Analysis Of Breeding Systems And Hybrids’ Inheritance Of Gazania Rigens L.

Gazania rigens L. as test material, we discuss their F1 hybrid breeding system and genetic diversity. The main research directions are Gazania insect pollination mechanism, integrated features floral, breeding system type, pollen viability, reproductive resource allocation and other features in the natural environment. At the same time we use the application of major gene and polygene mixed inheritance model of quantitative trait in a single generation segregation analysis as research method to make genetic analysis of their F1 hybrid populations’ floral and leaf traits. The main findings are as follows:(1) Under the conditions of experiment, it was observed that mainly pollinators of Gazania were 9 species, belonging to 6 families, 3 orders. They were Lepidoptera: Lycaenidae, Nymphalidae, Hesperiidae, Pieridae; Hymenoptera: Apidae; and Diptera: Syrphidae. Butterflies and bees played a larger role in the cross-pollination on Gazania. In natural communities, visited frequency per flower was 9.1 times/h, and visiting frequency of insects was 3.51 flowers/min. The flight distance of pollinator insects in flowers appeared skewed distribution, the average flight distance was 1.01 m/time, and the short flight less than 1m occupied 60% in the total number of flights. The flights less than 1 m of the bees occupied 80.5% in the total number of observation times, manifesting as rapid pollination within a small range, while butterflies was more relevant to pollination on a wide range.(2) The test results of artificial pollination showed the low self-compatibility of Gazania, which ripening rate of geitonogamy was less than 1%. The outcrossing index(OCI) of Gazania was 4, and the P/O ratios for 4 text breeds were between 2108.0 and 195525.0, where the highest P/O ratio was 6025 for ’Chinese Gazania’, and the lowest was 4084 for ’Su 1’, belonging to breeding system of obligate outcrossing.(3) The test results of vitro pollen-germination showed that the medium with 100 g.L-1-150 g.L-1 PEG4000+150g.L-1 sucrose+100mg.L-1 boric acid+300mg.L-1 Ca2+ was more appropriate. It could significantly promote pollen germination that adding a certain concentration of sucrose to polyethylene glycol(PEG), while it had no effect on that adding boric acid and Ca2+.(4) Pollen vigor changed with flowering time. Daily flowering process had little effect on pollen vigor, which tubular flowers flowering day by day maintained at a steady state. Pollen vigor appeared a highly significant negative correlation with the time after spreading, which pollen vigor maintained a higher level in 4h after anthers spreading pollens, reaching to 44.83%-49.09%, and which sharply declined after 24 h and almost lost vitality after 72 h. Bagging in artificial hybridization could improve pollen vigor of Gazania. It was more obviously seen in a low temperature environment.(5) There was allometric relationship between plant size and resource allocation of the breeding in florescence. It appeared a significant positive correlation between reproductive investment and individual size, and a non-significant negative correlation between reproductive allocation and the size. The allometric relationship between individual size and the sex distribution in florescence did not meet the prediction of SDS theory, which there was no trade-off between individual size and sex distribution, but which existed trade-offs between bisexual investment on single flower, suggesting that the competition of female and male function of Gazania for repository might take place mainly on the flower level. The biomass of attract structure(petals) was closely related to the male investment. The P/O ratio of single ’white star’ or ’red kiss’ appeared positive correlation with individual size.(6) In the hybrid F1 of Gazania groups, the 7 traits studied all appeared separation in different degrees and transgressive individual, which coefficient of variation was 10.75%-28.74%. In addition to leaf length/width and the number of tubular flowers, other traits showed a significant negative mid-parent heterosis, which traits, such as leaf width, flower diameter, inflorescence diameter and number of ray florets, appeared negative low-parent heterosis.(7) In the study of single generation of separation and analysis in the genetic model mixing the major genes and the polygene in plant quantitative traits, it was found that leaf width and tubular flowers had accorded with the model A-0, which there was no major gene, or which was controlled by multiple genes. The leaf length, leaf length/width and inflorescence diameter accorded with model A-1, and were controlled by a pair of major genes. It represented additive effects and dominant effects at the same time between alleles, where additive effect appeared positive synergy, and where dominant effect manifested as negative effect. The major gene heritability of the leaf length/width and the inflorescence diameter respectively were 50.59% and 54.79%.(8) Analyzed the genetic progress of the three traits(controlled by the major genes), it showed that with increasing selection rate in hybrid F1, the absolute genetic progress(△G) and the relative genetic progress(△G′)of the three traits both trended downward. It could be seen that in the groups of larger variation range, selecting the individual with the longest inflorescence diameter at the rate of 10% as breeding parents, it could obtain the progenies with relatively higher genetic progress(more than 20%). It is comparatively ideal that selection rate of leaf length/width was within the 1-10%, and the rate of leaf length should be controlled within 5%. This result provided a theoretical basis for parent apolegamy of crossbreeding in Gazania.