Advanced Backcross QTL Analysis And Its Application In Genetics And Breeding In Popcorn

Popcorn has irreplaceable utilization in the snack-food industry with its unique popping characteristics.Domestic and foreign breeders have conducted lots of researches in germplasm improvement and genetics. But few researches have been done in the molecular genetics of quantitative character in popcorn. In this paper, 220 BC₂S₁ families developed from a cross between a dent corn inbred, Dan232, and a popcorn inbred, N04, 78 BC₂ testcrosses and two parents were tested with a completely randomized design with two replication in two environments(in spring and in summer) at the Scientific Research and Education Center of Henan Agricultural University, Zhengzhou, Henan in 2004, respectively. Three popping characteristics, 9 ear-kernel, 4 nutritional quality of kernel and 9 plant characters, and 4 developmental stages for BC₂S₁ population were evaluated. 188 markers were selected. QTL were identified for each character, and their genetic effects were estimated using SMM (Single Marker Method) method. The main character performance and the genetic composition for each family were analyzed. The results were as follows:(1) The performance of all BC₂S₁ families were almost the same under two environments with normal distributions. The coefficient of variation was small. There were BC₂S₁ families with higher performance than the popcorn parent for all characters except popping rate in spring, which was 12.27% and 19.09% for expansion fold, 91. 36% and 64. 55% for popping volume, 94.09% and 96.82% for ear-kernel weight, 100.00% and 89.09% for100-kernel weight, more than 18.64% for nutritional quality of kernel, and more than 52. 73% for plant characters.(2) Popcorn parent N04 play the decisive role in popping characteristics. In the BC₂S₁ families genome, homozygous fragments of popcorn parent N04 account for 31.10%～91.60%, heterozygotic fragments of Dan232/N04 account for 7.40%～ 56.20%, homozygous fragments of parent Dan232 account for 0 ～ 9.30%. There main distribution range were 50%-80%, 17.2% -45.7% and 0-5.3%, respectively. For the genotypes of 16 markers in linkage with QTL for popping fold (all from N04), N04/ N04, Dan232/N04 and Dan 232/Dan232 types for a single marker were 60%-95%, 5%-40% and 0, and 71.43%～100%, 0～28.57% and 0 for a single family in the twenty BC₂S₁ lines with the highest popping fold, respectively. While in the twenty BC₂S₁ lines with the lowest popping fold, they were 25%-80%, 20%-75%, 0-5% and 28.57%～85.71%, 14.29%～64.29%, 0～7.14%.(3) 52, 185, 109, 250 and 38 QTLs for 3 popping characteristics,6 ear-kernel...