ARS | Publication request: GENETIC DIVERSITY AND VIRULENCE OF RHIZOCTONIA SPECIES ASSOCIATED WITH PLANTINGS OF LOTUS CORNICULATUS

Submitted to: Mycological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 16, 2001
Publication Date: February 1, 2003
Citation: EMERY, K.M., BEUSELINCK, P.R., ENGLISH, J.T. GENETIC DIVERSITY AND VIRULENCE OF RHIZOCTONIA SPECIES ASSOCIATED WITH PLANTINGS OF LOTUS CORNICULATUS. MYCOLOGICAL RESEARCH. 2003. v. 107. p. 183-189.

Interpretive Summary: Birdsfoot trefoil (Lotus corniculatus L.) is a plant that is grown as a high-quality feed for livestock. In humid locations, birdsfoot trefoil population survival often is limited primarily by Rhizoctonia spp., a group of fungi that can cause serious damage to birdsfoot trefoil leaves and shoots, and can result in plant death. The purpose of our research was to characterize genetic variation and virulence in populations of Rhizoctonia solani and binucleate Rhizoctonia associated with diseased L. corniculatus in field plantings over a period of several years. We were able to isolate different forms of R. solani recovered from diseased leaf and shoot tissues, while isolates of binucleate Rhizoctonia were recovered predominantly from soil and associated plant debris. The isolates of R. solani were more virulent on leaves and shoots of L. corniculatus than were binucleate Rhizoctonia isolates. There was less genetic variation in the isolates of R. solani than the binucleate Rhizoctonia. This research is important to plant breeders and geneticists seeking to develop birdsfoot trefoil with greater disease resistance, since it becomes more efficient to select against the more virulent and more genetically stable R. solani.

Technical Abstract: Species of Rhizoctonia cause a blight of Lotus corniculatus, a perennial forage legume. We characterized genetic variation and virulence in populations of Rhizoctonia solani and binucleate Rhizoctonia associated with diseased L. corniculatus in field plantings over a period of several years. Isolates of anastomosis groups AG-1 and AG-4 accounted for the R. solani recovered from diseased leaf and shoot tissues. Isolates of binucleate Rhizoctonia were recovered predominantly from soil and associated plant debris. Isolates of R. solani were more virulent on leaves and shoots of L. corniculatus than were binucleate Rhizoctonia isolates. Numerous unique DNA restriction patterns were observed among binucleate isolates and anastomosis groups of R. solani. Variation in restriction patterns was greater among isolates of AG-1 from the lower plant canopy than from the upper canopy. No restriction pattern was shared by any isolate from AG-1 and AG-4. Allelic and genotypic heterogeneity of AG-1 isolates were also greater in the lower plant canopy. Binucleate isolates exhibited greater heterogeneity than AG-1 isolates from either canopy region. Lotus corniculatus offers significant opportunities for investigating temporal and spatial dynamics of genetic structure of Rhizoctonia populations in perennial plant systems.