The sweetpotato whitefly, Bemisia tabaci, has been a destructive pest in China for over the past two decades. It is an extremely polyphagous insect, being recorded feeding on hundreds of host plants around the world. ...The sweetpotato whitefly, Bemisia tabaci, has been a destructive pest in China for over the past two decades. It is an extremely polyphagous insect, being recorded feeding on hundreds of host plants around the world. Potential host plants and natural enemies of B. tabaci in the south, southeast, middle, north and northwest of China were investigated during the last decade. In total 361 plant species from 89 families were recorded in our surveys. Plants in the families Compositae, Cruciferae, Cucurbitaceae, Solanaceae and Leguminosae were the preferred host species for B. tabaci, which therefore suffered much damage from this devastating pest due to their high populations. In total, 56 species of parasitoids, 54 species of arthropod predators and seven species of entomopathogenic fungi were recorded in our surveys. Aphelinid parasitoids from Encarsia and Eretrnocerus genera, lady beetles and lacewings in Coleoptera and Neuroptera were found to be the dominant arthropod predators of B. tabaci in China. The varieties of host plant, their distribution and the dominant species of natural enemies of B. tabaci in different regions of China are discussed.展开更多
The effect of transgenic double genes, Cry1A + CpTI cotton and Cry1Ac toxinon the parasitoid, Campoketis chlorideae Uchida of cotton bollworm, Helicoverpa armigera (Huebner),was investigated in the laboratory. Helicov...The effect of transgenic double genes, Cry1A + CpTI cotton and Cry1Ac toxinon the parasitoid, Campoketis chlorideae Uchida of cotton bollworm, Helicoverpa armigera (Huebner),was investigated in the laboratory. Helicoverpa armigera larvae when in the first, second and thirdinstar could not survive if fed on transgenic cotton leaves. Consequently, C. chlorideae larvaecould not complete their development if parasitizing on such hosts. After H. armigera larvae werereared on transgenic or traditional cotton leaves for 12-48 hours, they were parasitized by C.chlorideae females. Parasitized larvae continued to feed on transgenic or traditional cotton for12-48 h. The present results showed that the body weight of larvae of the parasitoids weresignificantly reduced when parasitized hosts fed on transgenic cotton leaves compared to those fedon traditional cotton. Duration of egg and larvae stage were significantly prolonged, pupal andadult weight of C. chloridae was decreased when the host larvae fed on transgenic cotton leaveslonger than 48 h. The development duration of C. chlorideae pupae on the hosts fed on transgeniccotton leaves in each treatment was not significantly different from those of controls. Thelongevity of parasitoid females and males fed with a solution containing Cry1Ac toxin was notsignificantly different with that of the control.展开更多
Reproductive traits of one invasive population in Lake Fuxian and two native populations in Lakes Chao and Dongting for Pseudorasbora parva were investigated to determine the variations in their reproductive strategie...Reproductive traits of one invasive population in Lake Fuxian and two native populations in Lakes Chao and Dongting for Pseudorasbora parva were investigated to determine the variations in their reproductive strategies associated with the change of environmental conditions. Compared with the two native populations, P.parva markedly experienced the protraction in their spawning time and the decrease in mortality for adult individuals in Lake Fuxian. The three populations all got their first sexual maturity at the same age, but their total lengths at maturity were quite different for those in Lake Chao were significantly lower than in Lakes Fuxian and Dongting. Additionally, in spite that no significant difference occurred in their relative fecundities for P. parva in Lakes Fuxian and Dongting, the population in Lake Chao showed the markedly higher relative fecundity than the other two populations. These results were analyzed with the variations in water temperature, nutrient status, fishing stress among the three lakes. The relative decline in fecundity for the invasive population, which conflicted with the enemy release hypothesis, was disscussed with the context of the preponderance of another invasive fish, Neosalanx taihuensis, in Lake Fuxian.展开更多
The aphid quantity ratio（AQR） is defined as the number of aphids on each cultivar divided by the number of aphids on all cultivars. AQR is based on the correlation between aphid populations and their host plants and...The aphid quantity ratio（AQR） is defined as the number of aphids on each cultivar divided by the number of aphids on all cultivars. AQR is based on the correlation between aphid populations and their host plants and is an important tool that has been utilized in evaluating Medicago sativa（alfalfa） cultivar resistance to aphids. However, assessment of alfalfa resistance to aphids can be confused by the presence of aphid predators, causing the assessment of plant resistance to aphids to be based on incorrect aphid population data. To refine the AQR and account for the effect of predators on aphid population assessments, we introduced a parameter ‘α＇, corresponding to the predator quantity ratio, and used αAQR as the ratio to quantify aphid populations. Populations of both aphids（4 species） and their predators（12 species） occurring in 28 M. sativa cultivars were sampled over two years at a research station near Cangzhou, Hebei Province, China. Results showed that the most suitable evaluation period was from May to June, as the aphid population was stable during this period. Compared with the AQR method, the predator population numbers based on the αAQR had a significant inverse relationship with aphid population numbers and the 28 cultivars were clustered into three classes： the resistant class, tolerant class, and susceptible class. In addition, 17 cultivars were reassigned when evaluated using αAQR. All numerical values calculated by αAQR were displayed as a Gaussian distribution, which showed that the 28 cultivars could be clustered into nine groups using a median value（±SE） of 1±0.1. Hence, ongoing alfalfa breeding trials will be assessed using the αAQR to establish a robust system that includes agronomic performance parameters in order to generalize the new method for further studies.展开更多
Natural enemy insects are important factors in regulating plant invasion. The interactions between multiple insect species resulting from invasive plants remain poorly understood despite their potential. We observed n...Natural enemy insects are important factors in regulating plant invasion. The interactions between multiple insect species resulting from invasive plants remain poorly understood despite their potential. We observed notorious invasive plants Eupatorium adenophorum Sprengel were competedly fed by Solenopsis invicta Buren (Hymenoptera: Formicidae) and Dorylus orientalis Westwood (Hymenoptera: Formicidae) beside the scientific research base of Kunming University. It was first observed that D. orientalis was eating the epidermis, cortex, phloem and other root and stem tissues of E. adenophorum in soil. Two months later, it was observed that S. invicta ate the epidermis, cortex, phloem and other aboveground stem tissues of E. adenophorum. S. invicta attacked D. orientalis and displaced their living space by causing the later dead, injured, or even disabled. This phenomenon suggested that local herbivorous insects have adapted to E. adenophorum well, which will intensify the naturalization process of E. adenophorum in local habitats. In a homogeneous garden planting experiment of E. adenophorum conducted at the experimental base of Kunming University, the biomass of the introduced (China) populations of E. adenophorum was lower than that of the native (Mexico) populations, although there was no statistically significant difference. These results indicate a possible positive correlation between the increase in natural enemy pressure and the decrease in fitness of E. adenophorum.展开更多
In the field of biological control of agricultural and forestry pests,natural enemy insects play an important role,constituting the core of modern integrated pest management(IPM)strategy,providing solid support for th...In the field of biological control of agricultural and forestry pests,natural enemy insects play an important role,constituting the core of modern integrated pest management(IPM)strategy,providing solid support for the zero growth goal of chemical pesticide use,and helping the sustainable development of green agriculture.The rise of the natural enemy insect industry has become a key driver of the transformation of green agriculture,injecting vitality into the sustainability and ecological protection of agriculture.With the increasing concern about food safety,environmental protection and ecological balance all over the world,the application scope of natural enemy insects as biological control means is constantly expanding.Its unique ecological adaptability and environmentally friendly characteristics help to reduce dependence on chemical pesticides,ensure the safety of agricultural products and maintain ecological diversity.The purpose of this study is to analyze the current situation of natural enemy insect industry,evaluate its cost and benefit,emphasize its great significance in promoting the transformation of green agriculture,improving production efficiency and promoting ecological protection by drawing lessons from foreign successful experiences,and explore an efficient and sustainable new agricultural development model.展开更多
To safely and sustainably utilize genetic breeding techniques for crop production, greater understanding of the potential effects of genetically modified herbicide-tolerant（GMHT） crops on the ecological functions of...To safely and sustainably utilize genetic breeding techniques for crop production, greater understanding of the potential effects of genetically modified herbicide-tolerant（GMHT） crops on the ecological functions of predators is required. In the laboratory, we examined the functional and numerical responses of Cyrtorhinus lividipennis Reuter to eggs of brown planthopper（BPH）, Nilaparvata lugens（St？l）, which were reared on GMHT rice Bar68-1; the untransformed parental cultivar, D68; or a BPH-susceptive rice variety, Taichung Native 1. All stages of nymphs and female adult of C. lividipennis, either on GMHT rice or control plants, exhibited typical type II functional responses when fed on BPH eggs; the attacking rate and handling time of C. lividipennis on GMHT rice Bar68-1 was not significantly different from that on D68. The numerical responses of C. lividipennis on GMHT rice or controls fit Beddington＇s model; there were no significant differences in the parameters of numerical responses between GMHT rice Bar68-1 and D68. The results indicated that the functional and numerical responses of C. lividipennis to BPH eggs are not affected by GMHT rice Bar68-1.展开更多
One concern about the use of transgenic plants is their potential risk to natural enemies. In this study, using the eggs of the rice brown planthopper, Nilaparvata lugens, as a food source, we investigated the effects...One concern about the use of transgenic plants is their potential risk to natural enemies. In this study, using the eggs of the rice brown planthopper, Nilaparvata lugens, as a food source, we investigated the effects of Cry1 Ab rice on the biological characteristics and functional response of an important predator Cyrtorhinus lividipennis. The results showed that the survival ability（adult emergence rate and egg hatching rate）, development（egg duration, nymphal developmental duration）, adult fresh weight, adult longevity and fecundity of C. lividipennis on Bt rice plants were not significantly different compared to those on non-Bt rice plants. Furthermore, two important parameters of functional response（instantaneous search rate and handling time） were not significantly affected by Bt rice. In conclusion, the tested Cry1 Ab rice does not adversely impact the biological character and functional response of C. lividipennis.展开更多
The slow growth-high mortality hypothesis （SG-HG） predicts that slower growing herbivores suffer greater mortality due to a prolonged window of vulnerability. Given diverse plant-herbivore-natural enemy systems resu...The slow growth-high mortality hypothesis （SG-HG） predicts that slower growing herbivores suffer greater mortality due to a prolonged window of vulnerability. Given diverse plant-herbivore-natural enemy systems resulting from different feeding ecologies of herbivores and natural enemies, this hypothesis might not always be applicable to all systems. This is evidenced by mixed support from empirical data. In this study, a meta- analysis of the SG-HM hypothesis for insects was conducted, aiming to find conditions that favor or reject SG-HM. The analysis revealed significant within- and between-group heterogeneity for almost a11 explanatory variables and overall did not support SG-HM. In this analysis, SG-HM was supported when any of the following 5 conditions was met： （1） host food consisted of artificial diet; （2） herbivore growth was measured as larval mass; （3） herbivores were generalists; （4） no or multiple species of natural enemies were involved in the study; and （5） parasitoids （i.e., parasitic insects） involved in the study were gregarious. SG-HM was rejected when any of the following 5 conditions was met： （1） herbivores were from the order Hymentoptera; （2） parasitoids from more than 1 order caused herbivore mortality; （2） parasitoids were specialists; （3） parasitoids were solitary; （4） parasitoids were idiobionts or koinobionts; and （5） single species of natural enemy caused mortality of specialist herbivores. All known studies investigated herbivore mortality for a short period of their life cycle. Researchers are encouraged to monitor herbivore mortality during the entire window of susceptibility or life cycle using life tables. Studies involving multiple mortality factors （i.e., both biotic and abiotic） or multiple natural enemy species are also encouraged since herbivores in nature face a multitude of risks during the entire life cycle. More comprehensive studies may increase our understanding of factors influencing the relationships between 展开更多
The thrips quantity ratio（TQR） model is an important tool for evaluating crop resistance to thrips based on the correlation between thrips quantities and cultivars. Unfortunately, it is inaccurate, and the results a...The thrips quantity ratio（TQR） model is an important tool for evaluating crop resistance to thrips based on the correlation between thrips quantities and cultivars. Unfortunately, it is inaccurate, and the results appear significantly inconsistent when analysing the same cultivars in the same field study. To improve this model, we first studied the resistance of 28 alfalfa cultivars to thrips in Cangzhou, Hebei Province, north China. The results showed that the most suitable evaluation period was from May to June, as the thrips population was stable during this period. Second, we found that the natural enemy population was significantly positively correlated with the thrips population density（R=0.7275, P〈0.0001）, which might influence resistance estimation. Hence, we introduced a parameter ‘α＇, corresponding to the natural enemy quantity ratio, to eliminate the effect of the natural enemy using ＂αTQR＂. Using the improved method, 28 cultivars were clustered into three classes： the resistant class, sensitive class, and median class. All numerical values were calculated for αTQR displayed as a Gaussian distribution. This information showed that all data should be divided into nine groups using a median value of 1±0.1 with an equal difference of 0.1. Based on the new standard cultivars, Gongnong 1, Alfaking, Cangzhou and Algonquin were classified as highly resistant cultivars; Zhongmu 3, Gongnong 2, Zhongmu 1 and Zhongmu 2 were classified in the resistant group; Queen was classified in the moderately resistant group; Derby, WL354HQ, KRIMA, Apex, 53 HR, SARDI 5 and Farmers Treasure were classified in the median class; WL319HQ, WL343HQ and Sitel were classified as the low sensitive group; WL440 HQ and SARDI7 as the moderately sensitive group; WL168HQ and Sanditi as the sensitive group; and SARDI 10, WL363HQ, FD4, WL323 and SOCA as the highly sensitive group.展开更多
基金The authors thank the anonymous reviewers for their constructive comments on the previous version of this manuscript. Thanks also to Tong-Xing Sun （Qingdao Agricultural University, China）, Jian Huang（Fujian Agriculture and Forestry University, China） and Zong-Qi Liang （Guizhou University, China） for iden- tifying the species of host plants, parasitoids and entomopathogenic fungi, respectively. This research was funded by the National Basic Research Program of China （973 Project, 2009CB119203）, the China National Natural Science Foundation （30871678, 31071732） and National Department Public Benefit Research Foundation （nyhyzx200803005）.
文摘The sweetpotato whitefly, Bemisia tabaci, has been a destructive pest in China for over the past two decades. It is an extremely polyphagous insect, being recorded feeding on hundreds of host plants around the world. Potential host plants and natural enemies of B. tabaci in the south, southeast, middle, north and northwest of China were investigated during the last decade. In total 361 plant species from 89 families were recorded in our surveys. Plants in the families Compositae, Cruciferae, Cucurbitaceae, Solanaceae and Leguminosae were the preferred host species for B. tabaci, which therefore suffered much damage from this devastating pest due to their high populations. In total, 56 species of parasitoids, 54 species of arthropod predators and seven species of entomopathogenic fungi were recorded in our surveys. Aphelinid parasitoids from Encarsia and Eretrnocerus genera, lady beetles and lacewings in Coleoptera and Neuroptera were found to be the dominant arthropod predators of B. tabaci in China. The varieties of host plant, their distribution and the dominant species of natural enemies of B. tabaci in different regions of China are discussed.
文摘The effect of transgenic double genes, Cry1A + CpTI cotton and Cry1Ac toxinon the parasitoid, Campoketis chlorideae Uchida of cotton bollworm, Helicoverpa armigera (Huebner),was investigated in the laboratory. Helicoverpa armigera larvae when in the first, second and thirdinstar could not survive if fed on transgenic cotton leaves. Consequently, C. chlorideae larvaecould not complete their development if parasitizing on such hosts. After H. armigera larvae werereared on transgenic or traditional cotton leaves for 12-48 hours, they were parasitized by C.chlorideae females. Parasitized larvae continued to feed on transgenic or traditional cotton for12-48 h. The present results showed that the body weight of larvae of the parasitoids weresignificantly reduced when parasitized hosts fed on transgenic cotton leaves compared to those fedon traditional cotton. Duration of egg and larvae stage were significantly prolonged, pupal andadult weight of C. chloridae was decreased when the host larvae fed on transgenic cotton leaveslonger than 48 h. The development duration of C. chlorideae pupae on the hosts fed on transgeniccotton leaves in each treatment was not significantly different from those of controls. Thelongevity of parasitoid females and males fed with a solution containing Cry1Ac toxin was notsignificantly different with that of the control.
基金funded by the Key Project for Knowledge Innovation of CAS(No.KSCX1-SW-13-04)the National Key Project for Basic Research of China (No.2009CB119200)
文摘Reproductive traits of one invasive population in Lake Fuxian and two native populations in Lakes Chao and Dongting for Pseudorasbora parva were investigated to determine the variations in their reproductive strategies associated with the change of environmental conditions. Compared with the two native populations, P.parva markedly experienced the protraction in their spawning time and the decrease in mortality for adult individuals in Lake Fuxian. The three populations all got their first sexual maturity at the same age, but their total lengths at maturity were quite different for those in Lake Chao were significantly lower than in Lakes Fuxian and Dongting. Additionally, in spite that no significant difference occurred in their relative fecundities for P. parva in Lakes Fuxian and Dongting, the population in Lake Chao showed the markedly higher relative fecundity than the other two populations. These results were analyzed with the variations in water temperature, nutrient status, fishing stress among the three lakes. The relative decline in fecundity for the invasive population, which conflicted with the enemy release hypothesis, was disscussed with the context of the preponderance of another invasive fish, Neosalanx taihuensis, in Lake Fuxian.
基金funded by the earmarked fund for China Agriculture Research System (CARS-34-07)the National Department of Public Benefit Research Foundation, China (201303057)
文摘The aphid quantity ratio（AQR） is defined as the number of aphids on each cultivar divided by the number of aphids on all cultivars. AQR is based on the correlation between aphid populations and their host plants and is an important tool that has been utilized in evaluating Medicago sativa（alfalfa） cultivar resistance to aphids. However, assessment of alfalfa resistance to aphids can be confused by the presence of aphid predators, causing the assessment of plant resistance to aphids to be based on incorrect aphid population data. To refine the AQR and account for the effect of predators on aphid population assessments, we introduced a parameter ‘α＇, corresponding to the predator quantity ratio, and used αAQR as the ratio to quantify aphid populations. Populations of both aphids（4 species） and their predators（12 species） occurring in 28 M. sativa cultivars were sampled over two years at a research station near Cangzhou, Hebei Province, China. Results showed that the most suitable evaluation period was from May to June, as the aphid population was stable during this period. Compared with the AQR method, the predator population numbers based on the αAQR had a significant inverse relationship with aphid population numbers and the 28 cultivars were clustered into three classes： the resistant class, tolerant class, and susceptible class. In addition, 17 cultivars were reassigned when evaluated using αAQR. All numerical values calculated by αAQR were displayed as a Gaussian distribution, which showed that the 28 cultivars could be clustered into nine groups using a median value（±SE） of 1±0.1. Hence, ongoing alfalfa breeding trials will be assessed using the αAQR to establish a robust system that includes agronomic performance parameters in order to generalize the new method for further studies.
文摘Natural enemy insects are important factors in regulating plant invasion. The interactions between multiple insect species resulting from invasive plants remain poorly understood despite their potential. We observed notorious invasive plants Eupatorium adenophorum Sprengel were competedly fed by Solenopsis invicta Buren (Hymenoptera: Formicidae) and Dorylus orientalis Westwood (Hymenoptera: Formicidae) beside the scientific research base of Kunming University. It was first observed that D. orientalis was eating the epidermis, cortex, phloem and other root and stem tissues of E. adenophorum in soil. Two months later, it was observed that S. invicta ate the epidermis, cortex, phloem and other aboveground stem tissues of E. adenophorum. S. invicta attacked D. orientalis and displaced their living space by causing the later dead, injured, or even disabled. This phenomenon suggested that local herbivorous insects have adapted to E. adenophorum well, which will intensify the naturalization process of E. adenophorum in local habitats. In a homogeneous garden planting experiment of E. adenophorum conducted at the experimental base of Kunming University, the biomass of the introduced (China) populations of E. adenophorum was lower than that of the native (Mexico) populations, although there was no statistically significant difference. These results indicate a possible positive correlation between the increase in natural enemy pressure and the decrease in fitness of E. adenophorum.
文摘In the field of biological control of agricultural and forestry pests,natural enemy insects play an important role,constituting the core of modern integrated pest management(IPM)strategy,providing solid support for the zero growth goal of chemical pesticide use,and helping the sustainable development of green agriculture.The rise of the natural enemy insect industry has become a key driver of the transformation of green agriculture,injecting vitality into the sustainability and ecological protection of agriculture.With the increasing concern about food safety,environmental protection and ecological balance all over the world,the application scope of natural enemy insects as biological control means is constantly expanding.Its unique ecological adaptability and environmentally friendly characteristics help to reduce dependence on chemical pesticides,ensure the safety of agricultural products and maintain ecological diversity.The purpose of this study is to analyze the current situation of natural enemy insect industry,evaluate its cost and benefit,emphasize its great significance in promoting the transformation of green agriculture,improving production efficiency and promoting ecological protection by drawing lessons from foreign successful experiences,and explore an efficient and sustainable new agricultural development model.
基金supported by the National Natural Science Foundation of China (31160365 and 31360437)the Special Fund for Agro-Scientific Research in the Public Interest in China (201403031 and 201303017)+2 种基金the Research Funds from Guangxi Academy of Agricultural Sciences, China (2014YP08 and 2014JZ07)the Program for Specially Hired Expert in Guangxi,Chinathe International Science & Technology Cooperation Program of China (2012DFA31220)
文摘To safely and sustainably utilize genetic breeding techniques for crop production, greater understanding of the potential effects of genetically modified herbicide-tolerant（GMHT） crops on the ecological functions of predators is required. In the laboratory, we examined the functional and numerical responses of Cyrtorhinus lividipennis Reuter to eggs of brown planthopper（BPH）, Nilaparvata lugens（St？l）, which were reared on GMHT rice Bar68-1; the untransformed parental cultivar, D68; or a BPH-susceptive rice variety, Taichung Native 1. All stages of nymphs and female adult of C. lividipennis, either on GMHT rice or control plants, exhibited typical type II functional responses when fed on BPH eggs; the attacking rate and handling time of C. lividipennis on GMHT rice Bar68-1 was not significantly different from that on D68. The numerical responses of C. lividipennis on GMHT rice or controls fit Beddington＇s model; there were no significant differences in the parameters of numerical responses between GMHT rice Bar68-1 and D68. The results indicated that the functional and numerical responses of C. lividipennis to BPH eggs are not affected by GMHT rice Bar68-1.
基金Financial support was provided by the National Genetically Modified Organisms Breeding Major Projects, China (2011ZX08012-004)the Zhejiang Provincial Natural Science Foundation of China (LQ13C030003)
文摘One concern about the use of transgenic plants is their potential risk to natural enemies. In this study, using the eggs of the rice brown planthopper, Nilaparvata lugens, as a food source, we investigated the effects of Cry1 Ab rice on the biological characteristics and functional response of an important predator Cyrtorhinus lividipennis. The results showed that the survival ability（adult emergence rate and egg hatching rate）, development（egg duration, nymphal developmental duration）, adult fresh weight, adult longevity and fecundity of C. lividipennis on Bt rice plants were not significantly different compared to those on non-Bt rice plants. Furthermore, two important parameters of functional response（instantaneous search rate and handling time） were not significantly affected by Bt rice. In conclusion, the tested Cry1 Ab rice does not adversely impact the biological character and functional response of C. lividipennis.
文摘The slow growth-high mortality hypothesis （SG-HG） predicts that slower growing herbivores suffer greater mortality due to a prolonged window of vulnerability. Given diverse plant-herbivore-natural enemy systems resulting from different feeding ecologies of herbivores and natural enemies, this hypothesis might not always be applicable to all systems. This is evidenced by mixed support from empirical data. In this study, a meta- analysis of the SG-HM hypothesis for insects was conducted, aiming to find conditions that favor or reject SG-HM. The analysis revealed significant within- and between-group heterogeneity for almost a11 explanatory variables and overall did not support SG-HM. In this analysis, SG-HM was supported when any of the following 5 conditions was met： （1） host food consisted of artificial diet; （2） herbivore growth was measured as larval mass; （3） herbivores were generalists; （4） no or multiple species of natural enemies were involved in the study; and （5） parasitoids （i.e., parasitic insects） involved in the study were gregarious. SG-HM was rejected when any of the following 5 conditions was met： （1） herbivores were from the order Hymentoptera; （2） parasitoids from more than 1 order caused herbivore mortality; （2） parasitoids were specialists; （3） parasitoids were solitary; （4） parasitoids were idiobionts or koinobionts; and （5） single species of natural enemy caused mortality of specialist herbivores. All known studies investigated herbivore mortality for a short period of their life cycle. Researchers are encouraged to monitor herbivore mortality during the entire window of susceptibility or life cycle using life tables. Studies involving multiple mortality factors （i.e., both biotic and abiotic） or multiple natural enemy species are also encouraged since herbivores in nature face a multitude of risks during the entire life cycle. More comprehensive studies may increase our understanding of factors influencing the relationships between
基金financial support by the earmarked fund for China Agriculture Research System (CARS-35-07)
文摘The thrips quantity ratio（TQR） model is an important tool for evaluating crop resistance to thrips based on the correlation between thrips quantities and cultivars. Unfortunately, it is inaccurate, and the results appear significantly inconsistent when analysing the same cultivars in the same field study. To improve this model, we first studied the resistance of 28 alfalfa cultivars to thrips in Cangzhou, Hebei Province, north China. The results showed that the most suitable evaluation period was from May to June, as the thrips population was stable during this period. Second, we found that the natural enemy population was significantly positively correlated with the thrips population density（R=0.7275, P〈0.0001）, which might influence resistance estimation. Hence, we introduced a parameter ‘α＇, corresponding to the natural enemy quantity ratio, to eliminate the effect of the natural enemy using ＂αTQR＂. Using the improved method, 28 cultivars were clustered into three classes： the resistant class, sensitive class, and median class. All numerical values were calculated for αTQR displayed as a Gaussian distribution. This information showed that all data should be divided into nine groups using a median value of 1±0.1 with an equal difference of 0.1. Based on the new standard cultivars, Gongnong 1, Alfaking, Cangzhou and Algonquin were classified as highly resistant cultivars; Zhongmu 3, Gongnong 2, Zhongmu 1 and Zhongmu 2 were classified in the resistant group; Queen was classified in the moderately resistant group; Derby, WL354HQ, KRIMA, Apex, 53 HR, SARDI 5 and Farmers Treasure were classified in the median class; WL319HQ, WL343HQ and Sitel were classified as the low sensitive group; WL440 HQ and SARDI7 as the moderately sensitive group; WL168HQ and Sanditi as the sensitive group; and SARDI 10, WL363HQ, FD4, WL323 and SOCA as the highly sensitive group.
