Assessment of resistance against bacterial wilt in marigold genotypes under humid tropics
Abstract
Bacterial wilt of marigold caused by Ralstonia solanacearum is a highly devastating disease that limits successful cultivation of marigold under humid tropics. With the objective to screen genotypes of different Tagetes species for resistance to bacterial wilt, the present study was conducted at the Department of Floriculture & Landscaping, College of Horticulture, Thrissur, Kerala, India in two seasons viz., rainy and winter, during 2018-19. Thirty two marigold genotypes were subjected to field evaluation in a wilt sick plot. Among the genotypes, there were eight F1 hybrids, eight varieties, seven local collections of T. erecta, eight genotypes of T. patula (including three varieties and five local collections) and one genotype of T. tenuifolia. The study revealed that two local collections of T. erecta viz., M-1 and M-2 were completely resistant to bacterial wilt. The resistance of these two local collections to bacterial wilt was also confirmed by artificial screening studies. It was also observed that bacterial wilt incidence was severe during winter season compared to monsoon. As per the result of screening conducted during rainy season, there were four resistant genotypes, five moderately resistant types, five moderately susceptible types, ten susceptible types and eight highly susceptible types while during winter season the number of highly susceptible types recorded was 20, along with eight susceptible types, two moderately susceptible types and two resistant types. During rainy season, flavonoid content in both leaves and petals was highest in M-1, M-2 and was on par with Bhagwati, which showed a PDI of 4.16% in field evaluation. Resistance to bacterial wilt was negatively correlated with flavonoid content in leaves and petals.Downloads
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