Construction Of A Genetic Map With Molecular Markers And QTL Mapping For Cold Tolerance In Kernel-using Apricot

The kernel-using apricot is a cultivated variety section of economic forest unique to China.The kernel-using apricot breeding started in the 1980s which has made great progress in cultivating excellent varieties through traditional breeding methods.Study in this field has lagged far behind other fruit crops not only in genetic map construction but also in molecular marker-assisted breeding.In this study,two Chinese kernel-using apricot cultivars named’Longwangmao’and’Yaoyi’and 98 hybrids of progeny（F1）were used as a mapping population.The molecular genetic map of kernel-using apricot was successfully constructed by SRAP molecular markers and partial SSR molecular markers,and cold tolerance was also detected.Then,the quantitative characters of cold tolerance for kernel-using apricot were analyzed by quantitative trait locus（QTL）.The results could be used to lay a foundation for positioning,cloning and molecular marker-assisted breeding of cold tolerance in the future.The main results were as follows:1.The F1 generation,as mapping population was constructed by the female parent of’Youyi’derived from Yuxian Area of Hebei Province and the male parent of’Longwangmao’origined from the Zhuolu County of Hebei.A total of 122 hybrids were identified by SRAP markers.And 98 true hybrids were identified from 122 seedlings presenting specific paternal bands of 5 primers of SRAP,which provided a reliable accesion group for the construction of molecular linkage maps and QTL mapping,and so on in the following test.2.The specific 65 pairs selected from 374 SRAP primers and 17 SSR primers were uesed to analyze the F1 generation by polymorphic amplified reaction,and 234 SRAP separated loci and 17 SSR separation loci were detected.Based on the detected loci,a genetic map was constructed and the total of 93 SRAP markers and 17 SSR markers were assigned to 8 linkage groups,with the total length of 884.3 c M,an average distance of 8c M between each markers and the minimum distance of 0.1 c M.Therefore,the linkage map reached the level of middle density and met the need of QTL mapping in the following study.3.The cold tolerance of’Youyi’,’Longwangmao’and 98 individuals were tested.Namely,the shoot percentage of electrolyte leakage was examined under the respectively treatments of 0°C,-10°C,-20°C,-30°C and-40°C and the semi-lethal temperatures(LT₅₀)were calculated using logistic equation.And the QTLs for cold tolerance was detected with software Map QTL 6.0 following Interval Mapping Model.In total of four cold-tolerant QTLs were located on the three linkage groups of LG2,LG3,and LG6.One of them was closely linked to the adjacent marker,and three QTLs were co-segregated with the linkage markers.The results provided a foundation on the breeding of cold-tolerant variety by molecular marker-assisted selection in kernel-using apricot in the future.