QTLs for uppermost internode and spike length in two wheat RIL populations and their affect upon plant height at an individual QTL level

Spike length (SL) is one of the most important components of spike morphology, and the uppermost internode represents an ideal organ to study the transportation system. We performed conditional and unconditional quantitative trait locus (QTL) mapping in two unrelated recombinant inbred line populations to precisely detect QTLs for uppermost internode length (UIL) and SL, and to dissect the genetic relationship between these two factors with plant height (PH). Both of the populations were derived from crosses with synthetic wheat. Ten repetitive QTLs for UIL and six environment-independent QTLs for SL were identified in this study, and twelve of these were completely independent of PH. Conditional QTL mapping analysis indicated that SL was more independent to PH than UIL was. The results indicated that the conditional QTL mapping method could evaluate PH component effects on PH, and thus accelerate the selection of suitable loci that improve commercial wheat morphology yet avoid changes to PH.