Ppd gene effects on frost
Day length (photoperiod) affects plant flowering time. QTL for frost and the time of anthesis and maturity were repeatedly detected on chromosomes 2A, 2B and 2D. The Ppd1_2A allele was tightly linked to the frost QTL on 2A. Remarkably, four out of five frost QTL (next to anthesis QTL) were detected in the proximity of Ppd1_2B in five populations. Due to thePpd1_2B copy number differences between parental lines of these four DH populations, it is likely that the significant frost QTL were contributed by the segregation of Ppd1_2B gene copy numbers, with a high copy number of Ppd1_2B shortening the days to anthesis and inducing early flowering, thus contributing to the frost QTL. Ppd1_2D did not segregate in our six populations and no strong linkage to the frost QTL on 2D was detected.