Combining ability study for the development of resistance to Aflation contamination by Aspergillus flavus link ex fries in groundnuts

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Mudenda, Mable
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Groundnuts are one of the important household food security crops grown in Zambia. The crop provides minerals, fats, protein, vitamins and it also acts as a source of income for resource poor farmers. Production and utilization of groundnuts in the small holder setting is hampered among others, infection by Aspergillus flavus and subsequent aflatoxin contamination. Although there are several management strategies that may reduce aflatoxin contamination of groundnuts, the pre-eminent strategy for the prevention of aflatoxin is to develop host resistance to Aspergillus flavus. A greenhouse study was, therefore, undertaken at ICRISAT in Lilongwe, Malawi to establish the genetic basis of resistance to aflatoxin contamination by Aspergillus flavus in groundnut genotypes. Ten parental genotypes consisting of three resistant (55-437, J11, Ah 7223) and seven susceptible (Katete, Luena, Natal common, Chalimbana, Chishango, MGV-4 and MGV-5) were crossed in a 3 x 7 North Carolina Design II. F1 crosses were evaluated for aflatoxin contamination levels in a Completely Randomized Design with 3 replications and Aspergillus flavus colony forming units enumerated from the soil. Significant (P<0.05) differences among the crosses for aflatoxin B1 contamination levels and colony forming units measured as propagule density (cfu)g-1 soil were observed. Total aflatoxin B1 contamination levels ranged from 0.2parts per billion (ppb) to 7.3 ppb, while propagule densities of Aspergillus flavus ranged from log(10) 4.11 to 4.78 cfu g-1 soil. Combining ability estimates of the parents for aflatoxin contamination registered significant (P<0.05) negative GCA effects for 55-437(-0.77), Ah 7223 (-1.46) and Katete (-1.95), while specific combining ability effects (SCA) of the crosses for the same trait were significant (P<0.05) and negative for 55-437 x N/Common (-1.43), J11 x Luena (-1.21), J11 x Katete (-1.81) and Ah 7223 x N/Common (-1.81). The narrow sense heritability (h2) estimates were in the range of 0.1 and 0.2, while the Baker‘s ratio ranged between 0.2 and 0.3, suggesting the influence of non-additive gene action in controlling the resistance to aflatoxin contamination by Aspergillus flavus. The study thus concluded that improvement of resistance to aflatoxin contamination can be achieved via a recurrent selection procedure.
Aflatoxin Contamination