LINDELL BEACH, B.C. – Scientists have discovered a gene in corn that appears to be able to resist three troublesome leaf diseases.
The gene, glutathione S-transferase (GST), seems to be able to counteract the devastating fungal diseases southern leaf blight, grey leaf spot and northern leaf blight, all of which can cripple corn crops.
The findings of plant pathologists and crop scientists from North Carolina State University (NCSU) have been published in the Proceedings of the National Academy of Sciences.
All three diseases are caused by necrotrophic fungi, which is fungi that kills what they eat.
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Southern corn leaf blight is a problem in the southeastern United States, southeast Asia, southern Europe and parts of Africa.
In hot, humid climates, it causes brown spots on leaves that get larger and spread to the whole plant. Severe infections will cause major crop losses.
Northern leaf blight can be found in the Midwest U.S. corn belt and causes cigar-shaped lesions, while grey leaf spot is found in the Midwest and the southeastern U.S.
“Disease resistance is important for all plants, cultivated and wild,” said Peter Balint-Kurti, a research plant pathologist and geneticist for the U.S. Department of Agriculture who works in the NCSU’s plant pathology and crop science departments.
“All, or almost all, the resistance genes we use in cultivated varieties evolved in the wild progenitors of the crop. In fact, it is common to go back to wild relatives when looking for genes for resistance to new diseases that emerge from time to time.”
He said researchers tested the lines for resistance to the three diseases and found that a line resistant to one disease is probably also resistant to the other two.
Researching the mechanics behind the complexities of disease resistance can offer help to plant breeders and farmers.
“We are working on identifying genes,” said Balint-Kurti.
“We are looking at understanding the genetics of the defence response.”
NCSU researchers joined lead author Randy Wisser, an assistant professor at the University of Delaware, and other researchers from UD, Cornell University and Kansas State University in examining 300 corn varieties.
The wide diversity allowed scientists to zero in on the regions of the genome responsible for triggering resistance to the three diseases and also identify those varieties that are particularly resistant.
“The GST gene implicated in our study belongs to a multi-gene family,” said Wisser.
“It is a member of a family of genes for which there are multiple (nonidentical) copies in the genome. The primary function associated with this gene family is detoxification. In order for multiple resistance to occur, we hypothesize that the pathogens share certain aspects of pathogenesis, allowing the host to use a common mechanism to resist disease.”
Wisser said that because detoxification is a basic process in maintaining cellular health, the researchers think resistance is conditioned by a detoxification-based mechanism.
However, he stressed that the gene does not give complete resistance.
“This is not a silver bullet for multiple or even single disease resistance breeding. There are likely to be many different genes with similarly small sized effects that contribute to the overall level of resistance, but they may act through diverse mechanisms of action.”
The study is one of the most comprehensive analyses of multiple disease resistance in plants.
“We are almost certain that something in the vicinity of the GST gene we identified is conferring resistance,” said Balint-Kurti.
“We are not absolutely sure that the GST gene itself is the important gene. It could be another gene right next to it. We are working on validating the GST gene and once we have done that we need to figure out how it confers resistance and how come it confers more resistance than other, slightly different versions of the same gene.”
Plants are constantly challenged by the threat of disease that can be triggered by different environmental conditions.
Some fungal diseases may like conditions to be cool, others like it hot and most like it wet. Some need the plant to be at a certain growth stage or to be stressed.
The fungal spores may come from detritus in the soil left over from last year or they may be windblown from other areas.
The threat of climate change may eventually add to the impact of pathogens and a plant’s resistance.
“Climate is important for disease development,” said Balint-Kurti.
“It’s difficult to say how climate change will affect (pathogens), but it’s safe to say it will affect it somehow.”
