| Rice stripe disease, caused by Rice stripe virus (RSV), is one of the most serious rice diseases in subtropical and temperate regions. In China, losses of 20–30% have been observed commonly in regions where Oryza sativa var. japonica is grown due to climatic changes, changes in cultivation practice, and loss of variety resistance. Cultivating varieties with RSV-resistant has been proved to be the most economical and effective for disease control. Therefore, it is important to evaluate the resistance among the present cultivars and breed lines.Resistance of 25 varieties and bred lines was evaluated by natural infection in the field along Yellow River in Henan province. The insect amount of Laodelphax striatellus on them was investigated respectively at the same time. The results showed that only seven 7 varieties exhibited high resistant to RSV. There were significantly different in insect amount of L. striatellus among the different varieties. According to the results obtained in filed test, ten varieties with significantly different in resistance were selected to examine the resistance for disease and insect by force the insect eating on the seedlings in greenhouse. Percentage of varieties with resistance to RSV was 40%. Three of four resistant varieties expressed insect resistance i.e. 60% pest resistance score, which was consistent with the field results. Zhengdao-18 and Yujing-6 with significant difference in resistance were selected to be mix planted according fixed ratio in the field. The results showed that the effect of varieties mix planting on disease control was low (14.57% on average) and yield increased 2.44% on average compared to those planting single variety when they were mix planted according to 1:1 ratio.Twelve samples of RSV were collected from the same field during 2007 and 2008, for analyzing their CP, SP gene and IR sequences. These 12 CP sequences, together with 9 CP sequences formerly isolated from 9 different districts of 6 provinces in northern China in our lab, 4 CP sequences from Yunnan province and 1 CP sequence of T isolate from Japan were analyzed. Similarity of these 45 CP nucleotide sequences ranged from 93.4-100.0%. According to the phylogenetic tree, 4 CP sequences from Yunnan province were clustered as one group, others as the second group. On the other hand, Comparison of the SP gene sequences of these 12 RSV isolates with 6 SP sequences available in GenBank suggested 93.3-100% nucleotide similarity. Isolates from Yunnan province were grouped together, but the other 22 isolates clustered together. Similarities of deduced amino acid sequences of CP and SP gene of 12 isolates were 97.8-100% and 98.8-100% respectively. IR3 sequence of 9 isolates ranged from 705bp to 721bp with insertion and deletion of segments in different regions. Two type IR4 (654bp and 634bp, respectively) were found.In order to obtain transgenic rice plants with RSV resistance, 20 bp to 328 bp of conservative sequences (Hsp) in SP was chosen as target gene. The sense and anti-sense strands were constructed to vector pTCK303 respectively or together, so three types of recombinant vector were obtained (vector with sense strand, vector with anti-sense strand and vector with sense and anti-sense strand). Then these vectors were genetically transformed via Agrobacterium tumefaciens into callus of mature embryo of of rice cv. Aichiasahi. |
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