Breeding Of The Male Sterility Maintainers And Male Sterile Wheat Lines With The Blue Embryo As A Phenotypic Marker

Heterosis is a common phenomenon in biology, and also is one of the most efficient ways to increase yield and improve quality of crops. Heterosis have been widely utilized in lots of field crops (maize, rice, sorghum, oilseed, cotton etc) and vegetable crops (tomato, onion, cucumber, eggplant, cabbage etc) by now, and have achieved great social and economic benefits in the world. Lots of ways to use heterosis in wheat have been put forward and practiced, for instance male sterility by interaction of nuclear and cytoplasm (briefed as three lines system), male sterility by chemical hybridization agent (CHA), nuclear male sterility with two lines and photoperiod or thermo-sensitive male sterility with two lines, etc. some progress have been achieved in wheat heterosis utilization.Nuclear male sterility is one of the most important resources for wheat heterosis utilization. The male sterility of this type is controlled by nuclear genes and there is cytoplasmic effects on agronomic traits, the fertility restoring resources are rich and restoring degrees are higher, recombination with strong heterosis are selected easily. But the limit factor for the utilization of the nuclear male sterility is that there is no efficient maintainer for this kind of male sterility. Focused on this issue, lots of reproduction systems for maintaining the male sterility easily were proposed and examined, such as XYZ system and two lines system, but all those could not be used in wheat production. The maintainer of nuclear male sterility with blue embryo was bred by Huang and it made the possibility for using the nuclear male sterility in wheat heterosis utilization. The mechanism of this system is similar to the XYZ system, with the addition of the phenotypic marker of the blue embryo grains. The disadvantage of this system is that the agronomic traits of the male sterile lines and maintainers is not so good, especially weak seedlings, stunt seedling growth, abnormal spikes, less seed setting, etc, and limits the utilization of this system in wheat heterosis utilization.This study focused on the problems the original nuclear male sterile wheat lines and its maintainers with blue embryo phenotypic marker. Recurrent selection and blue embryo marker were used to improve the nuclear male sterile wheat lines and its maintainers, the easy and efficient ways to breed nuclear male sterile wheat lines and its maintainers with blue embryo marker were also exploited. The main results of this study were as followed: 1. The efficient way to bred nuclear male sterile wheat lines and their maintainers with blue embryo marker is to select the nuclear male sterile lines with the breeding targets from the progeny of multi-recurrent selection (8-10 generations), then to transfer the blue embryo marker into the nuclear male sterile wheat lines selected from the original maintainer with blue embryo. The new bred nuclear male sterile wheat lines and maintainers with blue embryo performed as normal wheat with normal growth characters. The male sterility of the new bred nuclear male sterile wheat lines with blue embryo was stable. The ratio of complete male sterile individuals among the population increased by 10.55%, self seed set rate deceased by 1.4% while compared with the original ones. The new bred maintainer of this male sterile wheat lines is as the original lines in plant height, spike length and floret number, but with self seed set ratio increased by 4.35% in general.2. There were three kinds of efficient ways to bred new nuclear male sterile wheat lines and maintainers with blue embryo. One is the recurrent improvement of the nuclear male sterile wheat lines. The nuclear male sterile wheat lines were improved by recurrent selection and then were crossed with the 4E mono-ploid additional lines to transfer the blue embryo character to it. The nuclear male sterile wheat lines with blue embryo were selected from the segregation population. The advantage of this method was that the agronomic traits of nuclear male sterile wheat lines could be improved simultaneously, and the male sterile wheat lines with different background also could be selected. The second one is improvement of the nuclear male sterile wheat lines and the 4E di-ploid additional lines (with the nuclear male sterile gene) simultaneously. The male sterile lines with white grain and the 4E di-ploid additional lines with dark-blue grain were improved by recurrent selection respectively. Then the two kinds of lines were crossed each other to select the male sterile line with blue grain. The advantage of this method is that the targets to be improved are quite clear and are very efficient to improve single trait. The improved male sterile wheat lines and the 4E di-ploid additional lines are similar in genetic background, the selected individuals with light-blue grain could be directly used as the improved maintainers, and no further selection was needed. The third one is the improvement of the maintainers. Backcross was used to improve the maintainers by backcrossing with the common wheat lines continuously. The advantage of this method is that the method is simple and efficient to a few traits.The above results could provide theriotical and practical base for the improvement of nuclear male sterile wheat lines and their maintainers with blue embryo marker, and also may promote the utilization of this kind male sterile system in wheat heterosis utilization.