Studies On Pollen Tube Behavior Between Maize And Its Wild Relatives

To find out the crossing barrier between Maize(Zea mays ssp.mats) and its relatives, three corn inbreds,Mo17,B73 and 48-2,were used as the female parents to hybrid with Maize relatives as follows,Zea mays ssp.mexicana,Zea mays ssp.parviglumis,Zea diploperennis,Zea perennis,Coix and Tripsacum.The main results were as follows:1.Pollen grains of Zea mays ssp.mexicana could germinate quickly on the stigmas of Maize(Zea mays ssp.mays).The pollen tubes quickly extended to Maize styles and reached the base of the Maize styles as well as ovary.Moreover,the seed setting rate of Maize×Zea mays ssp.mexicana were very high.There were not significant differences in all these characteristics mentioned above comparing with that of the self-pollinated Maize (CK).It indicated that there was no crossing barrier when Maize was pollinated with Zea mays ssp.mexicana.2.Pollen grains of Zea mays ssp.parviglumis could germinate quickly on the stigmas of Maize.The pollen tubes quickly extended to Maize styles and successfully reached the base of the Maize styles as well as ovary.There was no significant difference in all these characteristics mentioned above comparing with that of the CK.However,the seed setting rate of Maize×Zea mays ssp.parviglumis were lower than that of the CK,and the difference was significant.It indicated that there was partial embryo sac incompatibility in the hybridization of Maize×Zea mays ssp.parviglumis.3.The growth speed of the pollen tubes of Zea diploperennis and Zea perennis on the Maize stigmas were lower than that of Maize themselves respectively.And the seed setting rate of both Maize×Zea diploperennis and Maize×Zea perennis were lower than that of Maize×Maize.The differences mentioned above were significant between outcross Maize and CK.It showed that both the normal fertile hybrids of Maize×Zea diploperennis and Maize×Zeaperennis can be obtained,but to some extent,there were styles incompatibility in the hybridization of Maize×Zea diploperennis as well as Maize×Zea perennis.4.When Maize was hybrided with Tripsacum L.,the pollen grains of Tripsacum L.could germinate quickly on the stigmas of Maize.The pollen tubes quickly extended to the base of the Maize styles and the androgamete were released into embryo sac.Though the hybrids of Maize×Tripsacum can not be obtained,some seed vestige were found on the top of the cobs.It showed that the pollen tubes of Tripsacum L.could extend to the overy of Maize,but the double fertilization cannot be accomplished or the hybrids developed abnormally;the mainly crossing barrier between Maize and Tripsacum L.was embryo sac incompatibility or hybrid death.5.When Maize was hybrided with Coix L.,the pollen grains of Coix L.could germinate quickly,and the pollen tubes quickly reached the base of the Maize styles.But the pollen tubes of Coix L.had not yet extending to the overy of the Maize 24h after pollination.The hybrids of Maize×Coix L.can not be obtianed.It indicated that the crossing barrier between Maize and Coix was the style incompatibility.6.When the same Maize were hybrided with the different Maize relatives,the differences among these combinations were significant in germination rate of pollen grains,percentage of the pollen tubes extending to(the base of) Maize styles and overy,vestige rate and seed setting rate.It indicated that to overcome the crossing barrier between Maize and its relatives and improve their cross-compatibility,the genotype of the Maize using as the female parent should be considered remarkablely.7.When the same Maize were pollinated by different relatives,there were significant differences among these combinations in germination rate of pollen grains,percentage of the pollen tubes extending to(the base of) Maize styles and overy as well as the seed setting rate.And the differences were correlated to the relationship of Maize and its relatives.8.After comparing the abnormal pollen tubes of Maize relatives on the stigmas of Maize to each other,we concluded that the rate of abnormal pollen tubes of Maize relatives was correlated to the relationship of Maize and its relatives.