Identification Of Different Rice Varieties Resistance To Nilaparvata Lugens (st(A)L) And Associated Resistance Factors

In this study, the rice varieties with different resistance to Nilaparvata lugens were chosen as experimental materials. The corresponding indexes were investigated in these rice varieties, which include population dynamic of Nilaparvata lugens, leaf sheath structure scanning with environmental scanning electron microscope (ESEM), feeding behavior with electrical penetration graph(EPG) technology, growth, development and indoor life table of N. lugens. Altogether, the identification of some resistance factors to N. lugens provide us foundation for further screening rice varieties.The main results are as follows:N. lugens population dynamics on different rice varieties in the fieldN. lugens amounts on 15 main rice varieties in Xinyang, Henan province, were investigated. The results show that, N. lugens numbers reach maximum in Qingliangyou 916, with 1485 insects per 100 plants. Following areⅡyou 688 and Tefeng 2053 with 1023 and 1005 insects per 100 plants respectively. N. lugens occur at Zhenzhunuo and Fengnuo 801 with only 15 and 51 insects per 100 plants respectively, followed by Fengliangyou 916 with 243 insects per 100 plants. Besides, the N. lugens number on rest of nine rice varieties are distribute from 244 to 698 insects per 100 plants. The variance analysis and multiple comparison results confirm further the above results.Observation to leaf sheath epidermis of nine rice varieties by ESEMLeaf sheath epidermis of nine rice varieties were observed by environmental scanning electron microscope (ESEM), the results show that, high-susceptible group have smaller and lower density silica cells, rather shorter glochids and tenuous hairs. On the contrary, high-resistance group have larger and higher density silica cells, rather longer glochids and tenuous hairs. These physical characteristics may form physical obstacle when N. lugens stylet penetrate at the time of feeding, which partial reason why some rice varieties are high-susceptible, other are high resistance.Electrical penetration graph (EPG) research on feeding behavior of N. lugensThe feeding behavior of N. lugens were investigated by EPG, the results show that, the probe time and frequency by N. lugens in high-susceptible group is commonly, and take more long feeding time in phloem, Converse results were found in high-resistance group, which indicated that there may be resistance factors on the surface and/or in the body of rice varieties in high-resistance group.Analysis on parameters of growth, development and life table of N. lugens on nine rice varietiesN. lugens growth development and life table parameters were analyzed on different rice varieties by one insect per single tube method. The results show that, N. lugens is suitable in high-susceptible group with shorter growth period, longer adult longevity, longer body length, larger oviposition amount, higher survival rate and hatchability, compared with the high-resistance group. The life table parameters analysis indicated that, N. lugens net reproductive rate on Qingliangyou916, Gangyou 5330 and Tefeng 2053, which are high-susceptible varieties, is rather larger, compared with high-resistance varieties, Zhenzhunuo, Fengliangyou 916 and Fengnuo 801, which indicated that the varieties significantly affected net reproductive rate of N. lugen. Mean generation time, innate capacity for increase and population doubling time data analysis indicated that there are significant difference between high-susceptible group, moderate-resistance group and high-resistance group. Zhenzhunuo, Fengliangyou916 and Fengnuo801 show strong resistance to N. lugens with lower innate capacity for increase, lower finite rate of increase and longer population doubling time, there are significant difference between high-susceptible group, moderate-resistance group and high-resistance group, but no significant difference between high-susceptible group and moderate-resistance group. The index of population trend of N. lugens on all varietaes are greater than 1, which indicated that population will be increased. Most results show adult longevity is quite longer and developmental duration of eggs is quite shorter in high-susceptible group, butⅡyou 688 and Tefeng 2053, with longer growth period, smaller body length, lower innate capacity for increase, which indicated that there may be resistance factors on the leaf sheath epidermis of these 2 rice varieties, although the sap is favorite for N. lugens to suck extremely. N. lugens growth period on Fengnuo 801, a high-resistance varietiy, is quite shorter, body length is quite larger, but with shorter adult longevity, longer developmental duration of eggs, most important, 4 macropterous females emerged about wing form on this varietiy. These results indicated that Fengnuo 801 show rather higher insect-resistance. In addition, ESEM observation and EPG paremeters analysis indicated that the chemical factors, such as feeding stimulant, stimulate N. lugens to suck in Fengnuo 801. At the same time lack of physical resistance factors, but will make N. lugens to break through obstacle which obstruct penetration of stylet on leaf sheath epidermis, consist with the probing time and times on Fengnuo 801.Morphology of fertilized and non-fertilized eggs of N. lugensThe research show that, the eggs are not exactly fertilized laid by N. lugens. N. lugens population quantity in the field in fact were effected by non-fertilized and natural dead eggs. The results also show that eyespots appearance or disappearance and egg color change are used as standard to distinguish fertilized eggs from non-fertilized eggs during egg development.Morphology of wing types differentiation of N. lugensThe previous research show that N. lugens will migrate when macropterous individuals emerge in large numbers. Distinguishing macropterous and brachypterous means a lot for forecasting. The observation experiment of developmental process in each instar of N. lugens nymphs were carried out, the results show that wing type can be distinguished at the 5th instar of N. lugens nymphs. At the 5th instar of N. lugens nymphs, if forewing bud extend to terminal of posterior wing bud, even overpass it, the nymphs will develop into macropterous individual. Accordingly, if forewing bud not extend to terminal of posterior wing bud, separate it from terminal of posterior wing bud, the nymphs will develop into brachypterous individuals. It can precede the warning period at least 3 days, if investigate at the 5th instar of N. lugens, and predict the probability of macropterous appearance.