As water demand for agriculture exceeds water availability, cropping systems need to become more efficient in water usage, such as deployment of cultivars that sustain yield under drought conditions. Soybean cultivars differ in how quickly they wilt during water-deficit stress, and this trait may lead to yield improvement during drought. The objective of this study was to determine the genetic mechanism of canopy wilting in soybean using a mapping population of recombinant inbred lines (RILs) derived from a cross between KS4895 and Jackson. Canopy wilting was rated in three environments using a rating scale of 0 (no wilting) to 100 (severe wilting and plant death). Transgressive segregation was observed for the RIL population with the parents expressing intermediate wilting scores. Using multiple-loci analysis, four quantitative trait loci (QTLs) on molecular linkage groups (MLGs) A2, B2, D2, and F were detected (P

content in maize alone can add an estimated annual gross value of $360 million per year and can go up to Development and adoption of quality protein maize (Zea mays $480 million per year if protein also is increased (John-L.) (QPM) would increase the nutritional value of food and feed son et al., 2001). maize products. Breeding programs at the International Center for The CIMMYT has developed QPM that has im-Maize and Wheat Improvement, Mexico (CIMMYT); Texas A&M University (TAMU); and University of Natal, South Africa (SA) have proved kernel quality characteristics over o 2 /o 2 soft gedeveloped high-lysine inbreds. Information about how elite QPM notypes, by introducing modifier genes and selecting for inbreds of different origins combine and perform in hybrids will facilia hard, vitreous endosperm in o 2 /o 2 germplasm (Vasal, tate the selection of parents and breeding strategies for hybrid devel-2001). The CIMMYT QPM populations, pools, inbreds, opment. Our objectives were to estimate the general (GCA) and and hybrids adapted to subtropical and tropical environspecific combining abilities (SCA) for grain yield and secondary traits ments are widely used in the development of high-lysine among high-lysine inbreds from different sources and to identify pomaize in Brazil, China, Ghana, India, and several Latin tential heterotic relationships among them. Seven white (CML176, American countries (Vasal, 2001). The maize breeding CML181, CML184, Bo59W, Tx807, Tx811, and TxX124) and nineprogram at SA has developed high-lysine white (e.g., yellow QPM inbreds (CML190, CML193, Tx802, Tx814, Tx818, Bo46W and Bo59W) and yellow inbreds (e.g., Do940yMaize Breeding and Genetics Program, Soil and Crop Sciences Dep., Texas A&M Univ., College Station, TX 77843-2474. Received 12 Nov.

Preharvest aflatoxin (AF) contamination by Aspergillus flavus Link:Fr is one of the main limitations for maize (Zea mays, L.) production in the southern USA, causing enormous economic losses and posing a risk to animal and human health. The objectives of this study were (1) to estimate aflatoxin accumulation and expression of associated traits in quality protein maize (QPM) inbreds and their testcrosses, (2) to compute their repeatabilities and correlations, and (3) to study the relationship between inbred lines and their testcrosses for aflatoxin accumulation. Forty-eight inbreds and their testcrosses plus checks were grown in one and three locations in south and central Texas, respectively. Aflatoxin concentration was evaluated in the plants following inoculation with A. flavus. Average aflatoxin concentration overall for inbreds was 286.3 ng g -1 , and for testcrosses 596.5 ng g -1 at Corpus Christi, TX, 325.1 ng g -1 at Weslaco, TX, and 105.1 ng g -1 at College Station, TX. Flinty orange inbreds developed from CIMMYT Population 69 were the least susceptible to aflatoxin accumulation in both inbreds and testcrosses at all locations. Repeatability for aflatoxin was 0.67 in inbreds at Weslaco, TX and 0.54 in testcrosses across locations. Aflatoxin in testcrosses was positively correlated both phenotycally and genotypically with endosperm texture and kernel integrity, and negatively correlated with grain yield and silking date. Less aflatoxin accumulation was associated with flinty endosperm texture, better kernel integrity, and later maturities. Association between the expression of traits in inbreds and aflatoxin in testcrosses was relatively high for endosperm texture (R 2 = 0.62), silking date (R 2 = 0.44), kernel integrity (R 2 = 0.39), and aflatoxin (R 2 = 0.60 for log ng g -1 ). It seems plausible to select for associated traits having high heritabilities and strong correlation with aflatoxin, in addition to low aflatoxin accumulation in inbreds and hybrids to reduce the risk of aflatoxin contamination.

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