Screening of Maize Genotypes against Southern Leaf Blight (Bipolaris Maydis) during summer in Rampur, Chitwan
Abstract
Screening of 20 maize genotypes against Southern Leaf Blight of maize (Bipolaris maydis (Nisik) Shoemaker) was carried out in RCBD in National Maize Research Program, Rampur, Nepal during June to September, 2015. The area of research field was 315 m2. Each genotype had two rows per plot of 7.5m2 with two replication. Disease incidence was taken for three times at 43, 53 and 63 DAS. Disease scoring was done as percentage of leaf area infected on individual plant at 7 days interval starting from 58 days after sowing for 5 times and disease severity and mean AUDPC was calculated. Also the yield was calculated. Shade house experiment was carried out in a Completely Randomized Design with 3 replication on 20 genotypes by artificial inoculation at 3-4 leaf stage with a pure culture suspension of Bipolaris maydis (4x104conidia per ml) .and disease incidence and survival days of plant were recorded. Among the genotypes disease severity varied in the field. Highly significant differences were observed among the genotypes for Southern Leaf Blight severity, Area Under Disease Progress Curve and grain yield. Genotypes with mean AUDPC values from 200-250, 250-300 and above 300 were categorized as moderately resistant, moderately susceptible and susceptible. Disease severity was highest on genotype Rampur 24, 07 SADVI and lowest on BGBYPOP, RML-32/RM-17 and RAMS03F08. Highest maize yield (4.44 ton/ha) was recorded on RML-32/RML-17 and least (1.41 ton/ha) was obtained in ZM-627.In shade house, Rampur-24 followed by 07 SADVI, Rampur 27 died earlier and RML-32/RML-17 and BGBYPOP survived to the longest periods after inoculation. Disease Susceptibility pattern was similar in both field and shade house condition. The genotypes RML-32/RML-17, BGBYPOP, RAMS03F08 and TLBRS07F16 could be developed as resistant varieties to Southern Leaf Blight of maize and also as high yielders during summer under Chitwan and similar conditions.
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Introduction
Maize (Zea mays L.)is one of the most important cereal crops of the world grown in the irrigated and rainfed areas which ranks third after wheat and rice. Due to its high potentiality than any other cereals, it is also called as a versatile and miracle crop so it is popularly known as’ Queen of Cereals’(Singh, 2002).It is the second most important crop after rice in terms of area and production and productivity (2.46 ton/ha) in Nepal. There is a wide gap between potential yield of maize varieties having 6.7 t/ha (on-station experimental yield), attainable yield of about 5.7 t/ha (on farm yield with improved practices) and national yield of 2.4 t/ha [1]. Among many,the most important factor for causing this wide gap in yield is SLB of maize caused by B.maydis syn. Helminthosporium maydis (Teliomorph: Cochliobolous heterostrophus).This disease was identified in 1965 from Rampur, Chitwan for the first time in Nepal [6].There are three physiological races of C.heterostrophus, they are Race O, T and C. The most prevalent race is O which attacks abroad range of genotypes. In maize, one recessive major gene for resistance has been identified namely rhm 1 which confers resistance to race Oof C. heterostrophus [3,12].In the adult plant rhm 1 confers a level of quantitative resistance[2,11].Disease data in experimental trail and disease situation in farmer’sfield support the need for screening the genotypes against SLB [8].The use of fungicides is costly and environment unfriendly and it is simple, effective, safe and economical to use resistant varieties for controlling this disease. In such contest, identification of resistant genotypes/varieties would be good alternatives to manage SLB. The study was conducted with following objectives
• To determine the SLB disease incidence and disease severity of maize infield under epiphytotic condition.
• To determine the seedling incidence of SLB disease under shade house condition.
• To identify resistant and susceptible genotypes of maize against SLB disease
Conclusion
Among 20 maize genotypes, BGBYPOP, RML-32/RML-17 and RAMS03F08 were resistant to southern leaf blight of maize with lower disease severity and higher yield. These genotypes could be used as resistant varieties and can be used as sources of resistance for breeding. The genotypes like Rampur-24, 07 SADVI were highly susceptible to southern leaf blight of maize with maximum disease severity and mean AUDPC value. These genotypes can be used as susceptible check.Rampur-28, Rampur-27 and Rampur-32 had higher disease incidence and severity but grain yield was statistically similar with high yielders and the resistance genotypes BGBYPOP, RAMS03F08.Hence they can be used as tolerant genotypes against SLB.
