A quantitative trait locus of Agaricus bisporus resistance to Pseudomonas tolaasii is closely linked to natural cap color.

A quantitative trait locus (QTL) of resistance to Pseudomonas tolaasii was detected in Agaricus bisporus using a cross between a wild strain from the Sonoran desert and a cultivated strain. The resistance QTL was strongly linked with the brown color allele of PPC1. This QTL explained about 30% of the variation observed for living bacteria-induced symptoms. The use of bacterial toxin did not reproduce living bacteria symptoms but revealed the same QTL. The latter QTL was not affected by environmental variation. No relation was found between the resistance QTL and the tyrosinase gene, which is involved in the browning process.

Bsn-t alleles from french field strains of agaricus bisporus

In the Agaricus bisporus desert population in California, the dominant Bsn-t allele determines the production of tetrasporic basidia and homokaryotic spores (n) that characterize a heterothallic life cycle. Strains belonging to a French population have the Bsn-b/b genotype that results in bisporic basidia that produce heterokaryotic spores (n + n) which characterize a pseudohomothallic life cycle. More recombination occurs in the tetrasporic population than in the bisporic population. In France, tetrasporic strains are rare. For two such isolates, Bs 261 and Bs 423, we determined the life cycle, the heritability of the tetrasporic trait, the amount of variation in the recombination rate, and the haploid fruiting ability. We found that (i) Bs 261 was heterothallic, (ii) Bs 423 was homokaryotic and homothallic, (iii) Bs 261 was Bsn-t/b, (iv) recombination on a segment of chromosome I depended on the genotype at BSN, (v) some of the homokaryotic offspring of Bs 261 and all of the progeny of Bs 423 were able to fruit, (vi) Bs 261 and Bs 423 were closely related, and (vii) Bs 423 was partially intersterile with other strains of the species.

Conservation of genetic linkage with map expansion in distantly related crosses of Agaricus bisporus.

A previous map of the genome of a hybrid strain which had European parents belonging to the secondarily homothallic fungus Agaricus bisporus var. bisporus appeared to be unusually compact, with a particularly recombophobic segment in the central part of chromosome I. A new map of this segment was constructed based on allelic segregations among 103 homokaryotic offspring of an A. bisporus hybrid between a European parent of the var. bisporus and a Californian parent of the heterothallic var. burnettii. Markers completely linked on the previous map were distributed along 28 cM in the new map. These results suggest that the greater recombination rate could be correlated with the outbreeding behaviour of the var. burnettii.