AFLP mapping of quantitative trait loci influencing seven head-related traits in broccoli (Brassica oleracea var. italica)

Abstract

SummaryThis study identified amplified fragment length polymorphism (AFLP) markers linked to head-related traits in broccoli (Brassica oleracea var. italica) grown in both Winter (W) and Summer (S) in 2008 and in 2009. In total, 227 F2 plants derived from a cross between the heat-tolerant cultivar ‘Shin-Fa 1208’ (SF), and the heat-sensitive cultivar ‘Green Magic’ (GM), were grown in the field. Seven traits including floret height (FH), floret width (FW), head height (HH), head width (HW), head weight (HWT), top weight (TWT), and stem width (SW) were scored. Polymorphic bands were generated by AFLP, and the segregation ratios and distribution of the identified markers over the Brassica genome were compared. Nine linkage groups (LGs), ranging from 75.8 cM to146.5 cM in size, were constructed using 202 informative markers spanning a total of 1,034.5 cM. For the seven traits investigated, 73 quantitative trait loci (QTLs) were dispersed non-randomly in the broccoli genome. Thirty-one unique regions of the genome were detected across the population in Summer trial, and three QTL markers, located on LGs 1, 3, and 5, showed pleiotropic effects on these seven traits. Among these, the QTL linked to the d-64 (S) marker on LG 3 had effects on HH, HWT, and FW, and significant positive correlations existed among these three traits. Thus, the AFLP marker d-64 (S) may have potential for the simultaneous selection of large FW and HH, and increased HWT under high-temperature conditions.