September 6, 2010

US researchers develop fungal-resistant corn lines

Corn germplasm lines developed by USDA scientists are scoring high marks in field trials for resistance to aflatoxin produced by Aspergilllus flavus and A. parasiticus fungi.

According to USDA's Agricultural Research Service (ARS) geneticist Paul Williams, the presence of aflatoxin in corn greatly reduces its value and marketability. Annual losses incurred by the corn industry to aflatoxin contamination of kernels are estimated at US$192 million.

Williams is part of a multidisciplinary team of researchers and university cooperators that is developing new corn lines that are genetically resistant to aflatoxin-producing fungi.

In 2008 field trials, two germplasm lines that the team developed - Mp715 and Mp717 - showed the highest levels yet of resistance to aflatoxin contamination. A more recent line, Mp04:097, also performed well in 2009 trials.

Mp715 and Mp717 are also resistant to the accumulation of another fungal toxin-fumonisin, which is produced by Fusarium verticillioides. The toxin causes neurological abnormalities in horses after they consume infected corn.

According to Williams, the lines have been widely requested and used in plant breeding programmes at state, federal and international research institutions, plus three major commercial seed companies and several smaller ones.

In related work, the researchers are mapping chromosome regions associated with aflatoxin-resistance in crosses between resistant lines and susceptible ones with good agronomic qualities. The goal is to identify markers that can be used in marker-assisted breeding.

In addition, the team has developed corn lines that resist fall armyworms and southwestern corn borers, insect pests whose feeding damage can contribute to aflatoxin contamination.