Screening Of Germplasm Pesources Of Rice In Direct Sowing And Study On The Cold Tolerance In Cold Region

With 75 varieties (or lines) of japonica studying on cold tolerance at sprout stage, bud stage and simulate seedling emergence under low temperature direct sowing and the difference caused by cold among the varities at mature stage.Combinning the cold tolerance of varities at different growth period to reflect the need of germplasm resources that fitting for the direct sowing under cold region. The results were as follow:It exist most significantly difference between varieties in germinability, germination rate .germination coefficient, sprouting days and sprouting index at 10℃ and 25℃.The order of coefficient of variation from big to small were as follow.germination coefficient under 10℃ >average sprouting days under 25℃> average sprouting days under 10℃>germination coefficient under 25℃>germinability under 10℃>germination percentage under 10℃>germinability under 25 ℃>germination percentage under 10℃. Based on the sprouting index that reflected sprouting speed and sprouting numbers under 10℃ and 25℃, the tested varieties can be divided to sensitive type, middle type and cold tolerance type. It is very significantly positive correlation between the germinability .germination percentage and germination coefficient under 10℃, but they were very significantly negative correlation with average sprouting days. Germination coefficient under 25℃ was significantly positively correlated with germinability under 10℃ and germinability under 25 ℃, but negative correlated with average sprouting days under 10℃. Sprouting index under 10 ℃ was very significantly correlated with germinability under 10℃, germination percentage under 10 ℃, germination coefficient under 10 ℃, germination coefficient under 25 ℃ and sprouting index under 25 ℃, but very significantly negative correlation with average sprouting days.The descending value of sprouting index was very significantly positive correlation with average sprouting days and was very significantly negative correlation with germinability, germination coefficient and sprouting index under 10℃.According to choosed characteristic root, characteristic vecter and standard genotype value of each traits resources of japonica at sprouting stage, bud stage and the condition of simulating direct sowing under low temperature, we calculated 3 major components of 75 varieties. The choosed 3 major components can well evaluate cold tolerance instead of criteria of cold tolerance for different germplasm resource at sprouting stage ,bud stage and seedling stage of direct sowing .The varietieswhich have a big value for first major component have a strong sprouting capacity ,so it is suitable for the demand of direct sowing under low temperature .The varieties which have a big value for second major component showing lots of died seedless and fewer seedling emergence under low temperature in the experiment of varieties' cold tolerance, result in a decendence of germinability termination percentage .germination coefficient and sprouting index. The varieties who have a big value for third major component have lots of average sprouting days under 25 °C general temperature and fewer seedling emergence under low temperature direct sowing , result to a descendent of germinability , germination percentage and germination coefficient. According to the same demand of three major components, we choosed 14 varieties which have better cold tolerance, lots of varieties have cold tolerance in single stage and fewer varies have a better cold tolerance in every stage.There are great damage among the varities between cool-summer damage due to delayed growth and cool-summer damage due to impotency at rice growth period.75 tested varities were irrigated with cold water, in which 85% among the varities have more than 50% germination percentage. According to the grades of reproductive index, evaluation showed that all tested varieties have a stronger cold tolerance at booting stage. But the investigation result at booting emergence showed that date of booting emergence had a clearly delay after treatment and the difference is notable in different varieties. Tested material have strong cold tolerance to cold damage at booting stage,but the varieties which have weak cold tolerance is more sensitive.all the tested varities were deeply irrigated for a long time with cold water at growth period,which is mostly sensitive for low temperature at late booting stage ,but is not sensitive at booting stage.the booting emergence of irrigating deeply for a long time.the booting emergence of irrigating deeply for a long time which cold water is not noticablly delayed when it was compare to the period of booting stage.