[Geographical populations of brown planthopper in Nanning of South China and in Vietnam: a comparative study].

A comparison was made on the differences of the geographical populations of brown planthopper (BPH), Nilaparvata lugens (Stål), collected from Nanning of South China and from Ha Noi, Ha Tinh, Hue, TP. Ho Chi Minh, and Song Cuu Long of Vietnam. The BPH populations from Nanning, Ha Noi, Ha Tinh and Hue could damage the rice varieties with Bph1 and bph2 genes, whereas the BPH populations from TP. Ho Chi Minh and Song Cuu Long showed stronger virulence to the rice varieties with Bph1, bph2, Bph3 and bph4 genes than the other populations. The survival rates of the nymphs from Nanning, Ha Noi, Ha Tinh and Hue populations on the rice varieties TN1, Mudgo and ASD7 were all above 52%, but those on the rice varieties Rathu Heenati, Babawee and Ptb33 were below 44%. The nymphs of the BPH populations from TP. Ho Chi Minh and Song Cuu Long on the TN1, Mudgo, ASD7, Babawee and Ptb33 had a survival rate of above 50%, but those on Rathu Heenati had a survival rate of below 50%. The nymphal development durations of the BPH populations from Nanning, Ha Noi and Hue were significantly shorter on TN1, Mudgo and ASD7 than on Rathu Heenati, Babawee and Ptb33, but for the BPH population from Ha Tinh, the nymphal development duration on TN1, Mudgo and ASD7, and on Rathu Heenati and Ptb33 had no significant difference. The nymphal development durations of the BPH population from TP. Ho Chi Minh on TN1 and ASD7 were significantly shorter than those on Rathu Heenati, Babawee and Ptb33, but for the BPH population from Song Cuu Long, the nymphal development durations on TN1, Mudgo, ASD7, Rathu Heenati, Babawee and Ptb33 had no significant difference. After infested for 192 h, the nymph density of the BPH populations from Nanning and Ha Noi was significantly lower on Rathu Heenati, Babawee and Ptb33 than on TN1, Mudgo and ASD7, that of the BPH populations from Ha Tinh was significantly lower on Babawee than on TN1, Mudgo, the BPH populations from Hue and TP. Ho Chi Minh had a significantly lower nymph density on Babawee than on TN1, Mudgo, ASD7 and Rathu Heenati, and the BPH population from Song Cuu Long had a significantly lower nymph density on Babawee and Ptb33 than on TN1 and ASD7. The virulence of the BPH population from Nanning was similar with that of the BPH populations from central and northern Vietnam, which was a new proof that the BPH in South China was migrated from the central and northern parts of Vietnam.

[Resistance stability of rice varieties to different biotypes of brown planthopper].

In order to develop an effective analytical and monitoring method in breeding rice varieties with higher resistance stability to brown planthopper (BPH), Tai's method (1971) was employed to estimate the resistance stability of twelve rice varieties to different biotypes of BPH. It was shown that light intensity, seedling age, and nitrogen application rate had significant effects on the resistance performance and stability of rice varieties to different BPH biotypes. Among the varieties with resistance to BPH biotype II, the RHT, RP1976-18-6-4-2, and Ptb33 showed stable, IR56 showed unstable, while IR36 and ASD7 showed the most unstable resistance; whereas among the varieties susceptible to BPH biotype II, the TN1 showed stable, Guihuazhan, Foshanyouzhan and IR26 showed relatively stable, while Guojing No. 4 and Mudgo showed unstable susceptibility. For the rice varieties resistant to BPH biotype Bangladesh, the RHT, RP1976-18-64-2 and Ptb33 presented unstable, and IR56 presented very unstable resistance; whereas for the varieties susceptible to BPH biotype Bangladesh, the Guihuazhan, Foshanyouzhan and IR26 performed stable, TN1 and IR36 performed unstable, and Guojing No. 4, Mudgo and ASD7 performed the most unstable susceptibility.