Abstract:

In the present study，the relative electric conductivity and logistic equation were used to determine the low semi-lethal temperature（LT50）of ray floret in a segregating chrysanthemum‘Nannong Xuefeng’בMonalisa White’F1 population at full flowering stage，with the intention of investigating genetic variation and QTL for ray florets’cold tolerance. The results showed that LT50 ranged between–8.92 and 1.31 ℃ and distributed normally with a coefficient of variation of 43.60%，indicative of the quantitative nature；in addition，partial maternal inheritance to some extent and transgressive segregations were observed for the cold tolerance of ray florets in the F1 population. Major gene plus polygene inheritance model analysis figured out no major gene for the ray florets’cold tolerance. QTL analysis by the method of composite interval mapping identified six QTLs for ray florets’cold tolerance，harboring on the linkage group X2 and X4 of‘Nannong Xuefeng’map and M2，M11，and M33 of‘Monolisa White’map，with a LOD value of 2.61–3.29. The additive effect of the six QTLs varied in a range of–1.67–1.78 ℃，and the individually explained phenotypic variation ranged from 6.01% to 9.94%，therefore the identified QTLs should be minor genes，confirming the results of major gene plus polygene inheritance model analysis.

Key words: chrysanthemum, ray floret；cold tolerance, genetic variation, QTL mapping