| Based on the achieving interspecific hybridization progress aiming at gene introgression from C. hystrix Chakr to C. sativus, the amphidiploid C. hytivus Chen & Kirkbride and its parental C. sativus L. cv. Beijingjietou and wild species C. hystrix et al. were used as core material for further investigation. Novel genotype interspecific hybrids FI, allotriploids and two monosomic alien addition lines have been sucessfully produced in the present study. At the same time, micropropagation system of FI and allotriploid has been established. The development new germplasm were characterized by cytogenetic and molecular - marker analyses.1. Micropropagation and characterization of Cucumis sativus X Cucumis hystrix hybridsFour cucumber cultivars (A309, Erzaozi, Baisitiao and Beijingjietou) were crossed with C. hystrix with different pollination methods. Young embryos were rescued in vitro, and interspecific hybrids were only obtained from the cross between Erzaozi and C. hystrix. The metaphase chromosomes of FI hybrids were counted to be 19. The hybrid was also identified by morphological comparison and electrophoresis of isozyme.The difference in fertility and morphology between the reciprocal plants was found, and the meiosis behaviors in FI were investigated. When cucumber was used as the female parent, both tetraploid and diploid hybrid plants were highly sterile and did not set any fruits. However, When C. hystrix was used as female parent, there were not female flowers in the diploid (2n = 2x = 19) hybrids and the male male flower would be wilt before flowering. In pollen mother cells (PMCs) of the diploid hybrids, the major chromosome configuration was 17 univalents and 1 bivalent at diakinesis and metaphse I (M I). The abnormal meiotic behaviors such as chromosome lagging and spindle misorientation were frequently observed.Apical and axillary buds of hybrids FI, which was obtained through embryo rescuing, were used as explants to establish the micropropagation system. The result indicatied that hybrids F1(dihaploid) proliferated quickly. The proliferation ratio was more than 7.6 on the media with supplemented 0.5 -1.0 mg·L-1 BA only. The multiplication ratio wouldreduced if the concentration was higher than over 1.0 mg·L-1. The shoots would not multiplictate on free plant growth regulator media.2. An allotriploid derived from a amphidiploid X diploid mating in Cucumis : production, micropropagation and verificationA fully fertile interspecific hybrid (Cucumis hytivus Chen and Kirkbride, 2n = 4x = 38) between Cucumis hystrix Chakr. (2n = 2x = 24) and C. sativus L. (2n = 2x - 14) was previously produced by means of FI (2n =19) embryo rescue and subsequent chromosome doubling. This amphidiploid, a new synthetic species, may serve as a genetic bridge in Cucumis, and thus is a source for broadening the genetic base of C. sativus. The identification and characterization of fertile progeny possessing lower ploidy levels would facilitate bridge among Cucumis species. Putative allotriploids (2n = 26) were recovered from C. hytivus X C. sativus matings by means of embryo culture. Experiments were designed to confirm their genetic constitution, describe their morphology, and establish an efficient protocol for their micropropagation. Apical and axillary buds of these putative allotriploid plants were used as explants to establish a micropropagation system for subsequent verification and characterization of ploidy. Of the array of micropropagation media tested, the most effective for the induction of adventitious buds (desginated Stage II) was a Murashige and Skoog (MS) growth media containing 3.0 mg· L-1 BA + 0.2 mg · L-1 NAA or containing 2.2 mg · L-1 BA only. The mean number of adventitious buds per explant in the two media was 6.8 and 6.5, respectively. Shoots resulting from adventitious buds produced roots (Stage III) in relative abundance (39 of 42, 92.8%) on half-strength MS medium containing 0.2 mg · L-1 IBA. The survivorship of rooted plantlets after acclimatization as assessed... |
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