Quantitative Trait Locus Mapping of Yield-Related Components and Oligogenic Control of the Cap Color of the Button Mushroom, Agaricus bisporus

Abstract

bAs in other crops, yield is an important trait to be selected for in edible mushrooms, but its inheritance is poorly understood. Therefore, we have investigated the complex genetic architecture of yield-related traits in Agaricus bisporus through the mapping of quantitative trait loci (QTL), using second-generation hybrid progeny derived from a cross between a wild strain and a commercial cultivar. Yield, average weight per mushroom, number of fruiting bodies per m 2 , earliness, and cap color were evaluated in two independent experiments. A total of 23 QTL were detected for 7 yield-related traits. These QTL together explained between 21% (two-flushes yield) and 59% (earliness) of the phenotypic variation. Fifteen QTL (65%) were consistent between the two experiments. Four regions underlying significant QTL controlling yield, average weight, and number were detected on linkage groups II, III, IV, and X, suggesting a pleiotropic effect or tight linkage. Up to six QTL were identified for earliness. The PPC1 locus, together with two additional genomic regions, explained up to 90% of the phenotypic variation of the cap color. Alleles from the wild parent showed beneficial effects for some yield traits, suggesting that the wild germ plasm is a valuable source of variation for several agronomic traits. Our results constitute a key step toward marker-assisted selection and provide a solid foundation to go further into the biological mechanisms controlling productive traits in the button mushroom.

Relationship between Yield Components and Partial Resistance to Lecanicillium fungicola in the Button Mushroom, Agaricus bisporus, Assessed by Quantitative Trait Locus Mapping

“…The QTL with overlapping LOD-1 support intervals were assumed to be a single QTL if they belonged to the same trait and to be linked or pleiotropic if they represented different traits. Likewise, the colocations between the QTL described here and QTL detected for other crop production traits (9) were also assessed by comparing confidence interval (CI) positions. The probability that QTL colocations occurred by chance was calculated according to the method of Patterson (22), using the hypergeometric probability distribution function, as follows:…”

“…The process of QTL detection is fully described in the companion paper (9). In brief, QTL analyses were based on the genetic linkage map developed by Foulongne-Oriol et al (10) and were carried out using the composite interval mapping (CIM) module implemented in the QTL Cartographer software (2).…”

“…The use of wild germ plasm as a source of resistance to disease in crossbreeding may reduce agronomic fitness and hamper genetic progress due to unfavorable traits. Thus, we also analyzed the relationships between the QTL of resistance to dry bubble found here and those related to other crop production traits described in the companion paper (9). Consequences for breeding management and opportunities for marker-assisted selection in the button mushroom are discussed.…”

“…The R 2 value of each QTL and the parental allele that contributes to the resistance are given at the top and bottom of the confidence intervals, respectively. Gray segments delimited on some linkage groups correspond to QTL for yield-related traits described in the companion paper (9).…”

“…QTL for various yield-related traits (J1, earliness; Y, yield; N, number of mushrooms per m 2 ; W, average weight per mushroom) and cap color parameters (L, lightness) are described in the companion paper (9). Five overlapping genomic regions controlling both dry-bubble resistance (this study) and the above-mentioned crop production traits were highlighted by comparative mapping (Fig.…”