Dormancy And Cold Colerance Of Seed Germination For Weedy Rice Populations In China

Rice is one of the most important food crops in the world.In recent years,with the increase of labor costs,water restrictions and light and simple cultivation of rice,weedy rice broke out all over the world and cause serious damage to rice production.It gradually got people's attention.The existence of rice not onlyreduced rice production and also also affect the quality of rice.The existence of weedy rice not only causes the decrease of rice yield,but also affects the quality of rice,and further affects the commercial value of rice.But there are few studies on the characteristics of dormancy and cold tolerance in the whole country so far.The research on the degree of dormancy and cold tolerance at germination period will increase the understanding of the physiological characteristics of weedy rice,and then understand the adaptability characteristics of weedy rice,and provide a scientific basis for the prevention and control of weedy rice.This study mainly focuses on the following two aspects:1.Dormancy for weedy rice populations in China:With the gradual reduction of labor force,mechanization,and light cultivation technology for promotion,the scope of weedy rice has been expanded to the whole country.Weed Research Laboratory of Nanjing Agricultural University carried out investigation and collection of weedy rice and corresponding cultivated rice(cultivars)from the whole national rice area.Therefore,75 weedy rice populations and the corresponding cultivated rice were planted in the same homogeneous plantation.We harvested the seeds as test materials,determinated germination rate at optimum growth temperature(25 ?)under the normal state and breaking dormancy state,and then evaluated and analyzed.The results are as follows:(1)The germination test of 75 weedy rice populations and the corresponding cultivated rice samples in our country paddy field was showed thatthe lowest germination rate of of weedy rice and the corresponding cultivated rice at 7 days were 73.89%and 72.22%,the highest both reached 100%;the lowest germination rateof weedy rice and thecorresponding cultivated rice at 14 days were 88.89%and 83.33%,the highest also reached 100%.According to the dormancy classification:germination rate greater than 90%was considered none dormancy;germination rate between 71%-90%was considered mild dormancy;germination rate between 41%-70%was considered moderate dormancy,weedy rice in China were detected for none dormancy or mild dormancy.(2)The independent sample T test showed that the germination rate of T1,T2,T4,T3 was not significantly different between the germination rate of weedy rice and the corresponding cultivated rice.Corresponding collection analysis between weedy rice and the corresponding cultivated rice showed that weedy rice and the corresponding cultivated rice germination rate showed a extremely significant correlation,indicating that the weedy rice and the corresponding cultivated rice were closer at evolution relationship.It supported weedy rice in China may be derived from the local cultivated rice varieties in the seed germination rate characteristics.(3)Correlation analysis between germination rate of weedy rice/the corresponding cultivated rice and geographic information of sample showed thatgermination rate of weedy rice/the corresponding cultivated rice and latitude were significant or extremely significant negative correlation,and habitat temperature(annual average temperature and the average temperature after harvest two months)were significant or extremely significant positive correlation,namely with increasing latitude and decreasing temperature of the habitat,seed germination rate decreasing andthe dormancy increasing..2.Cold tolerance of seed germination for weedy rice populations in China:Chilling injury is an outstanding universal abiotic stresses in cultivated rice production,causeing a series of problems on rice seed germination and plant growth,affecting the quality of rice and yield reduction.So 75 weedy rice populations and the corresponding cultivated rice were planted in the same homogeneous plantation.We harvested the seeds as test materials,determinated germination rate at low temperature(15?)under the normal state and breaking dormancy state,and then evaluated and analyzed.(1)This study selected 15 ? as low temperature,determinated seed germination ratio respectively in 7 days and 14 days.The results showed that weedy rice was generally resistant to cold,andthe amount of weedy rice resistance to cold was significantly higher than that of the cultivated rice,.Among them,the samples which reached the first level of resistance for cold atwithout breaking dormancy and breaking dormancyoccupied 60%and 70.67%respectively,more than half belong to cold tolerance varieties,widely distributing in the rice for area of weedy rice.The cold tolerance of Yunnan Yuanjiang weedy rice populations(WRYN023)and their corresponding cultivated rice are strongest.Further,it is good for the development of rice cultivation to explore the genetic resources with strong cold tolerance for application and conducive to the development of rice cultivation.(2)The independent sample T test showed that the germination rate of T5,T6,T7,T8 was not significantly different between the germination ratio of weedy rice and the corresponding cultivated rice.The germination ratio of weedy rice was significantly higher than that of the corresponding cultivated rice,P values were 0.000,0.000,0.001,0.000,respectively.It is proved that the cold resistance of weedy rice is stronger than that of the cultivated rice varieties.Correlation analysis between germination rate of weedy rice/the corresponding cultivated rice and geographic information of sample showed thatgermination rate of weedy rice/the corresponding cultivated rice and latitude were significant or extremely significant negative correlation at the treatment T5 and T7,While other treats showed no correlation.This result may be due to the wide distribution of various rice areas in our country.Differences in geographic and topographic are significant,so there are only some correlation in each treatment.(3)Paired sample T-test analysis of weedy rice/the corresponding cultivated rice at 15 ?between withbreaking dormancy and without breakingdormancy treatment showed that:under the same temperature,treating same days,germination ratio of weedy rice/the corresponding cultivated rice withbreaking dormancy treatment is a extremely significant difference,namely germination ratio of withbreaking dormacy was significantly higher than that of without breaking dormancy.Moderate dormancy enhanced seed germination rate,in other words,dormancy can improvecold tolerance of seed germination.