkeerthi and Susthira. The genotypes were evaluated for their qualitative and quantitative characters and described based on the NBPGR Minimal Descriptor for Characterization and Evaluation of Agri-Horticultural Crops (2000). All the 34 genotypes were evaluated under natural conditions for the selection of resistant/tolerant ones. The disease reaction of genotypes to Yellow Vein Mosaic Disease (YVMD) were evaluated based on the parameters viz., percent disease incidence, percent disease severity and coefficient of infection. Based on the values of coefficient of infection, the genotypes were classified as resistant, susceptible and highly susceptible. The results revealed the presence of highly resistant to highly susceptible genotypes in the present study. Six genotypes (EC 305645, EC 305651, EC 305674, IC 13995, IC 14845 and Arka Anamika) were grouped as highly susceptible, 27 genotypes as susceptible and Susthira as highly resistant. Among the genotypes evaluated, Susthira showed resistance to YVMD at all stages of crop growth under field conditions. Resistance of Susthira was further confirmed under protected conditions using vector transmission method. Hence, Susthira can be used as a source of resistance for developing YVMD resistant/tolerant varieties. The extent of variability present in the germplasm were studied using the parameters viz., phenotypic coefficient of variation (PCV), genotypic coefficient of variation (GCV), heritability and genetic advance. High heritability and genetic advance were observed for the characters viz., plant height, internodal length, number of fruits per plant, number of seeds per fruit, crop duration, number of ridges per fruit, 100 seed weight, average fruit weight, number of harvest, days to first symptom appearance, yield per plant and coefficient of infection of YVMD at 80 and 90 days after sowing. The results of correlation and path coefficient analysis revealed that the characters viz., plant height, average fruit weight, number of fruits per plant, crop duration and number of harvest had positive correlation and positive direct effect on yield. Hence, direct selection using these traits would enhance yield. Organoleptic evaluation of all the 34 genotypes were also done. The results revealed the superiority of genotypes IC 15027, IC 15540 and EC 305647 with respect to sensory qualities. The selection of superior genotypes were done based on the characters viz., number of fruits per plant, average fruit weight, fruit length, yield per plant and overall acceptability of organoleptic evaluation. The genotypes viz., IC 15027, IC 15540, EC 305647, EC 305650 and EC 305642 were found superior for these characters even though they were susceptible to the disease. Hence, these genotypes can be crossed with Susthira for developing high yielding YVMD resistant varieties.
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175006