Microspore Dedifferentiation In Eggplant Genotypes And Its Related Factors

Eggplant (Solanum melongina L.) is an important vegetable species. Microspore culture technology effectively create valuable breeding materials. In eggplants, application of this technology, however, does not achieve this goal successfully. The microsporal dedifferentiation and embryogenesis is not stable and the processes may stop at a developmental stage. It is thus necessary to investigate the underlining mechanisms.In the present work, seven genotypes at different cultivation conditions were used. Eggplant flower bud morphology and anatomy, microspore culture, endogenous hormones contents in anthers and HSP70 expression were analyzed to reveal the effects of genotype, temperature, culture condition at cellular, physiological and gene levels.1. In greenhouse and open field cultivation conditions, the index of flower bud morphology and anatomy showed certain diversity, such as the length of flower bud of the plants in greenhouse is longer than that in open field. It was noticed that at different cultivation conditions, the uni-nucleate microspore late stage was at the morphological stage in which the distance between the top edges of petal and sepal kept at a 0-2 mm range.2. There existed significant differences among eggplant genotypes during microsporal dedifferentiation and embryogenesis in vitro. Heat shock at 36℃enhanced dedifferentiation in genotypes Z1-Z3, which was classified as dedifferentiation type (DD Type), and show enlarged microspore-a sign of dedifferentiation, with embryoid formation in genotype Z3. In genotypes Z4-Z7, however, microspore did not enlarge, and no embryoid produced in the given culture conditions, and those genotypes were classified as non-dedifferentiation type (ND Type).3. Endogenous hormones, IAA, GA3, ABA and ZR were measured in the freshly collected anthers at late uni-nucleate microspore stage. The DD genotype anthers showed much higher IAA, GA3 and ABA levels but lower ZR level than that in the ND genotypes. Thus, there existed a clear and ordered difference between the DD and ND Types.During a low temperature (4℃) treatment, significant differences again occurred between the DD and ND types.IAA, GA3 and ABA contents increased in the ND genotypes, in contrast, the DD genotypes did not show such an increase.Compared with the effects of heat shock treatments at 25℃/6 d,36℃higher temperature shock in most cases lead to even lowered IAA,ABA levels than those of the low temperature treatment in both DD and ND Types.4. The results of realtime-PCR in Z1-Z3 eggplant anthers indicated that a heat shock at 36℃for 6 days caused HSP70 mRNA expression. It was noticed that in all the 3 genotype anthers during the temperature changes, the HSP70 expression was not constant.