Localization and characterization of yield component quantitative trait loci (QTLs) in Recombinant Inbred Lines (RILs) of pea, Pisum sativum ssp

The common garden pea (Pisum sativum L.) is the third most agronomically important legume world-wide although it produces varying yields across environment and time. Quantitative trait locus (QTL) mapping can address this issue by providing a minimum number of statistically significant chromosomal regions that contain genes associated with the components of yield. In order to map pea yield QTLs efficiently, a set of 16 novel microsatellite molecular markers was developed and another set of 15 extant markers was characterized more fully. Using the RAMS (Randomly Amplified MicroSatellites) and STMS (Sequence-Tagged Microsatellite Sites) methods, these markers were applied to a set of Recombinant Inbred Line (RIL) peas to complement previously gathered morphological, isozyme and molecular marker data as part of a highly detailed genetic linkage map. Eight independent linkage groups that were consistent with prior studies were established. Each of the 57 RILs, plus the two parental lines, was grown in three greenhouse locations in spring 2006, and in one location in spring 2007. Quantitative trait data related to yield were gathered for each individual. These traits included: days to flowering, first flowering node, number of pods, number of seeds, total seed weight and dry vegetative weight. Two derived traits, average weight per seed and the ratio of seed weight to vegetative weight, were calculated as well. Quantitative data and genetic linkage map data were combined and subsequently analyzed for putative QTLs using Composite Interval Mapping (CIM). Twenty-six QTLs affecting yield components were localized to the linkage maps and characterized for their additive effects. Six reciprocal crosses then were designed from six selected RILs to create hybrid F1 individuals used to: evaluate experimental predictions of the additive effects of the dissected QTLs; improve specific yield traits individually; and combine genetic lines with contrasting values for several yield characters. The identification and characterization of yield component QTLs is the first step towards understanding the molecular basis of naturally occurring genetic variation, and gaining insight into spatial and temporal effects upon yield-related traits in pea.