Study Of Breeding System In Stipagrostis Pennata

The grass Stipagrostis pennata is a good sand-fixating herbage plant in Gurbantongut Desert.The breeding system of Stipagrostis pennata was studied by field observing, SSR and so on.The results are as follow:(1) The relationships between sex expression, pollination mechanism and mating system of Stipagrostis pennata, wind-pollinated species widely in Shihezi ,Xingjiang ,are examined.The anthesis of two sexs is only 5h.Blooming of the first flowers begins at around 09:00 and the last one finishes at around 20:00 every day.Insects pollination does not exist in this area.The flowers of this species are pollinated by itself or wind.Pollen viability is also detected, the result of the highest pollen viability occurs at 15:00-19:00, while another higher peak at 10:00-12:00.The fact that the stigma of Stipagrostis pennata is receptive from 10:00 to 11:00 and from 15:00 to 18:00 reveals that it is morphological protoandy. Receptinity of stigma occurs with the peak of the pollen viability, and connects with the weather, such as temperature, wind and sunshine. The paper had also studied on observation and determination of pollen morphology, vigour ,germination rate , pollination capability of stigma.The results are as follows:â‘ Pollen of S. pennata is lipsoidal breeding, with single germination aperture and granular exospore;â‘¡High germination rate of pollen and strong natural pollination capability of stigma are main factors that it can adopt the environment.(2) Outcrossing rate in an open-pollinated breeding population Stipagrostis pennata was estimated by the co-dominant SSR makers using 1 open-pollinated population.The multilocus outcrossing rate(tm ) was 0.839 and the single-locus outcrossing rate (ts) was 0.661. The multilocus outcrossing rate did not significantly differ from the single-locus outcrossing rate(tm-ts= 0.178).The fixation index (F) was 0.158.The estimates of tm,ts and F utilizing windows version of MLTR program clearly indicate that outcrossing is predominant in the S. pennata open-pollinated breeding population.This is possibly influenced by factors such as plant density, wind power and so on.(3) Clonal structure of 4 populations of Stipagrosits pennata in desert was studied using polypropylenic amine gel electrophoresis, marked by SSR. SSR data at 8 loci indicated high level of clonal diversity in this species with proportion distinguishable variation PD=0.45, from 0.2 to 1. The sizes of diferent clones, however, varied greatly, from 0.2 to 1. The analysis of clonal structure demonstrated that the mosaic among Stipagrosits pennata clones Was clear.The results indicate that Stipagrosits pennata is a typical wind-pollinating plant with high outcrossing rate and has high clone diversity. This paper offered reference basis for the study of sand plants adopting hot and dry desert and the work defending desert.