GENETIC VARIABILITY FOR RESISTANCE TO CERCOSPORA LEAF SPOTS IN GROUNDNUT (Arachis hypogaea L.)
GENETIC VARIABILITY FOR RESISTANCE TO CERCOSPORA LEAF SPOTS IN GROUNDNUT (Arachis hypogaea L.)
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Date
2006-06
Authors
ABUBAKAR, HAMASSELBE
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Abstract
Leaf spot diseases of groundnut caused by Cercospora arachidicola, Hori
(early leaf spot) and Cercosporidium personatum (Berk and Curt) Deighton (late leaf
spot) are serious causes of yield losses in West and Central Africa. Host plant
resistance is the most economical, sustainable and environmentally friendly
approach to manage leaf spot diseases. A field experiment was conducted in 2001
and 2002 at Samaru, Nigeria and Guiring, Cameroon to identify sources of
resistance, estimate genetic variability for resistance to Cercospora leaf spots, yield
and yield components as well as their relationship with Cercospora incidence. The
Groundnut Germplasm Project (GGP) nine-point field scale was used to assess
Cercospora severity. The genotypes were grouped into various classes of resistance
to leaf spots using the method suggested by the West and Central African Council
for Agricultural Research and Development (WECARD). Genotypic coefficients of
variability, broad sense heritability, genetic gain and correlation coefficients between
disease incidence and some agronomic traits were estimated by the variance
components procedure. The genotypic coefficients of variability were low, while
heritability estimates were high except for fodder yield. The estimates of genetic gain
were low except for Cercospora severity at 75 days after sowing (DAS) and fodder
yield. No strong inherent association was found between Cercospora incidence and
all the agronomic traits studied except for Cercospora severity at harvest and fodder
yield at Guiring. Resistance to early and late leaf spots was not stable among
genotypes and across environmental conditions. The genotypes SAMNUT 10,
SAMNUT 21, 28-206, NC-GP 343, #3-94, ICGV 91225, ICGMS 42, ICG 6902,
SAMNUT 11, SAMNUT 22 were found to be resistant to early leaf spot at Samaru,
while ICGV 91225 was resistant at Guiring. None of the genotypes tested was
resistant to late leaf spot in both locations. In breeding for resistance to leaf spot
diseases, the genotypes that were resistant or performed better than the tolerant
check SAMNUT 11 could be used as donor parents. Therefore, the potential
parents that can be used for breeding for resistance to early leaf spot are SAMNUT
10, SAMNUT 21, 28-206, NC-GP 343, #3-94, ICGV 91225, ICGMS 42, ICG 6902,
SAMNUT 11, SAMNUT 22 at Samaru and ICGV 91225 at Guiring. The promising
sources for resistance to late leaf spot are 28-206, SAMNUT 10, ICGV 91225 at
Samaru and ICG 6902, # 3-94, SAMNUT 22, SAMNUT 21, NC-GP 343, ICGV
91225, ICGMS 42, SAMNUT 10 at Guiring.
Description
A thesis submitted to the Postgraduate School
Ahmadu Bello University in partial fulfillment
of the requirements for the Degree of Master of
Science in Plant Breeding
Department of Plant Science,
Faculty of Agriculture,
Ahmadu Bello University
JUNE, 2006
Keywords
GENETIC,, VARIABILITY,, RESISTANCE,, CERCOSPORA,, LEAF,, SPOTS,, GROUNDNUT,, (Arachis hypogaea L.).