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*, ***, **** Significantly different from zero at p < 0.05, p < 0.001 and p < 0.0001 levels, respectively aHusk cover: A scale of 1 to 5, where 1 = very tight husk extending well beyond the ear tip and 5 = exposed ear tip.

bPlant aspect (1-5): 1 = excellent overall phenotypic appeal and 5 = poor overall phenotypic appeal. cEar aspect (1-5): 1 = clean, uniform, large, and well-filled ears and 5 = rotten, variable, small and partially filled ears.

dEar rot (1-5): 1 = little or no visible ear rot and 5 = extensive visible ear rot.

eDisease scores recorded at 26 days after mid-silking on a 1-5 scale, where 1 = no visible infection and 5 = severe infection on all leaves.

*, ***, **** Significantly different from zero at p < 0.05, p < 0.001 and p < 0.0001 levels, respectively aHusk cover: A scale of 1 to 5, where 1 = very tight husk extending well beyond the ear tip and 5 = exposed ear tip.

bPlant aspect (1-5): 1 = excellent overall phenotypic appeal and 5 = poor overall phenotypic appeal. cEar aspect (1-5): 1 = clean, uniform, large, and well-filled ears and 5 = rotten, variable, small and partially filled ears.

dEar rot (1-5): 1 = little or no visible ear rot and 5 = extensive visible ear rot.

eDisease scores recorded at 26 days after mid-silking on a 1-5 scale, where 1 = no visible infection and 5 = severe infection on all leaves.

endosperm proteins associated with lower levels of accumulated aflatoxin has relied on side-by-side comparisons of lines with genotypes with different genetic backgrounds (Chen et al, 2004, a,b). The identification of genetically similar lines differing significantly in aflatoxin accumulation should enable the identification of candidate genes underlying resistance to A. flavus infection and/or reduction of aflatoxin production without the confounding effects that result when lines of diverse genetic background are compared (Brown et al., 2003). Comparing pairs of genetically similar lines in a proteome analysis, has thus far identified several resistance-associated proteins, categorized as stress-related, and a putative regulatory protein (Brown et al., 2003). The expression of stress-related proteins may enable a plant to defend against fungal invasion under stress conditions. Extensive analysis of kernel endosperm proteins of several pairs of genetically similar lines emanating from our collaborative breeding project are described elsewhere (Brown et al., 2007). This may facilitate identification of potential markers for rapid screening of genetic materials in a breeding program. Proteins identified in such a screen may be useful markers for rapidly screening genetic materials in a breeding program.

Evaluating agronomic performance of selected lines

Inbred lines that accumulate less aflatoxin need to be evaluated for agronomic performance as inbred lines per se and as parents of hybrids to determine their usefulness in a breeding program. We screened 54 inbred lines for aflatoxin accumulation under field conditions at Saminaka and Ikenne, Nigeria in 2004. Principal component analysis was used to evaluate the field data and to assess the performance of the new inbred lines on the basis of their agronomic traits. The first principal component axis (PC1) accounted for nearly 40% of the total variation in the data set (Table 4). A high PC1 score was associated with significant reduction in ear height, poor husk cover, plant aspect and ear aspect scores, and increased ear rot, leaf blight and leaf rust infec-

Table 5. Mean aflatoxin values (ng/g) of inbred maize lines selected for low aflatoxin production in the kernel screening assay (KSA) and evaluated under artificial inoculation in the field at Ibadan, Nigeria in 2003 and 2004.

Inbred line

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