Evidence of epistatic suppression of repeat fruiting in cultivated strawberry.

BACKGROUND: Consumers purchase fresh strawberries all year long. Extending the fruiting season for new strawberry cultivars is a common breeding goal. Understanding the inheritance of repeat fruiting is key to improving breeding efficiency. Several independent research groups using multiple genotypes and analytic approaches have all identified a single genomic region in strawberry associated with repeat fruiting. Markers mapped to this region were used to evaluate breeding parents from the United States Department of Agriculture - Agricultural Research Service (USDA-ARS) strawberry breeding program at Beltsville, Maryland. RESULTS: Markers mapped to repeat fruiting identified once-fruiting genotypes but not repeat-fruiting genotypes. Eleven of twenty-three breeding parents with repeat-fruiting marker profiles were actually once fruiting, indicating at least one additional locus acting epistatically to suppress repeat fruiting. Family segregation ratios could not be predicted reliably by the combined use of parental phenotypes and marker profiles, when using a single-gene model. Expected segregation ratios were calculated for all phenotypic and marker-profile combinations possible from the mapped locus combined with a hypothetical dominant or recessive suppressor locus. Segregation ratios specific to an epistatic suppressor acting on the mapped locus were observed in four families. The segregation ratios for two families were best explained by a dominant suppressor acting on the mapped locus, and, for the other two, by a recessive suppressor. Not all of the observed ratios could be explained by one model or the other, and when multiple families with a common parent were compared, there was no predicted genotype for the common parent that would lead to all of the observed segregation ratios. CONCLUSIONS: Considering all lines of evidence in this study and others, repeat-fruiting in commercial strawberry is controlled primarily by a dominant allele at a single locus, previously mapped by multiple groups. At least two additional genes, one dominant and one recessive, exist that act epistatically to suppress repeat fruiting. Environmental effects and/or incomplete penetrance likely affect phenotype through the suppressor loci, rather than the primary mapped locus. One of the dominant suppressors acts only in the first year, the year the plant is germinated from seed, and not after the plant has experienced a winter.

Selection of reference genes in Hedysarum coronarium under various stresses and stages of development.

The cultivation of Hedysarum coronarium has generated interest recently for its high yield as a fodder crop, its high protein content, and the presence of condensed tannins in its leaf and stem tissues. Gene expression studies can lead to a better understanding of the biological processes of live organisms. Specifically, reverse transcription followed by quantitative polymerase chain reaction (PCR) represents the most powerful technology for comparing the expression profiles of target genes. The use of reference genes as internal controls to normalize messenger RNA (mRNA) levels is a requirement of quantitative PCR (qPCR). Few studies on reference genes have been performed in plants, and no studies have been performed in H. coronarium. Therefore, the aim of this study was to identify and evaluate reference genes to use in qPCR in H. coronarium. Sulla tissues under two conditions of abiotic stress and at various stages of development were studied to determine adequate reference genes. To optimize the identity and number of reference genes, geNorm and BestKeeper software programs were employed. Based on the results of both analyses, TUA1, TUA2, and UBQ were found to be the most suitable reference genes, and the combination of these three genes was suggested for the accurate normalization of gene expression in sulla tissues.

Selection of housekeeping genes for normalization by real-time RT-PCR: analysis of Or-MYB1 gene expression in Orobanche ramosa development.

Real-time PCR has become the method of choice for accurate and in-depth expression studies of candidate genes. To avoid bias, real-time PCR is referred to one or several internal control genes that should not fluctuate among treatments. A need for reference genes in the parasitic plant Orobanche ramosa has emerged, and the studies in this area have not yet been evaluated. In this study, the genes 18S rRNA, Or-act1, Or-tub1, and Or-ubq1 were compared in terms of expression stability using the BestKeeper software program. Among the four common endogenous control genes, Or-act1 and Or-ubq1 were the most stable in O. ramosa samples. In parallel, a study was carried out studying the expression of the transcription factor Or-MYB1 that seemed to be implicated during preinfection stages. The normalization strategy presented here is a prerequisite to accurate real-time PCR expression profiling that, among other things, opens up the possibility of studying messenger RNA levels of low-copy-number-like transcription factors.