GENETIC ANALYSES OF RESISTANCE TO LATE LEAF SPOT AND RUST VIS-A-VIS PRODUCTIVITY IN GROUNDNUT (Arachis hypogaea L.)
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Date
2001
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University of Agricultural Science, Dharwad
Abstract
"Evaluation of 100-groundnut germplasm revealed inter-specific
derivatives and mutants as the most potential source of resistance to late leaf
spot (LLS) and rust. Components of resistance were more reliable than field
disease scores in assessing resistance in germplasm. Though resistance was
strongly associated with late maturity, mutants and second cycle interspecific
derivatives combined resistance and early maturity.
Resistant mutants isolated from VL 1 were grouped in to three distinct
clusters. Late leaf spot resistant mutants were susceptible to rust and had
more branches; higher seed mass and pod yield and reduced leaf size. An
opposite trend was evident with rust resistant mutants indicating their
pleiotrophic nature.
Evaluation of 10 selected genotypes revealed significant variation for
yield loss. Besides resistance parameters, physiological attributes viz., growth
rates and partitioning contributed to reduction in yield loss. Late sowing was
ideal for disease screening. An inter-specific derivative (D 39d) and a mutant
(28-2) combined resistance with high yield and early maturity and they were
superior to cultivated varieties. D 39d was also superior in oil quality.
Physiological analyses of 3deld loss variation indicated predominant role
for sink than source in determining the yield potential of genotypes.
Significant interaction between LLS and rust revealed a need for evaluation of
genetic material both under natural, where they occur together, as well as
individual disease conditions.
Two sets of duplicate-complementary recessive genes independently
determined resistance to LLS and rust in inter-specific derivatives and
mutants.
A combination of isozyme (Glutamate Oxaloacetate Transaminase) and
protein (seed and hjrpocotyl) profiles could be used uniquely to fingerprint
selected genotypes. Polymorphism for peroxidase in resistant and
susceptible variants indicated its potential for marker-assisted selection.
Peroxidase activity also revealed inducible and constitutive nature of LLS
resistance in mutants and inter-specific derivatives, respectively."
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