EXAMINATION OF MITOTIC STABILITY AND HYBRIDIZATION POTENTIAL BETWEEN 2 GENETICALLY DISTINCT HAPLOTYPES OF MAGNAPORTHE-GRISEA

MGR586 DNA fingerprinting was used to examine the mitotic stability an d hybridization potential of two genetically distinct haplotypes of Ma gnaporthe grisea under laboratory conditions. Two isolates representin g a haplotype in each of two different MGR586 DNA-fingerprinting group s (A and D) commonly found on rice in Arkansas, were grown singly or i n coculture on solid medium, liquid medium, or on coinoculated rice le aves. A total of 355 monoconidial cultures were recovered at various t imes and examined for their MGR586 DNA fingerprints. The majority of t he 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 fingerprint s of these haplotypes differed by only 1-5% from the parental haplotyp es. Of 97 isolates recovered from solid medium, a single nonparental h aplotype was identified from the coculture treatment after 171 days. O f the 200 isolates recovered from liquid medium, 15 were nonparental t ypes and represented seven different haplotypes. Of these, a single no nparental isolate was recovered from the parental haplotype D isolate grown singly after 67 days. The other 14 nonparental isolates were rec overed from the coculture treatment; 3 were recovered after 38 days, 4 after 67 days, and 7 after 162 days. Thus, the nonparental variants w ere recovered much more frequently from the cocultured treatment. The appearance of the nonparental haplotypes may be due to hybridization b etween the two haplotypes. However, other factors such as a higher mut ation in coculture cannot be ruled out as a possible explanation for t hese data. All isolates recovered from a lesion from coinoculated rice leaves were one haplotype. The data indicate that there was competiti on in both artificial media and host tissue between the two MGR586 hap lotypes. (C) 1995 Academic Press, Inc.