Response of cotton genotypes against the incidence of Alternaria leaf blight of cotton under field conditions

Abstract

Aim: To identify the resistant source present in the breeding materials against Alternaria leaf blight disease of cotton (Gossypium spp.). Methodology: Breeding entries were sown in a randomized complete block design in the experimental site. Disease intensity on each genotype at 45, 90, 135 and 180 days after sowing (DAS) were recorded from leaves of lower, middle and upper parts of plants and graded. According to 0 - 4 disease scoring scale, per cent disease index (PDI) was calculated and genotypes were categorized into different categories based on disease reaction Results: Development of Alternaria disease was noticed at early days of crop growth in few genotypes and the disease increased upto 135 days after sowing. The maximum mean per cent disease index of 41.17 and 40.06 were recorded in Br.14a (ZT)1333 and Br.14a (ZT)1332 respectively. The least PDI of 0.58 was recorded in Br.03a (ZT)1303. Disease incidence of <11.00% of was reported in 37 entries at 45 days after sowing. None of the genotypes showed apparently immune reaction, twenty-one genotypes showed resistant reaction, eleven genotypes were moderately resistant and five showed moderately susceptible reaction. Interpretation: Twenty-one breeding lines showed resistant reaction against Alternaria leaf blight disease under field conditions, however, further utilization of these lines may be carried out in breeding programmes for the development of resistant source against this disease.