Mirids secrete a TOPLESS targeting protein to enhance JA-mediated defense and gossypol accumulation for antagonizing cotton bollworms on cotton plants

Most coexisting insect species exhibit stunted growth compared to individual species on plants.This phenomenon reflects an interspecific antagonism drawing extensive attention,while the underlying mechanisms remain largely uncharacterized.Mirids(Apolygus lucorum)and cotton bollworms(Helicoverpa armigera)are two common cotton pests.We identified a secretory protein,ASP1,from the oral secretion of mirids,found in the nucleus of mirid-infested cotton leaves.ASP1 specifically targets the transcriptional co-repressor TOPLESS(TPL)and inhibits NINJA-mediated recruitment of TPL,promoting plant defense response and gossypol accumulation in cotton glands.ASP1-enhanced defense inhibits the growth of cotton bollworms on cotton plants,while having limited impact on mirids.The mesophyll-feeding characteristic allows mirids to avoid most cotton glands,invalidating cotton defense.Our investigation reveals the molecular mechanism by which mirids employ cotton defense to selectively inhibit the feeding of cotton bollworms.

Spatial Distribution Pattern and Application of Fourth-Generation Mature Larvae of Cotton Bollworm(Helicoverpa armigera Hübner) in Corn Field

[ Objective] The paper was to study the spatial distribution pattern of fourth-generation mature larvae of cotton bellworm in corn field. [ Method] The plots with different occurrence densities of fourth-generation cotton bollworm were investigated from August to September in 2009. Six groups of sampling data were obtained, and seven indicators including aggregation index method, Iwao method and Taylor method, etc. were used to determine its spatial distribution pattern. [ Result ] Aggregation index test showed that in all plots, Moore I 〈 0, Lloyed m＊/m 〈 1, Kuno Ca 〈 0, diffusion coefficient C 〈 1, diffusion index 16 〈 1, negative binomial distribution K 〈 0, indicating that mature larvae of cotton bollworm showed uniform distribution in summer corn. Iwae regression equation of fourth-genera- tion mature larvae of cotton boUworm in summer corn was m ＊ = 0. 090 6 ＋ 0. 766 9 m, r = 0. 986 3, indicating that the basic components of cotton bollworm distribu- ted was single individual, and mature larvae of cotton bollworm in summer corn showed uniform distribution. The optimal sampling number of fourth-generation ma- ture larvae of cotton bollworm in corn under different population densities could be calculated using formula N1 = （ 1. 090 6/m -0. 233 1 ）/D2. [ Conclusion] The result provided basis for accurate evaluation of population quantities and variation law of cotton boUworm, as well as prediction and control of the pest.

Studies on the Relationship between Occurrence Degree of Cotton Bollworm and Rainfall

[ Objective ] The aim of the study is to investigate the factors causing the outbreak of cotton bollworm and to provide effective measures for controlling cotton bollworm. [ Method] Based on the analysis of the data about insect and weather situation in Luyi County in 32 years, the meteorological, prediction model was established for monitoring the quarterly or monthly occurrence trend of cotton bollworm. [Result] The cotton boillworm occurred slightly in the years with rainfalls of 3 months over 500 nm and severely in the years with rainfalls of 3 months： less than 400 rim. The results of correlation analysis show that annual occurrence degrees of cotton bollworm and occurrence degrees of 4^th generation of cotton bollworm are extremely negatively correlated with rainfall during June - August; the occurrence degrees of 3^rd and 4^th generations of cotton bollworm are also extremely negatively correlated with rainfall in July. [ Conclusion] The occurrence of cotton bollworm in field is heavily influenced by rainfall in at its occurrence stage; moreover, the rainfall during June - August is the decisive factors influencing the occurrence of cotton bollworm.

Selection of Homozygous Cotton Lines Transformed with Two Insect-Resistant Genes

A plant expression vector containing a chimeric Bt29K gene coding for the activated Cry1Ac protein and the arrowhead proteinase inhibitior gene API B were introduced into the cotton cultivar Jihe321 mediated by Agrobactertium tumefaciens. Based on the results of kanamycin resistant testing, PCR detection for both foreign genes and insect bioassay using Heliethis armigera , nine transgenic homozygous cotton lines with insect resistance of more than 90% and better agronomic traits were bred through six generations from the original transgenic plants. Results from insect bioassay and sequence analysis of the PCR products of plants from some homozygous lines indicated that the chimeric Bt29K gene was stably inherited in these transgenic cotton lines. The main agronomic characters of these homozygous cotton lines, such as boll productivity and fibre strength, were better than that of the original cotton cv. Jihe321.

Performances of the cotton bollworm,Heliothis armigera (Hubner) at different temperatures and relative humidities

The cotton bollworm, Heliothis armigera (Hubner) is an important insect species at-tacking many crops. Their performances have been examined at temperatures from 15℃ to 35℃ and relative humidities (RH) between 22.5% and 100%, respectively, in order to assess possible effect of climate in future on its occurrence and infestation. Durations of all developmental stages of the insect shortened with increasing temperature. The temperature favoring population growth ranged from 25℃ to 30℃.Larval duration and adult longevity decreased as relative humidity increased, but development of other stages was independent of RH. At RH of over 64%, their survival rate, egg production and oviposition rate varied a little, and all the population parameters of the insect remained at a relative constant level.

Efficiency of cotton bollworm (Helicoverpa armigera Hübner) control of different Bt cotton varieties in North China

Background： The cotton bollworm （Helicoverpa armigera） is one of cotton＇s most destructive insect pests in terms of yield and quality. Since 1997, China has grown commercially available transgenic Bacillus thuringiensis （Bt） cotton. We aimed to investigate the variation in resistance of transgenic Bt cotton varieties to cotton bollworm in North China. Methods： Populations of cotton bollworm were monitored from 2008 to 2015 in environments where Bt cotton was planted adjacent to other non Bt crops. The study included 197 Bt cotton varieties planted in 42 counties/locations in three provinces （Hebei, Shandong and Henan） of North China, which were evaluated through field investigations, bioassays, and enzyme linked immunosorbent assays （ELISA）. Results： The average number of cotton bollworms never exceeded the action threshold （10 larvae per 100 cotton plants）, however, their number reached 19.55 per 100 cotton plants in 2011. The ratios of damaged plants to total Bt cotton stem tips, buds, and bolls was low except in 2010, when the ratios reached 1.82%, 2.09%, and 10.63%, respectively. The results of bioassay showed that the corrected mortality were higher at the second generation cotton bollworm stage than the third and fourth germination stages. Totally, Bt protein content declined sharply at the seedling stage from 2008 to 2015. Conclusions： This study indicated that almost all Bt cotton varieties were capable to effectively control the populations of cotton bollworm in North China.

THE FUNDAMENTAL STRATEGY FOR THE CONTROL OF COTTON BOLLWORM OUTBREAKS IN CHINA

on the basis of the analysis of the factors causing the cotton bollworm outbreaks and control failure, the authors recommend that the fundamental strategy for solving the problem of cotton bollworms in China should be to conduct area-wide unified controls rather than depend on insecticides. The unified control system is the guarantee for Integrated Pest Management (IPM) for small-scale crop owners at present. So the authors call on policymakers to put stress on organizing individual growers to carry out area wide unified controls.

BIONOMIC OF CAMPOLETIS CHLORIDEAE (HYM:ICHNEUMONIDAE)AS A PARASITOID OF THE COTTON BOLLWORM HELICOVERPA ARMIGERA (LEP:NOCTUIDAE) *

The bionomics of Campoletis chlorideae and the regularity of its seasonal fluctuations were studied in Changsha district,Hunan province. Field investigation indicated that there were ten generations of C. chlorideae a year, of which seven occurred in cotton fields. Three peaks of cotton bollworm parasitization by C. chlorideae were observed, early May to late June, mid August to early September, mid September to mid October respectively. One peak occurred in tomato and tobacco fields, the other two in cotton fields. The parasitization rate ranged from 25.1%- 63.1%. The total development time from egg to adult ranged from 13.0 days at 32℃ to 75.5 days at 11.6℃. Each wasp could parasitize the 5-23 second instar larvae of tobacco caterpillar. C. chlorideae could parasitize the cotton bollworm, beet armyworm and tobacco caterpillar, but preferred the cotton bollworm larvae. C. chlorideae could parasitized 1st-3rd instar larvae of the tobacco caterpillar, but seldom parasitzed 4th-6th instar larvae. Moreover, C. chlorideae preferred second instar larvae. Theoretical models for developmental speed, adult longevity and the influence of temperature were proposed. The overwintering of C. chlorideae Uchida was also discussed. Moreover, methods for utilization of C. chlorideae Uchida in crop protection were presented and the bionomics of Campoletis chlorideae in both the Yangtze River Valley and Yellow River Valley were compared.

Determining the major Bt refuge crops for cotton bollworm in North China

Evaluation of the effectiveness of refuge strategies involved in cotton boll- worm Bt resistance management would be aided by technologies that allow monitoring and quantification of key factors that affect the process under field conditions. We hy- pothesized that characterization of stable carbon and nitrogen isotopes in adult bollworm, Helicoverpa armigera （Htibner） （Lepidoptera： Noctuidae） moths may aid in determining the larval host that they developed upon. We found moths reared from larvae fed on peanut, soybean or cotton, respectively, could be differentiated using isotopic analyses that also corresponded to their respective larval host origins. These techniques were then used to classify feral second-generation bollworm moths caught in Bt cotton （Gossypium hirsu- rum） fields into different populations based on their isotopic signatures. In 2006-2007 feral moths captured in Bt cotton fields predominantly correlated with the peanut （Arachis hypogea） having served as their larval host, indicating this is the most important refuge crop for Bt-susceptible bollworm individuals （providing 58%-64% individuals） during independent moth peaks for the second generation in North China. The remaining feral moths correlated with soybean （Glycine max） （0-10%）; other C3 plant （20%-22%） and non-C3 plant （12%-14%） host types also provided some Bt-sensitive moths. Field obser- vations showed that peanut constitutes the primary refuge crop contributing to sustaining Bt-susceptible moths dispersing into cotton in North China. These results suggest that peanut may be a more effective refuge to sustain Bt-susceptible bollworm individuals and reduce the risk of development of a Bt-resistant biotype.

How does atmospheric elevated CO2 affect crop pests and their natural enemies？ Case histories from China

Global atmospheric CO2 concentrations have risen rapidly since the Industrial Revolution and are considered as a primary factor in climate change. The effects of elevated CO2 on herbivore insects were found to be primarily through the CO2-induced changes occurring in their host plants, which then possibly affect the intensity and frequency of pest outbreaks on crops. This paper reviews several ongoing research models using primary pests of crops （cotton bollworm, whitefly, aphids） and their natural enemies （ladybeetles, parasitoids） in China to examine insect responses to elevated CO2. It is generally indicated that elevated CO2 prolonged the development of cotton bollworm, Helicoverpa armigera, a chewing insect, by decreasing the foliar nitrogen of host plants. In contrast, the phloemsucking aphid and whitefly insects had species-specific responses to elevated CO2 because of complex interactions that occur in the phloem sieve elements of plants. Some aphid species, such as cotton aphid, Aphis gossypii and wheat aphid, Sitobion avenae, were considered to represent the only feeding guild to respond positively to elevated CO2 conditions. Although whitefly, Bemisia tabaci, a major vector of Tomato yellow leaf curl virus, had neutral response to elevated CO2, the plants became less vulnerable to the virus infection under elevated CO2. The predator and parasitoid response to elevated CO2 were frequently idiosyncratic. These documents from Chinese scientists suggested that elevated CO2 initially affects the crop plant and then cascades to a higher trophic level through the food chain to encompass herbivores （pests）, their natural enemies, pathogens and underground nematodes, which disrupt the natural balance observed previously in agricultural ecosystems.