Screening of Maize Genotypes against Southern Leaf Blight ( Bipolaris m aydis ) during Summer Season in Nepal

A study was conducted from 29 March 2014 to 27 July 2014 at the Institute of Agriculture and Animal Science, Paklihawa, Rupandehi with the objective of screening 13 maize genotypes against southern leaf blight caused by Bipolaris maydis . Field experiment was laid out in a randomized complete block design with three replications. Disease scoring was done as percentage of leaf area infected on individual plant at 5 days intervals starting from 63 days after sowing, for 3 times, and disease severity and mean AUDPC were calculated and yield was recorded. Among the tested genotypes, disease severity varies significantly. Disease symptoms appeared first in Yellow Popcorn, 64.00 days after sowing (DAS) with the highest severity and at last in RML-32/RML-17 (79.00 DAS) with the least score in field. The 13 genotypes differed significantly in mean AUDPC values. RML-32/RML-17 (AUDPC value 5.90) appeared most resistant, followed by RML-4/RML-17 (AUDPC value 11.50), while Yellow Popcorn (AUDPC value 71.99) was most susceptible among the tested genotypes. Highest maize yield (3.43 metric ton ha -1 ) was also recorded on RML-32/RML-17 and least (0.75 metric ton ha -1 ) on Yellow Popcorn. Maximum SPAD value above cob was recorded in RML-4/RML-17 (45.62) followed by S03TLYQ-AB-01 (44.88) while minimum in Yellow popcorn (30.60). So, Yellow popcorn has the highest (3.16) and RML-32/RML-17 (0.08) lowest total AUDPC above cob. Similarly maximum SPAD value below cob was recorded in RML-4/RML-17 (44.37), while minimum in Yellow popcorn (28.82). So, Yellow popcorn has the highest (8.75) and RML-32/RML-17 (0.41) has lowest total AUDPC below cob. The genotypes RML-4/RML-17 and RML-32/RML-17 appeared resistant to SLB with maximum yield. These genotypes could be used as the sources of resistance in breeding program and could be developed to resistant varieties grown under tropical and subtropical climatic conditions during summer season. The genotype Yellow popcorn being highly susceptible to SLB with a maximum mean AUDPC and minimum yield, can be used as susceptible check for breeding purpose and different varietal screening.