Tolerance Of Rice Varieties To The Brown Planthopper, Nilaparvata Lugens (ST(?)L) And Its Physiological Mechanisms

The brown planthopper (BPH), Nilaparvata lugens (Stal) is an important pest insect infesting rice in China and other Asian countries. BPH characterized by the monsoon migration, r-strategy and resurgence, has formed serious threat to rice production. Application of rice resistant variety has been demonstrated one of the most economic and effective ways to control BPH population. Virulent change of BPH population to resistant varieties had seriously affected the life-span of resistant varieties extended in rice production. Extension and application of tolerant varieties will both reduce occurring of BPH new virulence and merge into BPH IPM systems. But tolerance differentiation of rice varieties to BPH attack and its physiological mechanism has not made any progresses, which will hinder the establishing of screening methods and breeding of resistant varieites. Hence, based on virulence characteristics of BPH population in Zhejiang province and resistance evaluation of rice newly-bred varieties (lines) to BPH, tolerance characteristics of rice varieties to BPH attack, change of growth and physiological parameters of BPH-infested plants, and probing behaviour of BPH on different tolerant varieties were carried out. Physiological mechanism of rice tolerant variety was elucidated. The objective of this paper will be provided a theory basis for the screening of BPH-tolerant varieties and realization of BPH sustainable management. The results were as followings:1 Virulence monitoring of BPH population in Zhejiang provinceThe virulence characteristics of BPH population in Zhejiang province during 1999-2002 had changed, as compared to monitoring data of the year 1998. BPH biotype II in the year of 1998 had shifted into BPH biotype II by dominance and less biotype III, this indicated that BPH populations could be virulent to rice varieties with Bphl gene and with bph2 gene. The results showed that different temperatures (22℃ 26℃ 30℃) had great effects on virulence of BPH population on different resistant varieties. At lower temperature (20℃ -26℃), rice varieties had a longer resistance lasting period, and damage symptom of rice plant was expressed lately, at a higher temperature (30℃), rice varieties had a shorter durable period, damage symptom was displayed early.2 Resistance evaluation of newly-bred rice varieties (lines) to BPHResistance of 611 newly-bred rice varieties (lines) to BPH was evaluated using the method of the Modified Seedbox Screening Technique (MSST). The results showed that 61 resistance rice varieties were selected, and the resistance rate of rice varieties in tested varieties "was 9.98%;in which, 32 and 25 resistant varieties were graded 0-3 and 5, respectively, accounting for 5.4% and 4.75%, respectively; Moderately resistance or resistance varieties selected at seedling stage was further evaluated in adult stage in terms of resistance lasting period. The result showed that varieties Pei-ai 64S/E32, Triveni, Utri Rajapan and Jiayu 948, had middle resistance at rice seedling and adult stage, were selected for further study on tolerance of rice varieties to BPH.3 Tolerance characteristics of rice varieties to BPH and its population developmentTolerance and antibiosis components of 10 rice varieties were analysed using the Functional Plant Loss Index (FPLI) at rice seedling and adult stages. The results indicated that when plants were infested by eight 1-2 instars and 3-4 instars BPH nymphs at seedling stage, respectively, the plants expressed some difference in tolerant levels; For most rice varieties, plants infected with high instar nymphs had a reduction in resistance. The results of tolerance characteristics of rice varieties to BPH attack at rice seedling and adult stages showed that varieties Pei-ai 64S/E32, Triveni, Utri Rajapan belonged to a stronger tolerant group; Varieties IR64, Rathu Heenati are of high antibiosis; Varieties TNI, Shanyou 63 and Xiushui 11 are of susceptible; Varieties ASD7 and Jiayu 948 belong to both groups of tolerance and antibiosis.