The fungus Sclerotinia trifoliorum plagues legume crops worldwide. But chickpeas seem to have escaped its wrath, with the exception of Australia's crop. Now, that's no longer the case, report Agricultural Research Service (ARS) and collaborative university scientists.
During the 2005-2006 chickpea growing season in central California, the team observed stem and crown rots reminiscent of Sclerotinia infection. But subtle irregularities in the symptoms led the researchers to believe their prime suspect — S. sclerotiorum, which infects more 400 plant species — had an accomplice, namely S. trifoliorum.
ARS research plant pathologist Weidong Chen led the team, which included Fred Muehlbauer (now retired) with the ARS Grain Legume Genetics Physiology Research Unit in Pullman, Wash., and University of California-Davis and Washington State University researchers.
They examined 10 Sclerotinia isolates from their collection from chickpea stems and subjected each to three identification criteria: growth rate, ascospore morphology and DNA markers indicative of S. trifoliorum. The team's analysis showed that S. trifoliorum isolates were slower-growing, displayed "ascospore dimorphism," which is the formation of two versions of the same spore type, and harbored a set of group I intron markers while S. sclerotiorum did not.
Chen suspects S. trifoliorum's occurrence on central California chickpeas stems from prior plantings of alfalfa — another legume host — and not an accidental introduction from Australia, the only continent where the fungus has previously been reported on chickpea. Identification of this new chickpea pathogen should aid in improving disease-management practices and developing resistant chickpea cultivars for farmers.
More information on this initiative is available at ARS National Sclerotinia Initiative.
The research study was published recently in the journal Plant Disease, and is available online.
ARS is a scientific research agency of the U.S. Department of Agriculture.