Altered Host Resistance to Listeria monocytogenes In Mice Exposed to 1-Chloroacetophenone (CN) Vapours

Short term repeated exposure of 1-chloroacetophenone (CN) vapours at a concentration of 0.153 mg per litre for 15 minutes daily on 10 consecuitve days in Swiss albino male mice resulted in increased mortality to Listeria monocytogenes. Significantly elevated bacterial growth was observed in the spleen and liver of the CN exposed animals. The increased bacterial count in these organs was evident within 4-6 days post challenge as compared to vehicle exposed infected and unexposed infected animals. Increased susceptibility to infection has been considered to be the function of immune alteration due to cumulative short term effects ofCN vapour inhalation. This may be attributed to immunotoxic effects of CN on Tcells mediated macrophage functions.

Hatching and development of maize cyst nematode Heterodera zeae infecting different plant hosts

The occurrence, distribution, and rapid molecular detection technology of Heterodera zeae Koshy et al. 1971, have been reported in China. We explored the biological characteristics of H. zeae sampled in Henan Province, China to understand its interaction with plants. Cysts and second-stage juveniles(J2s) were identified under an optical and scanning electron microscope, internal transcribed spacer(ITS) phylogenetic tree, and sequence characterized amplified region(SCAR)-PCR analyses. The optimum hatching temperatures of H. zeae were 30°C and 28°C, with cumulative hatching rates of 16.5 and 16.1%, respectively, at 30 days post-hatching(dph). The hatching rate of H. zeae eggs was improved by 20-and 50-time maize soil leachate and root juice, and 10-time root exudates. The hatching rate in 10-time root exudates was the highest(25.9%). The 10-time root exudates of maize and millet produced the highest hatching rate at 30 dph(25.9 and 22.9%, respectively), followed by wheat(19.9%), barley(18.3%), and rice(17.6%). Heterodera zeae developed faster in maize than in other crops. Fourth-stage juveniles(J4s) were detected in maize roots 8 days post-inoculation(dpi) at 28°C but not in other crops. Combined with hatching tests, the Huang–Huai–Hai summer maize region and the south and central-southwest mountainous maize areas are highly suitable for H. zeae in China. This is the first systematically study of the hatching and infection characteristics on different plant hosts of corn cyst nematode H. zeae in temperate regions. This study laid a theoretical foundation for the rapid spread and high environmental adaptability of corn cyst nematode.

Genetic sources and loci for wheat head blast resistance identified by genome-wide association analysis

The emergence and spread of wheat blast caused by fungal pathogen Magnaporthe oryzae pathotype Triticum is a threat to global wheat production.The resistance level and genetic loci for blast resistance in Chinese germplasm remain unknown.A panel of 266 bread wheat accessions from China,CIMMYTMexico and other countries was screened for head blast resistance under 12 field experiments in Bolivia and Bangladesh.Subsequently,a genome-wide association study was performed to understand the genetic basis of wheat blast resistance.The average blast index of all the accessions was 53.7%±12.7%,and 10 accessions including Chinese accessions Yumai 10 and Yu 02321 showed moderate to high levels of blast resistance,accounting for only 3.8%in the panel.Fifty-eight significant SNPs clustered in a 28.9 Mb interval on the 2 AS/2 NS translocation region,explaining phenotypic variation between10.0%and 35.0%.The frequency of the 2 AS/2 NS translocation in the Chinese accessions was as low as4.5%.These results indicated that the 2 NS fragment was the only major locus conferring resistance to wheat blast in this panel,and the resistant and moderately resistant lines identified could be deployed in breeding.

Characterization and screening of cotton(Gossypium hirsutum L.)germplasm for leafhopper(Amrasca biguttula biguttula(Ishida))resistance

Background Cotton(Gossypium hirsutum L.)is one of the most significant fibre and cash crops and plays an important role in Indian industrial and agricultural economies.However,over the years quantity and quality have been hampered by the pest leafhopper.Leafhopper alone has been shown to cause yield losses of up to 40%.In this study,screening and evaluation were performed to identify and categorize 100 cotton genotypes along with 5 checks as resistant,moderately resistant,sensitive and highly sensitive to leafhoppers.Results A total of hundred genotypes were evaluated along with five checks for leafhopper resistance.Based on the screening results,a total of 19 genotypes were resistant to leafhoppers,which was on par with the findings of the check KC 3.The contents of total soluble sugar,total soluble protein,and total free amino acids were significantly positively correlated with the mean grade,whereas total phenols content and trichome density were significantly negatively correlated with the susceptibility grade.However,based on screening and biochemical analysis,the genotypes KC 2,JR-23,Samaru-26-T,D 4,TCH 1728,RS 253,and B-61-1862 exhibited high resistance to leafhopper.Conclusion According to the findings of this study,choosing genotypes with high total phenolics content together with high trichome density and low contents of total soluble sugar,total soluble protein,and free amino acids may aid in the development of resistant genotypes.

Field Evaluation of the Asian Corn Borer Control in Hybrid of Transgenic Maize Event MON 810

In this study, a transgenic Bt maize hybrid (event MON 810 from Monsanto Company) expressing Cry1Ab protein derived from Bacillus thuringiensis (Bt) and its negative isoline hybrid were evaluated for control of the Asian corn borer, Ostrinia furnacalis (Guenée) (Lepidoptera: Pyralidae), in a field trial. Maize plants were artificially infested with neonate larvae of Asian corn borer at the mid-whorl (first-generation), pre-tassel (first- and/or second-generation), and silk (second-generation) growth stages. The transgenic Bt maize hybrid sustained significantly less leaf feeding damage (rating 1.0±0.0) than its negative isoline control (rating 7.3±0.1). With the Bt maize, 1.36.8% of plants were damaged by corn borer tunneling with <0.5 cm tunneling per stalk under different levels of infestation, compared with 100% of plants damaged with 9.325.0 cm tunneling per stalk for the negative isoline control. On average, transgenic Bt maize hybrids had only 0.010.05 tunnels per stalk and no stems were broken. In contrast, the negative isoline control had 3.118.36 tunnels per stalk and 31.273.9% of stems broken. Yields were significantly higher in transgenic Bt maize than in the control. These results demonstrate that transgenic Bt maize can significantly minimize yield losses caused by the Asian corn borer through resistance to the first- and second-generation larvae.

Evaluating Protective Terpenoid Aldehyde Compounds in Cotton (Gossypium hirsutum L.) Roots

Cotton (Gossypium hirsutum L.) has epidermal glands containing terpenoid aldehyde (TA) compounds that protect the plant from pests and diseases. One TA, gossypol, has two forms (+) and (-) that are present in varying amounts. This study evaluated the variation in roots for TA compounds and how environment affected the levels of these compounds. Similar to seed, gossypol was the predominant TA in roots. No heliocides were detected with only trace amounts of other TAs, such as hemigossypolone or hemigossypol, detected in a few lines. Among the glanded lines, there were significant differences in gossypol content. Percent plus gossypol was consistently 4% - 10% higher in roots than seed. One line, “Mac7”, had 12 - 14 ug/mg gossypol in roots and 18 ug/mg in seed as well as >90% (+) gossypol in both roots and seed. Unlike other tissues in glandless cotton, the roots of glandless lines consistently produced detectable amounts of gossypol with 77% to 82% in the (+) form. Multi-year field tests showed that although gossypol levels in the roots were more affected by insect pressure or other environmental conditions than seed, there was selectable variation in upland cotton for root gossypol content. Unlike other parts of a glandless plant, the roots retained a functioning biochemical pathway for gossypol production.

Alectra vogelii: A Threat to Bambara Groundnut Production under Climate Change: A Review Paper

Bambara groundnut (BGN) is a protein-rich pulse with the ability to lead to more climate-resilient agriculture. The objective of this study was to review Alectra vogelii as a potential threat to BGN production as a result of climate change. However, the crop faces biotic and abiotic stresses. Alectra vogelii is a major biotic constraint to BGN production, especially in Africa’s non-fertile semi-arid regions. Alectra vogelii (L.) Benth is a parasitic weed in the Orobanchaceae family that causes major damage by forming haustoria attached to roots to enable absorption of nutrients from the BGN. Alectra vogelii produces a large number of minute seeds that can live in the soil for up to 20 years. Based on the reviewed literature, various control mechanisms for dealing with the harmful effects of Alectra vogelii have been proposed. The aim of this research was to reveal the effect of Alectra vogelii on BGN and possible control strategies. We discuss the different control methods such as cultural and mechanical management procedures, phosphorus fertilizers and resistant host crops, herbicide use, and integrated Alectra vogelii control methods. In adaptive methods, however, new techniques remain important. The life cycle of root parasitic weeds is inextricably linked to that of their host, making it an ideal target for such new control techniques, especially when aimed at the early stages of the host-parasite relationship. This review reveals additional information on the function of parasitic seed, strigolactones and how they can be used in breeding to management parasitic weeds.

High basal defense gene expression determines sorghum resistance to the whorl-feeding insect southwestern corn borer

Southwestern corn borer （SWCB, Diatraea grandiosella） and fall armyworm （FAW, Spodopterafrugiperda） are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing plant damage and yield losses from both insects. In this study, we evaluated 12 sorghum lines for whorl-stage resistance to leaf-feeding SWCB and FAW in greenhouse and laboratory bioassays. Differential plant responses were detected against the two insects. Among 12 lines tested, CM1821, Della and PI196583 were resistant to both insects, while BTx2752 was largely susceptible. Line R.09110 was resistant to SWCB, but susceptible to FAW, whereas Redbine-60 was suscep- tible to SWCB, but not to FAW. In addition, we quantified various chemical components in the plants and determined their association with insect resistance. Tannin and chloro- phyll in leaves did not show any significant correlation with resistance to either insects, but contents of soluble protein in general were negatively correlated with resistance to both insects. Endogenous soluble sugar and dhurrin were only positively correlated with resistance to SWCB, but not with FAW resistance. To gain some molecular insight into resistance mechanism of sorghum to SWCB, we performed qPCR reactions for key genes encoding enzymes involved in dhurrin and jasmonic acid （JA） biosynthesis on selected resistant or susceptible lines. Although these genes were rapidly and strongly induced by insect feeding in all lines, the observed resistance is likely explained by higher constitutive dhurrin contents in some resistant lines and higher basal JA biosynthesis in others. Our results suggest that sorghum utilizes multiple strategies to defend itself against SWCB.

Control of Rhyzopertha dominica in stored rough rice through a combination of diatomaceous earth and varietal resistance

Adults ofRhyzopertha dominica （F.）, the lesser grain borer, were exposed on four varieties of rough rice with Dobie indices of susceptibility of 1.1 to 1.1 （low）, and four varieties with Dobie indices of susceptibility of 3.4 to 3.8 （high）. The varieties with low and high Dobie indices were classified as resistant and susceptible, respectively, to R. dominica. The purpose of the study was to evaluate control of R. dominica through the use of diatomaceous earth （DE） in combination with rice varieties that were either susceptible or resistant to R. dominica. The rice was treated with varying rates of the commercial DE Insecto, up to a maximum of 1 000 mg DE/kg of rice. Adult mortality at each application rate of DE was generally greater on three of four resistant varieties compared to three of four susceptible varieties. Progeny production from the parental generation exposed on the rice was also greater in 3 of the 4 resistant varieties compared to 3 of the 4 susceptible varieties at DE rates of 500 mg/kg or more. Progeny production in rice treated with a maximum rate of 1 000 mg/kg DE ranged from 7-44 adults on the resistant varieties compared to 75-155 adults on the susceptible varieties. At DE rates of 500, 750, and 1 000 mg/kg, the percentage of insect-damaged kernels （IDK） was also greater in 3/4 resistant varieties than in the susceptible varieties. Results show combining the use of DE with varietal resistance of rough rice to R. dominica could be used to limit populations of this insect in stored rice and help prevent economic damage.

Resistance of stored bean varieties to Acanthoscelides obtectus （Coleoptera： Bruchidae）

During bean seed storage, yield can be lost due to infestations of Acanthoscelides obtectus Say, the bean weevil. The use of resistant varieties has shown promising results in fighting these insects, reducing infestation levels and eliminating chemical residues from the beans. The expression of resistance to A. obtectus in bean varieties is frequently attributed to the presence of phytohemagglutinins, protease inhibitors and alpha-amylase, and especially to variants of the protein arcelin, which reduce the larval viability of these insects. To evaluate the effect of bean seed storage time on the resistance expression of bean varieties to A. obtectus, tests with seeds of three ages （freshly-harvested, 4-month-old, and 8-monthold） were conducted in the laboratory, using four commercial varieties： Carioca Pitoco, Ipa 6, Porrillo 70, Onix; four improved varieties containing arcelin protein： Arc. 1, Arc.2, Arc. 3, Arc.4; and three wild varieties also containing arcelin protein： Arc.lS, Arc.3S, and Arc. 5S. The Arc.5S, Arc.lS, and Arc.2 varieties expressed high antibiosis levels against the weevil; Arc.1 and Arc3S expressed the same mechanism, but at lower levels. The occurrence of oviposition non-preference was also observed in Arc.5S and Arc. 1S. The Arc.3 and Arc. 4 varieties expressed low feeding non-preference levels against A. obtectus. The expression of resistance in arcelin-bearing, wild or improved varieties was affected during the storage of seeds, and was high under some parameters but low in others. The results showed that addition of chemical resistance factors such as protein arcelin via genetic breeding may be beneficial in improving the performance of bean crops.

Flavonoid-producing tomato plants have a direct negative effect on the zoophytophagous biological control agent Oriussauteri

Orius sauteri(Poppius)(Hemiptera:Anthocoridae)is often used for biological control of small arthropod pests in greenhouse vegetable production systems in Asia.In addition to feeding on arthropod prey,O.sauteri consumes small quantities of plant material.Previous studies demonstrated that tomato plant chemistry confers antixenosis resistance to phloem-feeding whiteflies,but the potential nontarget effects of phytochemicals on the beneficial predator O.sauteri are unknown.Comparison of O.sauteri confined to near-isogenic lines(NILs)of tomatoes producing high levels offlavonoids(NIL-purple hypocotyl;resistant to whiteflies)and low levels of flavonoids(NIL-green hypocotyl;susceptible to whiteflies)revealed that O.sauteri had reduced oviposition,nymphal survival,and development on resistant plants,even if they were also provided with prey that did not feed on the host plant.Moreover,O.sauteri showed a significant ovipositional preference in choice assays,laying significantly more eggs on susceptible than on resistant plants.Molecular gut content analysis using the specific chloroplast trnL gene from tomato confirmed that adult and immature O.sauteri feed on both resistant and susceptible genotypes,and feeding behavior assays revealed that resistance did not affect plant feeding or prey acceptance by O.sauteri adults.These results demonstrate a direct negative effect of phytochemicals on a nontarget beneficial species and indicate that resistance mediated by phytochemicals can affect organisms that do not solely feed on phloem sap.The results also indicate that the mode of action and the potential ecological effects of phytochemicalmediated resistance are broader than previously recognized.

Drought Stress and Preharvest Aflatoxin Contamination in Agricultural Commodity: Genetics, Genomics and Proteomics

Throughout the world, aflatoxin contamination is considered one of the most serious food safety issues concerning health. Chronic problems with preharvest afiatoxin contamination occur in the southern US, and are particularly troublesome in corn, peanut, cottonseed, and tree nuts. Drought stress is a major factor to contribute to preharvest afiatoxin contamination. Recent studies have demonstrated higher concentration of defense or stress-related proteins in corn kerners of resistant genotypes compared with susceptible genotypes, suggesting that preharvest field condition （drought or not drought） influences gene expression differently in different genotypes resulting in different levels of ＂end products＂： PR（pathogenesis-related） proteins in the mature kernels. Because of the complexity of Aspergillus-plant interactions, better understanding of the mechanisms of genetic resistance will be needed using genomics and proteomics for crop improvement. Genetic improvement of crop resistance to drought stress is one component and will provide a good perspective on the efficacy of control strategy. Proteomic comparisons of corn kernel proteins between resistant or susceptible genotypes to Aspergillus flavus infection have identified stress-related proteins along with antifungal proteins as associated with kernel resistance. Gene expression studies in developing corn kernels are in agreement with the proteomic studies that defense-related genes could be upregulated or downregulated by abiotic stresses.

A virus-derived siRNA activates plant immunity by interfering with ROS scavenging

Virus-derived small interference RNAs(vsiRNAs)not only suppress virus infection in plants via induction of RNA silencing but also enhance virus infection by regulating host defensive gene expression.However,the underlying mechanisms that control vsiRNA-mediated host immunity or susceptibility remain largely unknown.In this study,we generated several transgenic wheat lines using four artificial microRNA expression vectors carrying vsiRNAs from Wheat yellow mosaic virus(WYMV)RNA1.Laboratory and field tests showed that two transgenic wheat lines expressing amiRNAI were highly resistant to WYMV infection.Further analyses showed that vsiRNAI could modulate the expression of a wheat thioredoxin-like gene(TaAAEDI),which encodes a negative regulator of reactive oxygen species(ROS)production in the chloroplast.The function of TaAAEDI in ROS scavenging could be suppressed by vsiRNAI in a dose-dependent manner.Furthermore,transgenic expression of amiRNAI in wheat resulted in broad-spectrum disease resistance to Chinese wheat mosaic virus,Barley stripe mosaic virus,and Puccinia striiformis f.sp.tritici infection,suggesting that vsiRNAI is involved in wheat immunity via ROS signaling.Collectively,these findings reveal a previously unidentified mechanism underlying the arms race between viruses and plants.

Response of life-history traits to artificial and natural selection for virulence and nonvirulence in a Drosophila parastitoid, Asobara tabida

Co-evolution of host-parasitoid interactions is determined by the costs of host resistance, which received empirical evidence, and the costs ofparasitoid virulence, which have been mostly hypothesized. Asobara tabida is a parasitoid, which mainly parasitizes Drosophila melanogaster and D. subobscura, the first species being able to resist to the parasitoid development while the second species is not. To parasitize resistant hosts, including D. melanogaster, A. tabida develops sticky eggs, which prevent encapsulation, but this virulence mechanism may be costly. Interindividual and interpopulation variation in the proportion of sticky eggs respectively allowed us to （i） artificially select and compare life-history traits of a virulent and a nonvirulent laboratory strain, and （ii） compare a virulent and a nonvirulent field strain, to investigate the hypothetical costs of virulence. We observed strong differences between the 2 laboratory strains. The nonvirulent strain invested fewer resources in reproduction and walked less than the virulent one but lived longer. Concerning the field strains, we observed that the nonvirulent strain had larger wings while the virulent one walked more and faster. All together, our results suggest that virulence may not always be costly, but rather that different life histories associated with different levels of virulence may coexist at both intra- and interDoDulation levels.