Examination of Mitotic Stability and Hybridization Potential between Two Genetically Distinct Haplotypes of Magnaporthe grisea

Xia, J. Q. and Correll, J. C. 1995. Examination of mitotic stability and hybridization potential between two genetically distinct haplotypes of Magnaporthe grisea. Experimental Mycology 19, 171-177. MGR586 DNA fingerprinting was used to examine the mitotic stability and hybridization potential of two genetically distinct haplotypes of Magnaporthe grisea under laboratory conditions. Two isolates representing a haplotype in each of two different MGR586 DNA-fingerprinting groups (A and D) commonly found on rice in Arkansas, were grown singly or in coculture on solid medium, liquid medium, or on coinoculated rice leaves. A total of 355 monoconidial cultures were recovered at various times and examined for their MGR586 DNA fingerprints. The majority of the isolates of the two MGR586 DNA haplotypes remained stable over the 162-to 171-day study period. However, 16 isolates recovered belonged to one of seven nonparental haplotypes identified; the DNA fingerprints of these haplotypes differed by only 1-5% from the parental haplotypes. Of 97 isolates recovered from solid medium, a single nonparental haplotype was identified from the coculture treatment after 171 days. Of the 200 isolates recovered from liquid medium, 15 were nonparental types and represented seven different haplotypes. Of these, a single nonparental isolate was recovered from the parental haplotype D isolate grown singly after 67 days. The other 14 nonparental isolates were recovered from the coculture treatment; 3 were recovered after 38 days, 4 after 67 days, and 7 after 162 days. Thus, the nonparental variants were recovered much more frequently from the cocultured treatment. The appearance of the nonparental haplotypes may be due to hybridization between the two haplotypes. However, other factors such as a higher mutation in coculture cannot be ruled out as a possible explanation for these data. All isolates recovered from a lesion from coinoculated rice leaves were one haplotype. The data indicate that there was competition in both artificial media and host tissue between the two MGR586 haplotypes.