Xiaoping Yu

Dynamics of Yeast-like Symbiote and Its Relationship with the Virulence of Brown Planthopper, Nilaparvata lugens Stal, to Resistant Rice Varieties

Abstract Abundance of the yeast-like symbiote (YLS) in brown planthopper (BPH), Nilaparvata lugens Stal, collected from rice fields in China and obtained from International Rice Research Institute (IRRI), was monitored. The role of YLS in nymph survival rate, development and adult reproduction, and activities of transaminases in BPH on different resistant rice varieties were examined. Also, the relationship between YLS and virulence shifts of BPH to resistant rice varieties was discussed. The results indicated that the virulence of BPH populations to resistant rice varieties was strongly related to the abundance of YLS in 5th instar nymphs and brachy-pterous females of BPH field populations at Nanning in South China and Hangzhou in East China, showing the more abundance of YLS in BPH, the higher virulence of BPH to resistant rice varieties, while no obvious differences in YLS abundance were monitored between three BPH biotypes. Numbers of YLS reduced significantly in female adult of BPH biotype 1 fed on resistant rice varieties IR26, Mudgo and ASD7, compared with that fed on susceptible rice variety TNI. The lowest YLS abundance of BPH from field population was found in 2nd generation successively fed on resistant varieties, and the number of YLS was resumed at 4th generation when the BPH has adapted the resistant varieties. The markedly lower nymphal survival rate, adult fecundity and activities of alanine and aspartic transminase, and significantly longer nymph duration in the three aposymbiotic biotypes than in the symbiotic ones were recorded on both susceptible and resistant rice varieties. However, the much greater differences between aposymbiotic and symbiotic BPH were found on the inadaptable resistant rice varieties than that on the fitness resistant rice varieties. Those results implied that YLS in BPH should play a crucial role in the virulent shift of BPH populations to resistant rice varieties.

The Biotypes, Wing-forms and the Immigration of Brown Planthopper, Nilaparvata lugens Stal, in Zhejiang Province, China

Abstract The virulence change (biotype), wing form development and immigration of brown planthopper (BPH) Nilaparvata lugens Stal, population in Zhejiang province was studied as compared to these BPH populations collected from Guangxi and Yunnan province, China and Philippines. The results indicate that the Zhejiang population could successfully infest variety IR26 and Mudgo after 1989, and ASD7 and IR36 after 1998, showing the characters of BPH biotype 2 and biotypes 3. The BPH tropical populations such as Guangxi population, however, adapted the resistant varieties IR26, Mudgo and ASD7 earlier. In 1997, the nymphal survival indices of Guangxi and Yunnan populations on Rathu Heenati (Bph3) were up to 70.9 and 66.7 respectively, higher than Zhejiang population. The Zhejiang populations show low brachupterous rates and have a negative correlation with nymphal density, belonging to the temperate type. The Philippine populations are almost brachypterous, however, the brachypterous rates of BPH males raise with the increase of nymphal density. The Guangxi population has a high brachypterous rate, being similar to the tropical type. On the other hand, tests showed that the lowest survival rate, longer duration of nymphs and the lightest weight of brachypterous female occurred in the 2nd generation of BPH after continuously feeding on resistant variety. Physiologically, the highest activities of superoxide dismutase (SOD) and catalase (CAT) were detected in the second generation of the BPH feeding on resistant rice variety.

THE VIRULENCE CHANGE AND DAMAGE CHARACTERISTICS OF VARIOUS GEOGRAPHIC POPULATIONS OF BROWN PLANTHOPPER

Abstract  The virulence change and damage characteristics of brown planthopper (BPH), Nilaparvata lugens Stal, populations collected from Guangxi, Yunnan and Zhejiang Provinces were studied by using various resistant rice varieties. The results indicated that the Zhejiang population could successfully infest varieties IR26 and Mudgo, showing the characters of BPH biotype 2 after 1989. The Guangxi population, however, could adapt the resistant varieties IR26, Mudgo and ASD7 after 1991. In 1997, the nymphal survival indices of Guangxi and Yunnan populations on Rathu Heenati (Bph3) were up to 70. 9 and 66. 7 respectively. This may imply that the BPH populations in Guangxi and Yunnan have shifted into a new biotype.

EFFECTS OF AGROCHEMICALS ON BROWN PL THOPPER NILAPARVATA LUGENS (STÅL) AND ITS PREDATORY ENEMIES

Abstract  The effects of agrochemicals on brown planthopper (BPH), Nilaparvata lugens, three predators were studied. The results showed that with recommendatory concentrations of 0. 30preti‐lachlor EC could cause high mortalities to adults of BPH, Microvelia horvathi and Cyrtorhinus lividipennis; 0. 50 butachlor EC had significant lethal effects on adults of M. horvathi and C. lividipennis, but had negligible effects on BPH and Erogonidium graminicolum; and 40% acetochlor WP had no obvious killing effect to other insects mentioned above, except C. lividipennis. Effects of 0. 50 quincolorac WP, 0. 10 bensulfuron methyl WP, 0. 10 cyclosulfumuron WP and 0. 20 daofuxing WP on these insects were insignificant. As far as fungicides were concerned, 2nd‐3rd instar nymphs of BPH and adults of Microvelia horvathi, and Cyrtorhinus lividipennis were obviously sensitive to 0. 40 IBP EC, but 0. 75 chlorothalonil WP 0. 20 tricyclazol WP, 0. 50 carbendazin WP, 0. 25 yekuling WP, 0. 5 jinggangmycin SL and 0. 20 yeqing shuang WP had no evident effects on them. 0. 4635 urea G had also no obvious insecticidal activity on adults of these insects. The results of toxic regression expression and LC50 of IBP, pretilachlor, butachlor and acetochlor to BPH and its predators were determined.