GENETIC ANALYSIS OF AFLATOXIN AND AGRONOMIC TRAITS IN GROUNDNUT (ARACHIS HYPOGAEA L.)

GENETIC ANALYSIS OF AFLATOXIN AND AGRONOMIC TRAITS IN GROUNDNUT (ARACHIS HYPOGAEA L.)

Abstract:

Groundnut (Arachis hypogaea L.) is one of the major crops susceptible to Aspergillus flavus infection and subsequent aflatoxin contamination which adversely affects its production and utilization in the small holder setting. 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 A. flavus. The objectives of this study were to determine the level of resistance to A. flavus and aflatoxin accumulation among selected groundnut genotypes, to assess the mode of gene action controlling resistance to aflatoxin accumulation and agronomic traits and to estimate heritability for resistance to A. flavus and aflatoxin accumulation. Eight groundnut varieties comprising of three A. flavus resistant lines and five susceptible varieties were obtained from Institute for Agricultural Research, Samaru. The genotypes were crossed in a 3 x 5 North Carolina (NC II) design II fashion to generate 15 F1 hybrids. The F1 seeds were selfed to F2 and then evaluated alongside the eight parents for twelve quantitative characters using randomised complete block design (RCBD) with three replications at the Department of Plant Science screen-house under artificial A. flavus inoculation. Analysis of variance revealed significant (P≤0.05) differences among the groundnut genotypes for all traits except for 100-kernel weight and shelling percentage. The mean performance of the parents showed that SAMNUT 22 (2.50 ng / g ), ICGV 91317 (6.31 ng / g ) and ICGV 91324 (12.23 ng / g ) recorded lowest aflatoxin accumulation value of less than 20.00 ng / g and the crosses: SAMNUT 26 x ICGV 91317 (0.8 ng / g ), SAMNUT 26 x ICGV 91328 (1.2 ng / g ), SAMNUT 25 x ICGV 91324 (3.92ng/g), SAMNUT 22 x ICGV 91328 (4.4 ng / g ) and SAMNUT 22 x ICGV 91324 (12.3 ng / g ), as the best for resistance to A. flavus infection and aflatoxin accumulation under the United States Food and Drug Administration, which sets the limit of aflatoxin in food and feeds at 20 ng/g. The general (GCA) and specific (SCA) combining abilities were significant (P≤0.05) for most characters indicating the role of both additive and non-additive gene effects in the expression of most characters. High broad-sense heritability values were obtained for days to 50% flowering (88.9%), plant height (84.0%), haulm weight (86.8%), kernel infection (85.3%) and aflatoxin accumulation (99.7%). The parental genotypes, SAMNUT 23, SAMNUT 24, SAMNUT 25, SAMNUT 26, ICGV 91324, ICGV 91328 were good general combiners for aflatoxin B1 accumulation. Among the progenies, SAMNUT 22 x ICGV 91324 and SAMNUT 23 x ICGV 91317 with positive SCA effects for haulm weight and negative SCA effects for kernel infection and aflatoxin accumulation. A. flavus infection among the parents and progenies correlates poorly to aflatoxin contamination. The study revealed that non-additive gene action was more important than additive gene action for resistance to A. flavus infection, while additive gene action was more predominant for resistance to aflatoxin accumulation. The information provided from this study could be utilized in planning breeding programme for the development of groundnuts with improved pod yield, haulm yield, resistance to A. flavus infection and aflatoxin accumulation.

GENETIC ANALYSIS OF AFLATOXIN AND AGRONOMIC TRAITS IN GROUNDNUT (ARACHIS HYPOGAEA L.)