Variation of high and low recombination frequencies in Neurospora crassa owing to genetic and environmental conditions

Abstract

From lines selected for high and low frequency of second division segregation (SDS) for asco in linkage group (LG) VI, one wild-type isolate of mating type (mt) a showing extreme SDS-frequency was picked out from the high and the low selection line, respectively. Both wild types were crossed with a strain carrying a met-8 (LG III) and a his-1 (LG V) allele. The met-8′ progeny of mt A was analysed with reference to SDS-frequency for asco. As all crosses were performed in repeats, the influence of environmental conditions could be analysed. No significant influence of the regions surrounding the his-I locus could be established, neither for high, nor for low SDS-frequencies. Environmental conditions significantly influenced the SDS-frequencies of isolates which had a high line background. The isolates with a low line background were less affected in this respect. The SDS-frequencies of isolates with a low line background showed a bimodal-like distribution. This suggests the influence of a major genetic factor. If this is located in any of the LG:s I, III and V, it would not be closely linked to the mt, the met-8 or the his-I locus.