Diversity In Rice Populations Research Articles

Genome-wide association study of agronomic traits in rice cultivated in temperate regions

BackgroundRice plants are sensitive to the agro-climate conditions, being photoperiod one of main factor contributing to their adaptation to the region where they are grown. Dissecting the genetic bases underlying diversity in rice populations adapted to specific environmental conditions is a fundamental resource for breeding. In this study we have analysed a collection of japonica varieties adapted to temperate regions to perform association studies with traits of high agronomical interest such as heading date, plant height, number of panicles, panicle length and number of grains per panicle.ResultsWe have performed a genome wide association study using a panel of 1713 SNPs that, based on previous linkage disequilibrium estimations, provides a full coverage of the whole genome. We have found a total of 43 SNPs associated with variations in the different traits. The identified SNPs were distributed across the genome except in chromosome 12, where no associated SNPs were found. The inspection of the vicinity of these markers also revealed a set of genes associated with physiological functions strongly linked to agronomic traits. Of special relevance are two genes involved in gibberellin homeostasis that are associated with plant height and panicle length. We also detected novel associated sites with heading date, panicle length and number of grain per panicle.ConclusionWe have identified loci associated with important agronomic traits among cultivars adapted to temperate conditions. Some of these markers co-localized with already known genes or QTLs, but the association also provided novel molecular markers that can be of help to elucidate the complicated genetic mechanism controlling important agronomic traits, as flowering regulation in the non-dependent photoperiod pathway. The detected associated markers may provide important tools for the genetic improvement of rice cultivars in temperate regions.

Genetic diversity in rice populations of Nigeria: Influence of community structure

Two rice species, Oryza glaberrima and O. sativa, are often mix-planted in West Africa, and their populations, particulary those of O. glaberrima, are highly polymorphic in seed type. It was found that the seed-type diversity within glaberrima populations, as shown by the “amount of information”, H = − Σp i log e p i , was correlated with species diversity in the field (also shown by H), and gave a curvillinear regression on the proportion of glaberrima plants to the total number of rice plants. The highest diversity occurred when the proportion was 50–60%. A similar trend was also found for sativa populations. The background and significance of this phenomenon are briefly discussed.