Mutation Effects Of Maize Inbred Lines By Space Flight And Evaluation Of Mutants

Mutation technique by space flight was an effective way to create new germplasm resource and cultivar. In this study, three wide-used maize inbred lines were mutated by space flight. The variation of the main characteristics and mutagenic effects on space conditions of their corresponding progeny lines were analyzed; meanwhile, the genetic variations of SP3 were evaluated with SSR molecular markers. To provide the theoretical basis for the mutant lines'application, morphological and molecular identification were combined to select good mutant line with large genetic differences, and incomplete diallel cross design were used to analyze the combining ability of different characters. The main results of this research were as follows:1. Treated by space flight, the variation range and coefficient of variation of various characters in the SP1 plants of three maize inbred lines were increased, which indicated that space flight mutation could enlarge the variation range of main characters in maize, and broaden the scope of selection. The growth periods were prolonged, plant height,ear height and tassel traits were decreased, ear diameter and kernels per row were increased compared with its CK, but the traits like seeding rate, survived rate, leaf area, ear length were showed in two directions. K305 was the most sensitive one among 3 maize inbred lines against space flight mutation, but the seeding rate and survived rate were too low to severely reduce their breeding efficiency. In comparison, the sensitivity of K169 and 698-3 was weaker.2. Many traits of the lines of mutation offspring SP3 were produced significant variation. And it provided the basis for selecting different types of germplasm materials. In this study, the SP3 plant characters of three maize inbred lines varied toward two directions, but the variance tend to shorter plants and smaller leaf area; it is good for selecting a dwarf and thin leaf mutations. There is little significance for selection because of small ear traits variation. However, the variances of growth period and tassel traits have different comparatively. So, K305 was easy to select out mutations with longer growth period and tassel length and more tassel branch number; K169 tended to select mutations with late-maturing, shorter tassel and more tassel branch number; and 698-3 was prone to select mutations with early maturing and more tassel branch number. Different materials and their different characters had different mutated effects treating by space flight, so it is important to select mutated meterials in the breeding. Otherwise, SSR markers were used to analyze the genetic diversity of the SP3 plants of three maize inbred lines. The results indicated that space flight can make abundant genetic variation, and it is helpful to select variation materials which had real difference with CK.3. Compared with CK, the combining ability analysis of the seven mutations of K305 and eight mutations of 698-3 indicated that the GCA effects of most characters had significant difference. GCA effects of this study characters, four heights, four ear rows, three ear heights, three kernels per row, two ear lengths, one ear diameter and one yield per plant were significantly different with their CK among the seven mutation of K305; besides, plant height showed effects toward two directions, all the performance of ear height showed a negative effect of reducing ear height; ear diameter and rows per ear showed a positive effect; ear length, kernels per row and yield per plant showed bad negative effects. In the eight mutations of 698-3, six kernel weights, six ear diameters, four bald long, four yield per plant, three heights, three kernels per row, two ear heights, and an ear difference were very significant compared with its CK; moreover, yield per plant showed a positive effect, rows per ear showed adverse negative effects, and the remaining characters showed the performance of two-way effect; however, ear diameter, kernels per row and kernel weight tended to show good positive effects, and bald long prefer to show adverse positive effects. That indicated in the same characters of different materials, orientation and size of the GCA effects had widely difference. In addition, the SCA effects of different characters in different mutation of hybrid combinations were quite different with their CK, and some combinations of mutants were better than the original combinations, which manifested mutants might group a more excellent combination. 4. The results showed that with their CK, mutation 1203 of K305 was a good line for high yield breeding, which had very significant GCA effects of ear diameter and ear rows, and a good GCA effect of yield per plant, but it needed a drawf parent to eliminate the high GCA effects of plant height; 1205 and 1217 were drawf lines, which had good GCA effects of plant height and ear height, so they could be applied for drawf, but they need the parents to remove the bad GCA effects of ear length and ear rows, which have good economic traits; mutation 1237 of 698-3 was a good line for high yield breeding, which have good significant effects of yield per plant, ear diameter and 100-kernel weight, but it need a drawf parent to eliminate the high GCA effect of plant height; 1227 had a short plant height, Furthermore, it had good significant GCA effects of yield per plant, ear diameter and 100-kernel weight, Therefor it could be applied on breeding of drawf, and high yield; 1235 could increase the yield of hybrid, which have good significant effects of yield per plant, ear diameter and kernels per row; As the other new inbred lines, each with a distinct identity could be improved and utilized appropriately based on the different breeding objective.