Genetic Analysis And Mapping Of Brown Planthopper Resistance In Rice Variety SD

The brown planthopper(BPH)(Nilaparvata lugens Stal) is one of the most serious pests in the rice growth areas of Asia. BPH can not onlydirectly harm rice plants by sucking the plant saps, but also indirectly harm rice by transmiting virus diseases, such as rice grassy stunt and ragged stunt. It caused rice plants turning into yellow and even killing over, known as "hopper burn", when BPH seriously attacked rice.Chemical control has played an important role in the control of BPH for a long time. But a mass of utilizing chemical pesticides can not only pollute the environment, kill many beneficial insects and even destroy the ecological balance, but also lead to BPH increasing its pesticide resistance. Practice has proved that utilization of rice varieties with BPH resistance is a cost-effective way for controling BPH.Arice variety, namely SD, with highly BPH resistance had been screened from germplasm by Crop Research Instituteof Sichuan Academy of Agricultural Sciences. In this study the BPH resistance, and thegenetics of SD variety were identified and analyzed, and mapping of the BPH resistance gene of SD variety was also conducted.The main Results were as follows:1. The variety SD had stable risistance through the whole growth period. For evaluating the BPH resistance of SD, variety PTB33 as resistance contrast and variety TNI as susceptible contrast at seedling stage, tillering stage and adult-plant stage, three identification method were conducted using standard seedbox screening (SSBS), honeydew excretion and semi-field screening.The SSBS was used to evaluate the BPH resistance of seeding plants. The results showed that the average level of resistance were 1.50 for SD,0.76 for PTB33,8.67 for TN1, respectively. The amount of honeydew method was used to evaluate BPH resistance of tillering plants.The results showed that the average area of honeydew were 7.14 mm2 for SD,0.83 mm2 for PTB33,171.83 mm2 for TN1, respectively. In order to reevaluate BPH resistance of adult-plant, the individual identification method was used. The results showed that only 2-3 leaves of SD died when TN1 completely died.2. The results indicate that There is a dominant resistant gene in SD, and provisionally named "Bph-SD". To perform genetic analysis for BPH resistance in SD, an F2 population and F23 families both derived from a cross between the resistance Variety, SD, and the susceptiblevariety, TN1 were used; and an three way-cross population crossing between the susceptible line, G46A, and F1 (TN1×SD) was constructed. The BPH resistance of 273 SD×TN1 F2:3 families were evaluated by standard screening techniques. In the F23 families, the ratio of resistance families:separate families:susceptible families is 70:131:72. It fit the ratio of 1:2:1(χ2=0.361<χ0.05.22=5.99) by χ22test. It indicated that there is a dominant gene in SD. In the three way-cross population the ratio of resistance individuals:susceptible individuals is 122:153. It fit the ratio of 1:1(χ2=3.28<χ0.052=3.84) by χ2tests. It further evidence that there is a dominant resistant gene in variety SD.3. The SSR markers, InDel markers and SNP markers were used to map Bph-SD in a recessive population from TN1×SD F2:3progenies. The results showed that the resistance gene, Bph-SD was mapped on the short arm of chromosome4, located between the SNP maker SN8 and SN11, and their genetic distance were 2.8cM and 2.8cM, respectively. And the DNA makers RM16489、HST3、SN9 were identified to coseparation with Bph-SD. Above all the variety SD had stable risistance through the whole growth period, and it can pass the resistance to generations stably. The resistance of SD was controlled by a single dominant gene Bph-SD. And Bph-SD was mapped on the short arm of chromosome 4. located between the SNP maker SN8 and SN11.