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Abstract Background Grain endosperm chalkiness of rice is a varietal characteristic that negatively affects not only the appearance and milling properties but also the cooking texture and palatability of cooked rice. However, grain chalkiness is a complex quantitative genetic trait and the molecular mechanisms underlying its formation are poorly understood. Results A near-isogenic line CSSL50-1 with high chalkiness was compared with its normal parental line Asominori for grain endosperm chalkiness. Physico-biochemical analyses of ripened grains showed that, compared with Asominori, CSSL50-1 contains higher levels of amylose and 8 DP (degree of polymerization) short-chain amylopectin, but lower medium length 12 DP amylopectin. Transcriptome analysis of 15 DAF (day after flowering) caryopses of the isogenic lines identified 623 differential expressed genes (P < 0.01), among which 324 genes are up-regulated and 299 down-regulated. These genes were classified into 18 major categories, with 65.3% of them belong to six major functional groups: signal transduction, cell rescue/defense, transcription, protein degradation, carbohydrate metabolism and redox homeostasis. Detailed pathway dissection demonstrated that genes involved in sucrose and starch synthesis are up-regulated, whereas those involved in non-starch polysaccharides are down regulated. Several genes involved in oxidoreductive homeostasis were found to have higher expression levels in CSSL50-1 as well, suggesting potential roles of ROS in grain chalkiness formation. Conclusion Extensive gene expression changes were detected during rice grain chalkiness formation. Over half of these differentially expressed genes are implicated in several important categories of genes, including signal transduction, transcription, carbohydrate metabolism and redox homeostasis, suggesting that chalkiness formation involves multiple metabolic and regulatory pathways.

Fat content (FC) is an important component of the nutritional quality of the rice (Oryza sativa L.) grain and a partial determinant of grain quality. Three FC QTLs were identified from an analysis of a set of rice 'Kasalath'/'Koshihikari' backcross inbred lines, which were grown in three independent environments. Two of these QTLs (qFC7.1 and qFC7.2) were located on chromosome 7, and they were detected in all three environments. The presence of qFC7.1 and qFC7.2 was further confirmed by testing a set of 'Kasalath' (donor) / 'Koshihikari' (recipient) chromosome segment substitution lines (CSSLs) across six environments. Both QTLs significantly increased grain FC and they might be involved in lipid metabolism. The two QTLs were stably expressed in a number of environments and populations, making them suitable candidates for the improvement of FC via marker assisted breeding. Key words: rice (Oryza sativa L.), fat content, protein content, QTL mapping. Le teneur en lipides (FC pour << fat content >>) est une composante importante de la qualite nutritionnelle du grain de riz (Oryza sativa L.) et determine en partie la qualite du grain. Trois QTL pour le FC ont ete identifies au terme de l'analyse d'une serie de lignees retrocroisees 'Kasalath'/'Koshihikari', lesquelles ont ete cultivees dans trois environnements independants. Deux de ces QTL (qFC7,1 et qFC7,2) sont situes sur le chromosome 7 et ont ete detectes dans les trois environnements. La presence de qFC7,1 et qFC7,2 a ete confirmee au sein de lignees de substitution pour des segments chromosomiques (CSSL) issues du croisement 'Kasalath' (donneur) / 'Koshihikari' (receveur), lesquelles ont ete cultivees dans six environnements. Les deux QTL contribuaient a augmenter significativement la teneur en lipides et l'emplacement genomique de qFC7,2 suggere que celui-ci serait implique dans le metabolisme des lipides. Les deux QTL ont ete exprimes de maniere stable au sein de plusieurs environnements et populations, ce qui en fait des candidats attrayants pour l' amelioration de la teneur en lipides par selection assistee de marqueurs. Mots-cles : riz (Oryza sativa L.), teneur en lipides, teneur en proteines, cartographie QTL. [Traduit par la Redaction], Introduction The fat fraction of the rice (Oryza sativa L.) grain, which is composed mainly of triacylglycerols, is largely concentrated in the embryo and the aleurone. Its biological function is [...]

Heat stress is one of the major abiotic stresses that adversely affect growth and yield inLentinula edodes(Shiitake mushroom) under natural cultivation. In this study, two parental strains (L808 and Lsm9), an F1strain, and an F2population derived from their hybrid progeny were used to evaluate the regeneration of mycelia after heat stress. A multi-level heat stress experiment showed that the dynamics of radial mycelium expansion of the two parents followed a linear equation after heat stress treatment at 37°C for 4–24 h, 42°C for 4–16 h, or 45°C for 4 h. Three indices were selected to describe the regeneration ability of the strains, including the number of regeneration days (NRD), the real growth rate after heat stress (Vregeneration), and the regenerative index (RI). L808 presented a faster rate of regeneration, while Lsm9 had better regeneration quality. The phenotype analysis of the F2population showed that these indices were controlled by multiple genetic factors with high heritability. Four strains were selected from the population, pyramiding the advantages of heat resistance from the two parents. The results will help our understanding of the genetic features of this mushroom after extreme high-temperature stress. [ABSTRACT FROM PUBLISHER]