Selecting Of Drought Resistant Resources And Its Analysis Of Genetic Diversity In Foxtail Millet

Drought stress influences plant growth and severely limits crop productivity world widely. Foxtail millet, with the characteristic of drought resistance, barren endurance and high water use efficiency, is mainly planted in arid and semi-arid regions in Northern China. More recently, following the increased scarcity of water resource and the changing of crop arrangement, studying and enhancing drought resistance of foxtail millet resources is needed. Therefore, in this study we identify the drought resistance at germination period, select drought resistant resources and cluster analysis 120 drought resistant foxtail millet. The results are showed below:1. Study on identification of drought resistance at germination period: Using Polyethylene glycol(PEG)-6000 and mannitol with osmotic potential from -0.25MPa to -1.50MPa for simulating water stress to 10 foxtail millet landraces, the relative germination rate(germination drought resistance index, GDRI) and relative sprout length(RSL) and relative root length(RRL) were served as evaluation indexes, and the osmotica concentration for evaluation of drought resistance in foxtail millet was researched. The result indicated that germination rate of 40 percent of landraces, sprout growth and root growth of 80 percent of varieties were promoted under higher osmotic potential(-0.25MPa～-0.50MPa), and they were inhibited under lower osmotic potential(-0.75MPa～-1.50MPa). Under PEG-6000 or mannitol stress, the correlation was negative between GDRI and 1000-grain weight, and mostly positively moderate between GDRI and relative germinative energy(RGE), and mostly negative between GDRI and the relative root/sprout(RR/S)(under PEG-6000), and lower between GDRI and RSL or RRL; the correlation was mostly positively moderate between RSL and RRL. GDRI and RRL were selected for evaluation indexes; -0.75MPa PEG-6000 or -1.00MPa mannitol stress was proper condition for the evaluation of drought resistance at germination period in foxtail millet.2. Selection of drought resistant resources in foxtail millet: Identification of whole growth period was practiced by using 1200 foxtail millit landraces(lines) from core germplasm and part near cultivars at Urumqi in Xinjiang there the yearly average precipitation is 100 mm, which weae planted in water zone and drought zone, respectively. The 100 resources of drought resistance and 20 resources of no drought resistance were selected. The relative biomass, relative heading date, relative plant height, relative ear diameter, relative seedling height and leaf relative water content were considered as identification indexes of drought resistance in foxtail millit. Thereinto, heading date is straight, and the direct effect acting on the coefficient of drought resistance is bigger(path coefficient is -0.26875), and it is a efficient index in identification of drought resistance. Calculating relative seedling height may be practiced in earlier growth period, and it may be a quick batch screening method, and simple, saving labour and maneuverable than seedling livability under repeated drought. So relative heading date and relative seedling height should be more important in identification of drought resistance in foxtail millit. Also, our results showed that there were very significant effect to heading date under water stress in seedling period, and the yield affected under water stress in seedling period was exhibited by delaying its heading date. Under water stress, the correlation was not necessary or universal between tip-barrenness length and its drought resistance in foxtail millit.3. The analysis of genetic diversity for foxtail millet landraces(lines): The DNA from 120 foxtail millit landraces (lines) were amplified, using 21 SSR primer pairs on 9 chromosomes of foxtail millit. At each locus, the number of alleles varied from 3 to 26, with an average of 14.5. The average polymorphism information content (PIC) was 0.809 , ranging from 0.536 to 0.935; the genetic similarity coefficients for these landraces(lines) varied from 0.8393 to 0.9672, with an average of 0.8906. On the basis of the genetic similarity coefficients, 120 foxtail millit landraces (lines) were divided into 4 groups at genetic similarity coefficient 0.8865, exception for 6 varieties, which have smaller genetic similarity coefficients. The group I was divided into 2 sub-groups: Ii and Iii. The sub-group Ii included 91.5 percent of Loess Altiplano and Inner Mongolia Altiplano landraces (lines); the sub-group Iii included 65 percent of Huabei Plain landraces (lines); the group II included 50 percent of Huabei Plain cultivars; the group III included 62.5 percent of Northwest Inland landraces (lines); the group IV included 5 Inland landraces (lines), which are from wide areas. SSR markers of foxtail millit may indicate the distribution of region and eco-type of foxtail millit. The genetic similarity coefficients of groups(sub-groups) Ii, Iii, II and III were, from small to big, III, Ii, Iii and II, respectively, which showed Huabei Plain cultivars of the near years had the biggest genetic similarity coefficient and their gnetic basis is the narrowest, and so broadening breeding resources is needed there; also, which showed Northwest Inland landraces (lines) had the smallest genetic similarity coefficient and their genetic variation is most; moreover, which showed the genetic similarity coefficient of Loess Altiplano and Inner Mongolia Altiplano landraces (lines) is smaller than one of Huabei Plain landraces (lines) and there is bigger genetic variation than Huabei Plain landraces (lines).