Study On Propagation And Seed Germination Characteristics Of Wild Tobacco Germplasm

The wild tobacco resources are the most important genetic materials for distant hybridization between species, germplasm innovation and the expansion of the genetic background. But in the process of reproduction, the rates of seed setting and germination of wild tobacco are lower than the cultivars. In this study, the typical wild resource N.alata, N.gossei and N.gluca are chose as the objects and the cultivar K326 is chose as the control for this research. Then the morphology, physicochemical index, seed vigor and other aspects of wild tobacco are studied in order to explore the pollen vitality, stigma receptivity, pollen germination, and the germination vigor of seed changes of the endogenous hormone in pistil which has been pollinated. We would like to investigate characteristics of tobacco propagation and seed germination, and provide the material foundation and theoretical basis for the exploitation, utilization and reproductive of the wild species.The results are as follows:(1) The results of pollen vitality and stigma receptivity show : daily variation of these three pollen vigor are bimodal curve which peaks are at 13:00 and 15:00 respectively. Different tobacco resources have their own best period for pollination. As for N.gossei, the time from 1d before flowering to 4d after flowering, is the best period for pollinating. For N.alata, the best period for pollinating is the time of 2-3d after flowering. For K326, the 1d before flowering and the 1d after flowering are the best time to be pollinated.(2) Propagation pattern is different between wild tobacco resource and cultivars. K326 is self-compatible cultivar, and wild tobacco N.alata and N.gossei are facultative xenogamy, but N.alata has poor self-compatibility. The results of pollination indicate: seed setting of wild tobacco is greatly influenced by the space separation of stigma and anther, and lacking of effective pollination mechanism. Furthemore the low rate of seed setting of N.alata is also because of self-incompatibility.(3)The ratio as(IAA+GA3+ZR)/ABA of endogenous phytohormones in pistil is closely related to its affinity after pollination.Compared with K326, the content of N.alata’s IAA, GA3 and ZR are lower, otherwise content of ABA is higher. Pollen germination and the growth of pollen tube have been restrained by significant callose rejection, so the self-compatibility of N.alata is poorer. The(IAA+GA3+ZR)/ABA ratio after outcrossing is higher than that of N.alata after pollination. It shows outcrossing compatibility is better.(4) Compared with K326, the germination vigor wild tobacco seed is poorer. Plant exogenous hormones such as GA3, 6-BA may promote seed germination using suitable concentration. High concentration will inhibit seed germination. The suitable concentration of GA3 is 150-350 mg/L for improving wild tobacco resource’s seed germination activity. The suitable concentration of 6-BA is 5-25mg/L in enhancing the germinative energy and germination percentage, but 6-BA also can inhibit the growth of root and stem.