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.)

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.

GENETIC VARIABILITY FOR RESISTANCE TO CERCOSPORA LEAF SPOTS IN GROUNDNUT (Arachis hypogaea L.)

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