Genetic Diversity Of Weedy Rice In The Changjiang And Huaihe River Valley Of China

Rice(Oryza sativa L.) is one of the most important world’s cereal crops. Nowadays,however,more and more weeds are occurring in rice fields, particularly the conspecific weedy rice(O.sativa f.spontanea). Weedy rice is one of the most notorious weeds found in rice-planting areas all over the world.It commonly causes reduction of rice yield and affects grain quality.Weedy rice is also called red rice,as most weedy rice has red pcricarp.Because of the affinity of weedy and cultivated rice,weedy rice is more difficultly controlled than other weeds in rice fields.On the other hand,as a primary gene pool of cultivated rice, weedy rice may provide a large amount of gene resources for rice breeding.Because of the change of cultivation methods and weed managements accelerate the growth and spread of weedy rice. In recent years,therefore,weedy rice has increasingly affected rice production in many regions of the world,including the Changjiang and Huaihe River Valley of China. Controlling weedy rice is an urgent problem.However,fully understanding the genetic backgrounds and biological characters of weedy rice is the prerequisite for effective control. Red pericarp is one of the basic characteristics of weedy rice(Oryza sativa L. f spontaneous). In order to determine the heredity of red pericarp, the new discovered weedy rice line W16, which collected from Yangzhong, Jiangsu Province, and02428were used as parents to make the reciprocal crosses, and the colour of the seeds of relevant F1, F2, F3generation were phenotyped. The results indicated that the red pericarp of weedy rice is controlled by single dominant nuclear gene, belonging to the typical maternal influence. White pericarp in rice has been shown to be due to a14bp deletion in Rc gene on chromosome7which encodes a Basic Helix-Loop-Helix Protein. An InDel marker, RID14, was developed based on the14bp deletion, and RID14was cosegregated with the colour of pericarp in the F2population, allowing to identify the homozygous red pericarp genotype, homozygous white pericarp genotype and heterozygous red pericarp genotype individuals. The RID14PCR products were sequenced from5selected weedy rice lines, and all the sequences are same with the common wild rice.24weedy rice lines which collected in1950s and in recent years from the region of Yangtze and Huaihe River,3common wild rice(O. rufipogon) from Guangxi province and423germplasm lines were tested with marker RID14, which allows discrimination between red pericarp and white pericarp rice varieties. The primers produce a154bp fragment from a red pericarp allele and a140bp fragment from a white pericarp allele, allowing simple analysis on PAGE or agarose gels.Therefore the RID14is a perferct marker to identify the red weedy rice from commercial cutivated rice.The strip disease resistance genes and field resistance of96weedy rice in Jiangsu province were studied by dominant marker ST10.727specific fragment of ST10were amplified in the five among ninety-six samples while PCR products were none found in others, suggesting five samples perhaps carried stv-bi gene and nonexistence of such gene were in other ninety-one samples. However, all of the ninety-six materials exhibited characters of resistance to rice strip disease, we presumed that ninety-one weedy rice materials may carry resistance gene other than stv-bi. This study can be as a referrence for the develop of disease resistance genes of the weedy rice.The rice blast resistance genes and field resistance of96weedy rice in Jiangsu province were studied by marker Pita. Suggesting two samples perhaps carried Pita gene and nonexistence of such gene were in other ninety-four samples. However, all of the ninety-six materials exhibited characters of resistance to rice strip disease, we presumed that ninety-four weedy rice materials may carry resistance gene other than Pita. This study can be as a referrence for the develop of disease resistance genes of the weedy rice.