Terminal drought induces preharvest aflatoxin contamination (PAC) in peanut. Drought resistance traits are promising as indirect selection tools for improving resistance to PAC. The objectives of this study were to determine the effects of terminal drought on PAC and to investigate the associations between surrogate traits for drought tolerance and PAC. Field tests under rainout shelters were conducted in the dry seasons 2004/2005 and 2005/2006. Eleven peanut genotypes were evaluated under irrigated and terminal drought conditions. Data were recorded for physiological traits, total biomass, pod yield, Aspergillus flavus colonization and PAC. ICGV 98305, ICGV 98330, ICGV 98348, ICGV 98353 and Tifton-8 had low aflatoxin contamination in both years. Traits related to drought resistance were associated well with those related to PAC under drought conditions. Specific leaf area, relative water content, chlorophyll density and drought stress ratings are the best traits for use as indirect selection tools for lower PAC. Breeding for drought tolerance using these traits as selection criteria may help to accelerate progress in developing resistance to PAC.Key words: chlorophyll density -drought stress ratingsdrought tolerance index -indirect selection tools -relative water content -specific leaf area Late season drought on peanuts (Arachis hypogaea L.) generally results in yield reduction, low seed quality, high incidences of Aspergillus flavus colonization and high aflatoxin contamination. Aspergillus flavus colonization during the preharvest period is most important as it can serve as initial inoculum for further A. flavus colonization and, ultimately, aflatoxin contamination. Because aflatoxin is well recognized as a potent carcinogen, reduction of aflatoxin production is an important objective for peanut breeding programmes around the world.Breeding progress for reduction of preharvest aflatoxin contamination (PAC) in peanut using field-based selection approaches have been slow because of large and uncontrollable genotype · environment (G · E) interactions (Holbrook et al. 1994, Anderson et al. 1995, 1996. More consistent and simple traits with lower G · E interactions are worth exploring. A relationship between drought tolerance and reduced PAC has been demonstrated. Some drought-resistant genotypes (Rucker et al. 1995) were observed to have lower PAC when subjected to late season heat and drought stress (Holbrook et al. 2000a). From a breeding point of view, selection for drought tolerance could be an efficient strategy for reducing PAC.Under drought stress, the loss of the capacity of peanut seeds to produce phytoalexins, an immune response to counteract fungal colonization resulted in higher PAC. The ability to maintain higher moisture contents in pods during drought periods may be an important trait enabling cultivars to resist aflatoxin production (Wotton and Strange 1985, Dorner et al. 1989). In addition, drought resistance traits are promising as indirect selection tools for improving resistance to PAC in pean...

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Both restriction fragment length polymorphism (RFLP) and amplified fragment length polymorphism (AFLP) analyses were employed to map a new source of resistance to powdery mildew in mungbean. Disease scores of an F2 population derived from the cross between a moderately resistant breeding line VC1210A and a susceptible wild relative (Vigna radiata var. sublobata, accession TC1966) showed a continuous distribution and was treated as a quantitative trait. Although no significant quantitative trait loci (QTL) that can explain the variation was detected by QTL analysis based on the reconstructed RFLP linkage map, new marker loci associated with resistance were discovered by AFLP analysis. The RFLP loci detected by two of the cloned AFLP bands are associated with resistance and constitute a new linkage group. A major resistance quantitative trait locus was found on this linkage group that accounted for 64.9% of the variation in resistance to powdery mildew. One of the probes developed in this study has the potential to assist in breeding for powdery mildew resistance in mungbean.