Preliminary Study on the Fertility Performance of Cucumis Hytivus Chen and Kirkbride and Breeding of Gynoecious Cultivated Lines
|School||Nanjing Agricultural College|
|Keywords||Cucumber Amphidiploid Fertility Cross Compatibility Gynoecious Transfer|
Cucumber (C.sativus L.) is one of the most important vegetable crops all over the world. It is beneficial to cucumber breeding work that researching and utilizing special germplasm resources. The amphidiploid named C.hytivus is the only success of interspecific hybridization and chromosome doubling in the word at present, and by using of it a lot of germplasm materials with wild elite gene have been obtained. The allotriploid derived from amphidiploid x diploid mating, has the potential to become a new type of greenhouse cucumber, as it possesses many good economic traits. But due to the low fertility and compatibility of C. hytivus, it was cross-incompatible and even seedless when amphidiploid x diploid mating, which greatly limited the application of allotriploid. Therefore, it is very important to study the fertility and compatibility of C. hytivus. Besides, the gynoecious cucumber plays an irreplaceable role in cucumber yield breeding and heterosis breeding. Since the inheritance of gynoecious in cucumber was controlled by one dominant gene, and gynoecious was dominant on monoecious, it is realizable to create new gynoecious lines through multi-generation backcrossing.Based on the above research baekground, this paper was focusing on preliminary study of the fertility performance of C.hytivus and creation of gynoecious lines by multi-generation backcross breeding. The details were described as follows:1. Preliminary study on the Fertility of C.hytivusThe fertility characteristics of C. hytivus were preliminarily evaluated by researching the self-cross of each generation, the crossing between C.hytivus and different C.sativus and the pollen viability of S1-S7 of C.hytivus. Results are as follows:There were 4 seeds per fruit of S1, and 1.8 of S2,12.6 of S3,14.3 of S4,14.1 of S7. So it was close to each other between Si and S2, and so was from S3 to S7, while there was obviously increase between S2 and S3. The ratio of fruit with seed was similar between S1 and S2, as well as from from S3 to S7, but there was obviously improving between S2 and S3. Then it could be concluded that the fertility of C.hytivus improves with the generation increasing and the fertility between S1 and S2 is similar, then there is a great enhancement from S2 to S3, and then it tends to be stable after S3. S1 to S3 of C.hytivus were used as maternal parent to make cross with different C.sativus, and the ratio of fruit with seed, the No. of seed per fruit as well as germination ratio of the seeds obtained had not showed consistent change with the generations. This may suggest that the female fertility of C.hytivus is similar among generations. The ratio of dyeable pollen of C.hytivus increased from 11.2% to 49.4% with the increasing generation. So it showed that the pollen viability of C.hytivus increases with generations.2. Preliminary study on the crossing compatibility between C.hytivus and C.sativusThrough reciprocal hybridizations between C.hytivus and C.sativus, it was found that: the rate of seed setting was different between the reciprocal crossings. There were 15 cross combinations which the rate of seed setting higher with C.hytivus as maternal parent, only 2 cross combinations had the higher rate of seed setting with C.sativus as maternal parent. And cross combinations with more than 20 seeds per fruit were all using C.hytivus as maternal parent. The No. of seed per fruit and germination ratio of the seeds obtained were 16.32 and 54.4% respectively in the cross combinations with C.hytivus as maternal parent, while the No. of seed per fruit and germination ratio were 6.22 and 44.64% respectively in the cross combinations with C.sativus as maternal parent. So it can be concluded that the crossing compatible is high with high seed setting ratio when C.hytivus as maternal parent. The result of the cross between C.hytivus and different C.sativus suggested that the crossing compatible was different when the C.sativus crossed with different C.sativus and the following C.sativus showed higher crossing compatible than others:’EC1’,’P01’,’P02’, ’P03’,’627’,’CC4’,’PingWang’,’Hazerd’,’Xishuangbannanesis’,’ChangChunMiCi’, ’CC1’.3. Breeding of gynoecious cucumber lines and related researches.In order to obtain new gynoecious cucumber lines, gynoecious cucumbers such as’EC1’, ’410’were crossed with monoecious ones such as’CC3’,’P01,’P02’,’P03’,’CC1’, ’PingWang’,’627’,’HH1-8-1-2’,’5211’, and selected the gynoecious individual plant to continuously back cross with the monoecious parent for several generations.6 new gynoecious lines were obtained whose gynoecious phenotype are stable. The new gynoecious line is similar with the recurrent parent without several traits. The inheritance character of cucumber sex was also analysed, that the gynoecious trait is controlled by major gene(s), and modified by the minor gene(s).