Studies On The Seedless Mechanism And Regulation Of Shatianyou (Citrus Grandis Osbeck)

Shat i anyou (Ci trus grandis Osbeck), a famous subtropical fruit in our country, was enjoyed by consumers all over the world because of its super economical characters, such as full flavour and strong storability. However, its commercial value and competitive ability in the international market were affected by excessive seeds. Therefore, studies on the seedless mechanism and regulation have important significance for the production of Shatianyou.l.Jishou Shatianyou, a seedless pummelo, was used as material to investigate its quality and seedless causation by treating with pollen isolation, natural and artificial pollination based on the examination and analysis of its sexual organs. The results showed that the average seed number per fruit ranged from 2 to 33. Its male and female organs were fertile. Abortion of most embryos was considered as the causation of the seedlessness. With the fruit coat becoming lighter, the edible section increased, while the average weight per fruit, contents of sugar and soluble solids decreased. The results provide referential bases for exploring and utilizing variety resources of seedless pummelo.2. In order to prove fructuation mechanism of seedless Shatian pummelo, Jishou seedless Shatian pummelo and its parent cultivars were used as materials for endogenous hormonal analysis. The results are as follows: Similar to common seedy Shatian pummelo, the content of growth promoting substances in ovaries, such as endogenous IAA^ GA3v CTKS, were increased by the treatment of pollination. The increasing range of the growth promoting substances under the treatment of cross-pollination was bigger than that under the treatment of self-pollination. The content of ABA also increased. But the decreasing speed of the cross-pollination treatment was slower than that of self-pollination treatment, the endogenous promotive hormone contents in non-pollinated ovary kept in a low level, While ABA content increased. The change patterns of endogenous hormones were different between young fruits of seedless Shatian pummelo and common seedy Shatian pummelo during 49~56d after pollination. During this period, the levels of endogenous It\.t\.^ GA3> CTKS in young fruits of seedless Shatian pummelo were decreased, while ABA content increased. That is the reasonwhy the fructuation rate of seedless Shatian pummelo was lower than that of common seedy Shatian puramelo. But the endogenous IAA was still kept in a higher level and ABA was kept in lower level. The fruit abscission was not serious, although it has fewer seeds.3. Using common adult shatian pummelo as materials, the effects on fruit quality and parthenocarpy of plant growth regulators were studied. IAA+GA4+7+6-BA solution was sprayed before flowering and 7d after flowering, and the Hongrang pummelo-pollination was considered as the control(CK). The results showed that plant growth regulator at appropriate phase can successfully induce the parthenocarpy; the quality of seedless fruits is similar to that of the control, the fruit peel became lighter, the rate of edible section increased. But the rate of fructuation is lower and the fruit weight is reduced. Treatments of IAA 150mg/L+ GA4+- 100mg/L+6-BA lOOmg/L and IAA 150mg/L+ GA4,- 150mg/L+6-BA lOOmg/L were found to be better than others.