Assessement and Genetic characterisation of Maize (Zea mays L.) Germplasm for leaf blight(Helminthosporium turcicum pass.)
Date
2011-03-17
Authors
Simelane, Victor B
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Abstract
Maize leaf blight caused by the fungus Helminthosporium turcicum (Exerohilum
turcicum) is one of the constraints affecting maize production and thereby eroding
income and food security in Zambia and the Southern African region. Maize leaf blight
severity on susceptible varieties can range between 40-70% plant coverage and can
reduce maize yields by up to 60% when infection is high. Six FI maize hybrids and their
p2 populations were evaluated for leaf blight resistance in 2006 and 2007 at the Golden
Valley Agricultural Research Trust, Chisamba, Zambia. They were artificially
inoculation with the pathogen. Disease resistance parameters used to assess the disease
included, disease severity scores, percent affected ear leaf area, number of lesions, lesion
sizes, incubation periods, area under disease progress curve and apparent infection rates.
From the FI'S evaluation, disease resistance parameters indicated that hybrids J34-2 and
J34-4 were the most susceptible and J34-1 and J34-3 were most resistant hybrids
respectively. All f-i populations showed continuous variation for leaf blight resistance.
Variability parameters namely genetic coefficient of variation (GCV), broad sense
heritability (h2b) and genetic advance (GA) as measured by the resistance parameters
were used to determine the gene action for leaf blight resistance on individual
populations. The variability parameters revealed that in populations J34-1, J34-2, J34-3
and J34-5 leaf blight resistance was under additive gene action, while in populations J344
and J34-6 they revealed that leaf blight resistance was under non additive gene action.
In all cases genotypic correlations in general, were higher than the corresponding
phenotypic correlations, indicating little influence of the environment on any inherent
association among the traits studied. Male flowering dates were found to be significantly
but negatively correlated with most disease resistance parameters, indicating that such a
trait could be used indirectly for the improvement of leaf blight resistance in maize. The
inferences of the results of the present study and possible implications in maize breeding
for leaf blight resistance have been discussed.
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Keywords
Maize , Assessment and Genetic Characterisation of Maize