DNA marking of some quantitative trait loci in the cultivated edible mushroom <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> (Fr.) Kumm.

Fungi of the genus Pleurotus, in particular, species Pleurotus ostreatus (common oyster mushroom) are among most cultivated fungi in the world. Due to intense rates of development of studies in this field, efficient breeding programs are highly required in the search for new P. ostreatus strains. The principal traits used worldwide for selecting strains are intensity of fruitbearing, fruit body cap color (for some consumptive markets), and mycelium growth rate. In this connection, the objective of this work was to study these quantitative traits and to find molecular markers, which could be employed to accomplish breeding programs. In general, we found 12 genomic loci (quantitative trait loci, QTLs) controlling mycelium growth rate of oyster and six QTLs responsible for the fruit body cap color. The genetic map of P. ostreatus was constructed, and all markers of quantitative traits found by us were located on this genetic map. The obtained linkage map can be a useful tool for the accomplishment of breeding programs to improve economically important traits of oyster mushroom.     

Mapping of genomic regions (quantitative trait loci) controlling production and quality in industrial cultures of the edible basidiomycete Pleurotus ostreatus

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.     

Quantitative trait loci controlling vegetative growth rate in the edible basidiomycete Pleurotus ostreatus

Mycelium growth rate is a quantitative characteristic that exhibits continuous variation. This trait has applied interest, as growth rate is correlated with production yield and increased advantage against competitors. In this work, we studied growth rate variation in the edible basidiomycete Pleurotus ostreatus growing as monokaryotic or dikaryotic mycelium on Eger medium or on wheat straw. Our analysis resulted in identification of several genomic regions (quantitative trait loci [QTLs]) involved in the control of growth rate that can be mapped on the genetic linkage map of this fungus. In some cases monokaryotic and dikaryotic QTLs clustered at the same map position, indicating that there are principal genomic areas responsible for growth rate control. The availability of this linkage map of growth rate QTLs can help in the design of rational strain breeding programs based on genomic information.     

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

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.     

Quantitative Trait Loci Controlling Vegetative Growth Rate in the Edible Basidiomycete Pleurotus ostreatus

Mycelium growth rate is a quantitative characteristic that exhibits continuous variation. This trait has applied interest, as growth rate is correlated with production yield and increased advantage against competitors. In this work, we studied growth rate variation in the edible basidiomycete Pleurotus ostreatus growing as monokaryotic or dikaryotic mycelium on Eger medium or on wheat straw. Our analysis resulted in identification of several genomic regions (quantitative trait loci [QTLs]) involved in the control of growth rate that can be mapped on the genetic linkage map of this fungus. In some cases monokaryotic and dikaryotic QTLs clustered at the same map position, indicating that there are principal genomic areas responsible for growth rate control. The availability of this linkage map of growth rate QTLs can help in the design of rational strain breeding programs based on genomic information.     

Isolation, characterization, and expression patterns of a DMC1 homolog from the basidiomycete Pleurotus ostreatus.

Here we describe the isolation of a Pleurotus ostreatus gene PoDMC1. The predicted amino acid sequence of the oyster mushroom gene is 62% identical to the yeast DMC1 and 60% identical to human DMC1. The highest degree of amino acid identity (88%), however, was shown with Coprinus CoLIM15, a DMC1 homolog recently found in Coprinus cinereus. The exact matching of sizes and positions of most introns in both basidiomycete genes underlines the close relationship between these DMC1 orthologs. The RecA homolog DMC1 from yeast and its orthologs from other species have been reported to be meiosis specific and essential for sporulation. Here we show that PoDMC1 is exclusively expressed in the lamellae/basidiospore fraction of fruit bodies and not in somatic cells of fruiting bodies or in vegetative mycelium. Furthermore, the gene is not expressed in the lamellae/basidiospore fraction of a nonsporulating mutant of P. ostreatus. Since one of the major problems in cultivating the oyster mushroom is the abundant sporulation that causes allergic reactions in man, PoDMC1 could be an important target gene in constructing sporeless Pleurotus strains.     

Use of molecular markers for differentiation of cultivated strains of oyster and button mushrooms

Analysis of commercial strains of two edible mushrooms, Pleurotus ostreatus and Agaricus bisporus, using PCR and isozyme electrophoresis techniques allowed us to differentiate groups of genetically similar and distant strains. Among the commercial strains of P. ostreatus, the level of genetic variation was higher suggesting a broader genetic basis employed in breeding of this mushroom. The cultivars and hybrids of, A. bisporus, showed a higher level of homology. The isozyme markers (nonspecific esterase, leucinaminopeptidase, and phosphoglucoisomerase) are recommended for identification of the commercial strains of edible mushrooms.     

Growth promotion of the edible fungus Pleurotus ostreatus by fluorescent pseudomonads

Bacteria were isolated from the mycelial surface of Pleurotus ostreatus and their role in fruiting body induction (fructification) of the edible mushroom P. ostreatus was investigated. Analysis of the bacterial community that colonized the mycelium showed that the species composition and numbers of culturable bacteria differed according to the developmental stage of P. ostreatus. In particular, the population size of fluorescent pseudomonads increased during fruiting body induction. An experiment showed that inoculation of pure cultures of the mycelium with strains of fluorescent Pseudomonas spp. isolated from the mycelial plane of commercially produced mushrooms promoted the formation of primordia and enhanced the development of the basidiome of P. ostreatus. Results of this research strongly suggest that inoculation of the mycelium with specific bacteria may have beneficial applications for mushroom production.     

Molecular tools for breeding basidiomycetes.

The industrial production of edible basidiomycetes is increasing every year as a response to the increasing public demand of them because of their nutritional properties. About a dozen of fungal species can be currently produced for food with sound industrial and economic bases. Notwithstanding, this production is threatened by biotic and abiotic factors that make it necessary to improve the fungal strains currently used in industry. Breeding of edible basidiomycetes, however, has been mainly empirical and slow since the genetic tools useful in the selection of the new genetic material to be introduced in the commercial strains have not been developed for these fungi as it was for other organisms. In this review we will discuss the main genetic factors that should be considered to develop breeding approaches and tools for higher basidiomycetes. These factors are (i) the genetic system controlling fungal mating; (ii) the genomic structure and organisation of these fungi; and (iii) the identification of genes involved in the control of quantitative traits. We will discuss the weight of these factors using the oyster mushroom Pleurotus ostreatus as a model organism for most of the edible fungi cultivated industrially.     

Quantitative trait loci and underlying candidate genes controlling agronomical and fruit quality traits in octoploid strawberry <Emphasis Type="Italic">(Fragaria</Emphasis> × <Emphasis Type="Italic">ananassa</Emphasis>)

Breeding for fruit quality traits in strawberry (Fragaria × ananassa, 2n = 8x = 56) is complex due to the polygenic nature of these traits and the octoploid constitution of this species. In order to improve the efficiency of genotype selection, the identification of quantitative trait loci (QTL) and associated molecular markers will constitute a valuable tool for breeding programs. However, the implementation of these markers in breeding programs depends upon the complexity and stability of QTLs across different environments. In this work, the genetic control of 17 agronomical and fruit quality traits was investigated in strawberry using a F₁ population derived from an intraspecific cross between two contrasting selection lines, ‘232’ and ‘1392’. QTL analyses were performed over three successive years based on the separate parental linkage maps and a pseudo-testcross strategy. The integrated strawberry genetic map consists of 338 molecular markers covering 37 linkage groups, thus exceeding the 28 chromosomes. 33 QTLs were identified for 14 of the 17 studied traits and approximately 37% of them were stable over time. For each trait, 1–5 QTLs were identified with individual effects ranging between 9.2 and 30.5% of the phenotypic variation, indicating that all analysed traits are complex and quantitatively inherited. Many QTLs controlling correlated traits were co-located in homoeology group V, indicating linkage or pleiotropic effects of loci. Candidate genes for several QTLs controlling yield, anthocyanins, firmness and l-ascorbic acid are proposed based on both their co-localization and predicted function. We also report conserved QTLs among strawberry and other Rosaceae based on their syntenic location.     

Efficient construction of high-density linkage map and its application to QTL analysis in barley

Using a High Efficiency Genome Scanning (HEGS) system and recombinant inbred (RI) lines derived from the cross of Russia 6 and H.E.S. 4, a high-density genetic map was constructed in barley. The resulting 1,595.7-cM map encompassed 1,172 loci distributed on the seven linkage groups comprising 1,134 AFLP, 34 SSR, three STS and vrs1 (kernel row type) loci. Including PCR reactions, gel electrophoresis and data processing, 6 months of work by a single person was sufficient for the whole mapping procedure under a reasonable cost. To make an appraisal of the resolution of genetic analysis for the 95 RI lines based on the constructed linkage map, we measured three agronomic traits: plant height, spike exsertion length and 1,000-kernel weight, and the analyzed quantitative trait loci (QTLs) associated with these traits. The results were compared on the number of detected QTLs and their effects between a high-density map and a skeleton map constructed by selected AFLP and anchor markers. The composite interval mapping on the high-density map detected more QTLs than the other analyses. Closely linked markers with QTLs on the high-density map could be powerful tools for marker-assisted selection in barley breeding programs and further genetic analyses including an advanced backcross analysis or a map-based cloning of QTL. Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by J.S. Heslop-Harrison     

Features of lipogenesis of basidiomycetes Pleurotus ostreatus and Flammulina velutipes in cultures on various media

The compositions of free fatty acids (FA) in the mycelia of oyster cap (Pleurotus ostreatus (Jacq. ex Fr.) Kumm.) and honey mushroom (Flammulina velutipes (Curt. ex Fr.) Sing.) and the effect of mycelium cultivation conditions on the composition and proportions of individual FA were investigated. Palmitic and linoleic acids were found to be major acids produced by P. ostreatus growing on solid agar medium and in a submerged culture with a synthetic medium. The composition of minor FA in P. ostreatus was dependent on cultivation conditions. Surface cultivation of its mycelium yielded pentadecanoic, octadecenoic, and stearic acids. Submerged cultivation additionally yielded undecanoic, myristic, hexadecenoic, and lignoceric acids. The composition of free FA in F. velutipes showed no significant differences from that of P. ostreatus. Variation in the C/N ratio in the cultivation medium affected both the FA composition in P. ostreatus and F. velutipes and the relationship between saturated and unsaturated FA.     

Genetic analysis for physical nut traits in almond

Almond breeding is increasingly taking into account kernel quality as a breeding objective. Although information on nut and kernel physical parameters involved in almond quality has already been compiled, the genetic control of these traits has not been studied. This genetic information would improve the efficacy of almond breeding programs. A linkage map with 56 simple-sequence repeat markers was constructed for the “Vivot” × “Blanquerna” almond population showing a wide range of variability for the physical parameters of nut and kernel. A total of 14 putative quantitative trait loci (QTLs) controlling these physical traits were detected in the current study, corresponding to six genomic regions of the eight almond linkage groups (LG). Some QTLs are colocated in the same region or shared the same molecular markers, in a manner that reflects the correlations between the physical traits, as well as with the chemical components of the almond kernel. The limit of detection values for any given trait ranged from 2.06 to 5.17, explaining between 13.0 and 44.0 % of the phenotypic variance of the trait. This new genetic information needs to be taken into account when breeding for physical traits in almond. Increases in the positive quality traits, both physical and chemical, need to be considered simultaneously whenever they are genetically independent, even if they are negatively correlated. This is the first complete genetic framework map for physical components of almond nut and kernel, with 14 putative QTLs associated with a large number of parameters controlling physical traits in almond.     

Mapping quantitative physiological traits in apple (Malus × domestica Borkh.)

Efficient breeding and selection of high-quality apple cultivars requires knowledge and understanding of the underlying genetics. The availability of genetic linkage maps constructed with molecular markers enables the detection and analysis of major genes and quantitative trait loci contributing to the quality traits of a genotype. A segregating population of the cross between the apple varieties `Fiesta' (syn. `Red Pippin') and `Discovery' has been observed over three years at three different sites in Switzerland and data on growth habit, blooming behaviour, juvenile period and fruit quality has been recorded. QTL analyses were performed, based on a genetic linkage map consisting of 804 molecular markers and covering all 17 apple chromosomes. With the maximum likelihood based interval mapping method, the investigated complex traits could be dissected into a number of QTLs affecting the observed characters. Genomic regions participating in the genetic control of stem diameter, plant height increment, leaf size, blooming time, blooming intensity, juvenile phase length, time of fruit maturity, number of fruit, fruit size and weight, fruit flesh firmness, sugar content and fruit acidity were identified and compared with previously mapped QTLs in apple. Although `Discovery' fruit displayed a higher acid content, both acidity QTLs were attributed to the sweeter parent `Fiesta'. This indicated homozygosity at the acidity loci in `Discovery' preventing their detection in the progeny due to the lack of segregation.     

Cultivation of Pleurotus ostreatus on weed plants

Oyster mushroom, Pleurotus ostreatus (Jacq.:Fr.) Kumm. ITCC 3308 (collected from Indian Type Culture Collection, IARI, New Delhi, India, 110012) was grown on dry weed plants, Leonotis sp, Sida acuta, Parthenium argentatum, Ageratum conyzoides, Cassia sophera, Tephrosia purpurea and Lantana camara. Leonotis sp. was the best substrate in fruit body production of P. ostreatus when it was mixed with rice straw (1:1, wet wt/wet wt) for mushroom cultivation. The fruiting time for P. ostreatus was also less on Leonotis sp. than on any other weed substrates tested in the present investigation. T. purpurea was the least suited weed for oyster mushroom cultivation. The main problem of oyster mushroom cultivation on weed substrates was found to be low yield in the second flush that could be overcome by blending weed plants with rice straw. The protein contents of the fruit bodies obtained from Cassia sophera, Parthenium argentatum and Leonotis sp. were not only better than rice straw but also from the rice straw supplemented weeds.     

Regression association analysis of fruit traits with molecular markers in cherries

The use of molecular markers supports the study of genetic marker–trait association of biological and agronomic interest in diverse genetic material. In this research, association between simple sequence repeat (SSR) and random amplified polymorphic DNA (RAPD) markers with fruit traits were investigated in two collections of cherries by applying multiple regression analysis (MRA). Thirty-eight SSR alleles and 135 RAPD fragments were found associated with 14 of affecting fruit traits. Some of SSR and RAPD markers were associated with more than one fruit trait in MRA. Such an association may arise due to pleiotropic effect of the linked quantitative trait locus on different traits. For example, some SSR and RAPD markers were associated with all four traits including fruit cracking, fruit firmness, total soluble solid (TSS) and fruit shape. Also, some markers had correlations with all four characters of TSS, anthocyanin, fruit skin color and fruit flesh color, indicating a significant correlation among these traits. Therefore, it is possible to use these markers along with morphological traits in cherry breeding programs for identification of suitable parents to produce mapping populations and hybrid cultivars. Also, these results could be useful in marker-assisted breeding programs when no other genetic information is available.     

Genetic mapping of yield traits using RIL population derived from Fuchuan Dahuasheng and ICG6375 of peanut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis> L.)

The genetic architecture determinants of yield traits in peanut (Arachis hypogaea L.) are poorly understood. In the present study, an effort was made to map quantitative trait loci (QTLs) for yield traits using recombinant inbred lines (RIL). A genetic linkage map was constructed containing 609 loci, covering a total of 1557.48 cM with an average distance of 2.56 cM between adjacent markers. The present map exhibited good collinearity with the physical map of diploid species of Arachis. Ninety-two repeatable QTLs were identified for 11 traits including height of main stem, total branching number, and nine pod- and seed-related traits. Of the 92 QTLs, 15 QTLs were expressed across three environments and 65 QTLs were newly identified. Twelve QTLs for the height of main stem and the pod- and seed-related traits explaining more than 10 % of phenotypic variation showed a great potential for marker-assisted selection in improving these traits. 相似文献   

Identification of QTL for agronomic traits of importance for olive breeding

Development of methodologies for early selection is one of the most important goals of olive breeding programs at present. In this context, the identification of molecular markers associated with beneficial alleles could allow the development of marker-assisted selection (MAS) strategies in olive breeding programs. Fruit-related and plant vigor traits, which are of key importance for olive selection and breeding, were analyzed during two seasons in a progeny derived from the cross ‘Picual’ × ‘Arbequina.’ Quantitative trait loci (QTL) analyses were performed using MapQTL 4.0. A total of 22 putative QTLs were identified in the map of ‘Arbequina.’ QTLs clustered in linkage groups (LG) 1, 10 and 17. QTLs for oil-related traits located in LG 1 and 10 explained around 20–30 % of the phenotypic variability depending on the season and the trait. QTL for moisture-related traits were detected in LG 1, 10 and 17, and QTLs for the ratio pulp to stone were identified in LG 10 and 17 explaining around 15–20 %. Interaction between QTLs for the same trait was investigated. The significance of these results was discussed considering the co-localization of QTLs and Pearson correlations among traits. Five additional QTLs were detected in the map of ‘Picual.’ Four of them clustered in LG 17 indicating the presence of a QTL for fruit weight explaining around 12.7–15.2 % of the variability. Additionally, a QTL for trunk diameter was detected in LG 14 explaining 16 % of the variation. These results represent an important step toward the application of MAS in olive breeding programs.