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ondary traits such as husk coverage and tightness, insect resistance, kernel integrity under environmental stress, The incidence and severity of preharvest aflatoxin is greater under and drought tolerance (Lillehoj et al., 1975; Odvody drought conditions, which commonly occur late in the growing season et al., 1997). Genetic variation for response to aflatoxin of south and central Texas. To determine if early maturation could be used as a means of disease escape, aflatoxin contamination was has been found in maize (Widstrom, 1987;Scott and measured in early-, intermediate-, and full-season commercial hybrids Zummo, 1988; Campbell and White, 1995; Betrá n et al., at two Texas locations, Weslaco and College Station. The early and 2002). Sources of resistance include inbred lines Mp420, intermediate hybrids chosen are primarily marketed in midwestern Mp313E, Mp715, Tex6, and population GT-MAS:gk USA while the full-season hybrids are primarily marketed in south-(Scott and Zummo, 1992; McMillian et al., 1993; Windeastern USA. Hybrids were evaluated by inoculating ears 6 to 10 d ham and Williams, 2002). However, the majority of after midsilk with Aspergillus flavus NRRL 3357 using the silk channel these sources of resistance lack agronomic performance, technique and measuring aflatoxin in harvested grain using the VIwhich precludes their direct use in commercial hybrids. CAM Aflatest procedure. Across locations, full-season hybrids had Objectives of several research groups are the transfer lower aflatoxin (mean ϭ 777 ng g Ϫ1 ) levels than intermediate (mean ϭ 1668 ng g Ϫ1 ) and early (mean ϭ 1899 ng g Ϫ1 ) hybrids. There was an of resistance from these sources of resistance to elite inverse correlation between silking date and aflatoxin levels at both inbreds and hybrids and the search for resistance in elite locations (r ϭ Ϫ0.59, P ϭ 0.01 at College Station and r ϭ Ϫ0.58, P ϭ commercial material. There are no commercial hybrids 0.01 at Weslaco). Early and intermediate hybrids had looser husk resistant to aflatoxin. Additionally, information about coverage than full-season hybrids, a characteristic that was positively the comparative aflatoxin accumulation of commercial correlated with aflatoxin levels at both locations. At both locations, hybrids under field conditions in the southeastern USA grain yield was lower with early and intermediate hybrids than with is limited. full-season hybrids. Early maturation in hybrids was insufficient bySeasonal, climatic, biotic, and cultural practices are itself to reduce aflatoxin contamination, but it should be re-evaluated important factors in the development of aflatoxin, and using early maturing hybrids that have good agronomic adaptation to these two Texas growing conditions. F.J. Betrá n, Maize Breeding and Genet. Progr., Texas A&M Univ., College Station, TX 77845; and T. Isakeit, Dep. Plant Pathology and of early-, intermediate-, and full-season commercial hy-Microbiol., Texas A&M Univ., College Station, TX 77843. Received brids at two Texas locations and to estimate the re...

Seventy-two sorghum accessions were randomly selected from the Ethiopia, Mali, Sudan, and Uganda germplasm collections maintained by the US National Plant Germplasm System to evaluate variation in anthracnose resistance. The accessions were planted in a randomized complete block design in College Station, Texas during the 2007 and 2008 growing seasons. Twenty-six accessions exhibited a resistant response across growing seasons with 8 accessions showing a susceptible response. Twenty-nine accessions showed variation in disease response within and between experiments. Seven accessions were rated as resistant in 2007 but showed a susceptible reaction in 2008. The frequency of resistant germplasm varied based on country of origin with 80% of the accessions from Mali, 48% of the accessions from Uganda, 24% of the accessions from Sudan, and 7% of the accessions from Ethiopia exhibiting a resistance response. When the same accessions were evaluated in Isabela, Puerto Rico, 100% of the accessions from Mali, 43% of the accessions from Uganda, and 28% of the accessions from Sudan exhibited a resistant response. All the accessions from Ethiopia were susceptible to anthracnose when evaluated in Isabela, Puerto Rico. In both locations, 22 accessions exhibited a resistant response. Four accessions rated as resistant in Texas were found to be susceptible in Puerto Rico; whereas, five accessions rated as resistant in Puerto Rico showed a susceptible response in Texas. These results indicated that the Mali, Sudan, and Uganda sorghum collections may be an important source of anthracnose resistance. However, the identification of anthracnose resistant germplasm from many diverse regions could result in the identification of new sources of genetic variation for resistance. Also, greater genetic variation for resistance could be present in regions with a high frequency of resistant germplasm.

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Respiration and growth of Pseudomonas putida PpG7, containing catabolic plasmid NAH7, was determined in three agricultural field soils amended with the carbon source salicylate. The addition of salicylate to soil