Mapping of Genomic Regions (Quantitative Trait Loci) Controlling Production and Quality in Industrial Cultures of the Edible Basidiomycete Pleurotus ostreatus

Abstract

Industrial production of the edible basidiomycete Pleurotus ostreatus (oyster mushroom) is based on a solid fermentation process in which a limited number of selected strains are used. Optimization of industrial mushroom production depends on improving the culture process and breeding new strains with higher yields and productivities. Traditionally, fungal breeding has been carried out by an empirical trial and error process. In this study, we used a different approach by mapping quantitative trait loci (QTLs) controlling culture production and quality within the framework of the genetic linkage map of P. ostreatus. Ten production traits and four quality traits were studied and mapped. The production QTLs identified explain nearly one-half of the production variation. More interestingly, a single QTL mapping to the highly polymorphic chromosome VII appears to be involved in control of all the productivity traits studied. Quality QTLs appear to be scattered across the genome and to have less effect on the variation of the corresponding traits. Moreover, some of the new hybrid strains constructed in the course of our experiments had production or quality values higher than those of the parents or other commercial strains. This approach opens the possibility of marker-assisted selection and breeding of new industrial strains of this fungus.The edible mushroom production industry is more important every year for several reasons: mushrooms are an efficient low-fat protein source, they may be cultivated on a wide variety of substrates, and they have many industrial and medical applications. The oyster mushroom (Pleurotus ostreatus Jacq. ex Fr Kummer) is the second largest edible mushroom crop behind the white button mushroom, Agaricus bisporus, and it accounts for nearly one-quarter of the total worldwide mushroom production (4, 5). This fungus is also a source of enzymes and other products with industrial and medical applications (6,11,12,23), and it can be used as a decontaminating agent (3) and as an organic fertilizer (1).Industrial production of P. ostreatus is based on a two-step solid fermentation process. In the first step, the mycelium colonizes a wheat (or cereal) straw-based substrate under lightand oxygen-limited conditions at an incubation temperature of 24°C. This process takes between 1 and 2 weeks before the mycelium reaches the substrate surface. At this time, the incubation conditions are changed (12-h photoperiod, forced ventilation) to induce successive flushes of mushroom fruiting. The fruiting temperature depends on the strain and varies between 15°C (P. ostreatus var. ostreatus) and 21°C (P. ostreatus var. florida).Optimization of P. ostreatus industrial fermentation is based primarily on process improvement and strain improvement. Whereas much work has been done on process improvement (27), few systematic studies of genetic breeding of P. ostreatus strains have been reported. This is also true for other industrially cultured mushrooms.Understanding mushroom breeding systems is a major landmark ...

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

“…We also observed that the earliest hybrids tended to produce a higher number of smaller mushrooms, as already underlined by Xu (38), with production spread throughout the whole cropping period. Similar relationships between these productive traits have been described in another edible mushroom, P. ostreatus (15). This variability in earliness could be useful in developing new hybrid strains that cover the range of commercial mushroom outlets.…”

“…If numerous QTL analyses related to life history traits have been reported for various fungi (4,(17)(18)(19)34), those concerning yield-related traits in edible mushrooms are scarcer. In the oyster mushroom, Pleurotus oestratus, QTL controlling the growth rate, biomass production, and several production traits have been described (15,16,29). Although the button mushroom, Agaricus bisporus (Lange) Imbach, is the most widely cultivated edible mushroom species in Europe and North America (28), little is known about the genetic bases of important agronomic traits.…”

The effect of the interaction of various spawn grains with different culture medium on carpophore dry weights and stipe and pileus diameters of Lentinus squarrosulus (Mont.) Singer

“…depends on improving the culture process (Larraya et al, 2003). There are various additives that are known to stimulate fruiting.…”

Genetic map of a basidiomycete fungus, Lentinula edodes (shiitake mushroom), constructed by tetrad analysis

“…Kwan and Xu (2002) employed quantitative trait locus (QTL) analysis to examine the growth rate of monokaryotic strains. Agronomic traits have also been characterized by QTL analysis in other edible basidiomycetes, Agaricus bisporus and Pleurotus ostreatus (Moquet et al 1999, Larraya et al 2002, 2003.…”