Insecticide resistance of the field populations of oriental armyworm,Mythimna separata (Walker) in Shaanxi and Shanxi provinces of China

Resistance of five field populations of Mythimna separata(Walker) collected from Shaanxi and Shanxi provinces of China to six different insecticides was evaluated by leaf dip method in the laboratory. The results showed that all populations were relatively sensitive to emamectin benzoate with a resistance ratio(RR) of 0.583–1.583 folds. All populations showed susceptible or low level resistance to chlorantraniliprole and beta-cypermethrin. Compared with a relatively susceptible strain of M. separata, the resistance level of the whole populations ranged from susceptible to moderate to chlorpyrifos and lambda-cyhalothrin, moderate to high to phoxim(RR=19.367–70.100) except for population from Sanyuan County(RR=2.567). Pair-wise correlation analysis among different insecticides indicated that chlorpyrifos has a significantly positive and significant correlation with emamectin benzoate. Chlorantraniliprole didn't have significant correlation with emamectin benzoate, chlorpyrifos and phoxim. Therefore, emamectin benzoate, chlorantraniliprole and beta-cypermethrin are recommended to control oriental armyworm. Meanwhile, to postpone the occurrence and development of insecticide resistance in Shaanxi and Shanxi provinces, alternative and rotational application of insecticides between chlorantraniliprole and emamectin benzoate or chlorpyrifos is necessary.     

Insecticide resistance monitoring for the invasive populations of fall armyworm,Spodoptera frugiperda in China

Fall armyworm has invaded China and colonized its populations in tropical and sub-tropical regions of South China since December 2018. Chemical spray has been widely used to control the pest, which shall lead to resistance evolution. In this research, we collected five populations of the pest from Yunnan, Hainan, Tibet, and Fujian of China, and tested their susceptibilities to pyrethroid, organophosphorus, oxadiazine, diamide, antibiotics and other types of insecticides(14 insecticides totally) in the laboratory. Based on the susceptible baseline published from the previous studies, the resistance ratio was 615–1 068-fold to chlorpyrifos, 60–388-fold to spinosad, 26–317-fold to lambda-cyhalothrin, 13–29-fold to malathion, 9–33-fold to fenvalerate, 8–20-fold to deltamethrin, 3–8-fold to emamectin benzoate and 1–2-fold to chlorantraniliprole, respectively. The median lethal concentration(LC_(50)) of other six insecticides without the susceptible baselines was 148.27–220.96 μg mL~(–1) for beta-cypermethrin, 87.03–128.43 μg mL~(–1) for chlorfenapyr, 16.35–99.67 μg mL~(–1) for indoxacarb, 10.55–51.01 μg mL~(–1) for phoxim, 7.08–8.78 μg mL~(–1) for M-EBI(the mixed insecticide of emamectin benzoate and indoxcarb) and 1.49–4.64 μg mL~(–1) for cyantraniliprole. This study can be helpful for chemical control as well as for resistance monitoring and management of the pest in China.     

Two-way predation between immature stages of the hoverfly Eupeodes corollae and the invasive fall armyworm(Spodoptera frugiperda J. E. Smith)

Since its 2018 invasion of eastern Asia, the fall armyworm Spodoptera frugiperda(Lepidoptera: Noctuidae) has become a key pest in local maize production. Though pesticides have been widely used to mitigate the initial S. frugiperda attack, biological control is receiving ample attention as a desirable, environmentally-sound alternative to chemical control. Hoverflies(Diptera: Syrphidae) are abundant natural enemies in Chinese maize fields and have been observed to consume S. frugiperda larvae. In this study, we use laboratory assays to study the two-way interaction between immature stages of S. frugiperda and the endemic syrphid Eupeodes corollae. To mimic natural conditions, assays were performed in the presence of fresh maize leaves. Those 2 nd or 3 rd instar larvae of E. corollae preyed on 1 st and 2 nd instar S. frugiperda larvae with a Holling type III response, consuming a respective theoretical maximum of 43.48 and 83.33 larvae over a 24-h period. Conversely, once S. frugiperda larvae reached 3 rd instar, they exhibited aggressive behavior and equally preyed on syrphid larvae with a Holling type III response. Those 5 th and 6 th instar larvae of S. frugiperda consumed a respective 16.39–19.23, 6.02–19.61 and 6.76–8.26 of 1 st, 2 nd and 3 rd instar E. corollae larvae per day. Though our results await field-level validation, S. frugiperda agonistic(i.e., defensive) and consumptive behavior towards resident natural enemies such as E. corollae possibly degrades biotic resistance and raises its invasion potential. Our findings shine new light on the interaction between lepidopteran herbivores and their natural enemies, and can help advance the development of conservation biological control and other integrated pest management(IPM) strategies against S. frugiperda in China and abroad.     

Effects of Terpinen-4-ol on Four Metabolic Enzymes and Polyphenol Oxidase （PPO） in Mythimna separta Walker

To study insecticidal mechanism of terpinen-4-ol, a main insecticidal composition in the essential oil of Sabina vulgaris, the 5th instar larvae of Mythimna separta, were investigated with terpinen-4-ol by topical application. The activities of phosphatase, glutathione S-transferase （GSTs）, cytochrome P450 （P450）, and polyphenol oxidase （PPO） of tested insects were determined in all poisoning stages, including exciting stage, convulsing stage, paralysis stage, and recover stage. The result showed that the activities of both acid phosphatase （ACP） and alkaline phosphatase （AKP） in treated insects were induced by terpinen-4-ol, but ACP was inhibited in paralysis stage. The activities of GSTs were inhibited in exciting stage, convulsing stage, and paralysis stage, but gradually recovered in recover stage. O-demethylase activity of cytochrome P450 was inhibited by terpinen-4-ol, and the inhibition rate in all poisoning stages were 26.27, 46.03, 80.24, and 90.22%, respectively. PPO activities were strongly inhibited by terpinen-4-ol both in vitro and in vivo. In conclusion, the activities of P450, GSTs, and PPO could have relation with toxicity of terpinen-4-ol against larvae of the Mythimna separta, but recover stage of the poisoning insects might be related to GSTs induced. As a new insecticide or synergist, terpinen- 4-ol has a potential value in field of insecticide resistance management.     

Susceptibility of Ostrinia furnacalis to Bacillus thuringiensis and Bt Corn Under Long-Term Laboratory Selection

The susceptibility of the Asian corn borer, Ostriniafurnacalis to Bacillus thuringiensis (Bt) formulation and Bt corn was evaluated using insect bioassays for 6 years. Four strains of O. furnacalis were developed by laboratory selection from the laboratory strain reared on a non-agar semi-artificial diet. The RR-1 strain was exposed to a commercial formulation of B. thuringiensis subsp, kurstaki (Btk) incorporated into the artificial diet, the RR-2 strain was exposed to Bt corn (MON810)tissue incorporated into the diet, and the SS-1 and SS-2 strains were reared on the standard diet with or without non-Bt corn tissues material. Decreasing susceptibility of O. furnacalis to Bt and to Bt corn were found in each selected strain although the EDs0 and larval weight fluctuated from generation to generation. The resistance of Bt-exposed strain (RR-1)to Btk increased 48-fold by generation 39; the Bt corn-exposed strain (RR-2) increased its resistance 37-fold to Btk by generation 24. No larvae of SS- 1 survived when they were exposed to the leaves of Bt corn, Bt 11 and MON810. However,2-54% of the RR-1 (generation 46) and RR-2 (generation 20) larvae survived a 3 day-exposure to the leaves of Btl 1 and MON810. The survival of both selected strains on Bt corn silk increased by 10-69%, and the larval weights after many generations selection were increased by 15-22% compared with the unselected susceptible strain. The young larvae were much more susceptible to Bt than older larvae. The highest mortality occurred when the larvae were exposed to Bt at the neonate stage. All of the results suggested that ACB could not only develop resistance to Bt preparation but also to Bt corn. Bt had significant effects on the growth and development of Asian corn borer than on the larval mortality. In order to maintain the long-term effectiveness of Bt pesticide and Bt corn, the resistance management should pay much attention to the larvae that may have opportunities to grow and developed on non-Bt corn or alternate hosts before they attack the Bt corn plants and the survival of larvae after Bt application.     

Effect of Rapid Cold Hardening on the Cold Tolerance of the Larvae of the Rice Stem Borer,Chilo suppressalis （Walker）

The effects of rapid cold hardening （RCH） on the cold tolerance of the last instar larvae of Chilo suppressalis （Walker） were evaluated for the first time. The discriminating temperature, induction, detection, duration and extent of RCH of the larvae in the laboratory were tested, and the supercooling points （SCPs） and the contents of water and lipid of the larvae after RCH treatment were determined, respectively. The results showed that the discriminating temperature of the larvae was about -21℃. Mean survival rates of the larvae which exposed to either 0 or 5℃ for 2 and 4 h before exposure to the discriminating temperature for 2 h were significantly higher than those of the control groups （P 〈 0.05）. Moreover, the highest survival rate appeared in the larvae after 0℃ for 4 h treatment. The protection against low temperature gained by RCH at 0℃ for 4 h was rapidly lost on return to 28℃. Mean survival rates of RCH larvae were significantly higher than those of non-acclimated （NACC） larvae and acclimation （ACC） larvae when they were exposed to the discriminating temperature for 2 or 4 h （P〈 0.05）. Moreover, the rates of NACC, ACC, RCH and ACC ＋ RCH larvae from 2 to 6 h to the discriminating temperature resulted in a significant decline. The values of SCPs and the contents of lipid of the larvae which exposed to either 0 or 5℃ for 2 and 4 h showed no significant difference at 0.05 level compared to those of the control groups. But the contents of water in the larvae were obviously decreased. Therefore, it could be concluded that RCH could enhance cold tolerance and affect partly physiological and biochemical components of the larvae of C. suppressalis, but the underlying mechanisms needs to be further explored.     

Genetic Diversity of Maize Populations Developed by Two Kinds of Recurrent Selection Methods Investigated with SSR Markers

Two cycles of biparental mass selection （MS） and one cycle of half-sib-S3 family combining selection （HS-S3） for yield were carried out in 2 synthetic maize populations P4C0 and P5C0 synchronously. The genetic diversity of 8 maize populations, including both the basic populations and their developed populations, were evaluated by 30 SSR primers. On the 30 SSR loci, a total of 184 alleles had been detected in these populations. At each locus, the number of alleles varied from 2 to 14, with an average of 6.13. The number and ratio of polymorphic loci in both the basic populations were higher than those of their developed populations, respectively. There was nearly no difference after MS but decreased after HS-S3 in both the basic populations in the mean gene heterozygosity. The mean genetic distance changed slightly after MS but decreased in a bigger degree after HS-S3 in both the basic populations. Analyses on the distribution of genetic distances showed that the ranges of the genetic distance were wider after MS and most of the genetic distances in populations developed by HS-S3 were smaller than those in both the basic populations. The number of genotypes increased after MS but decreased after HS-S3 in both the basic populations. The genetic diversity of intra-population was much more than genetic diversity of inter-population in both the basic populations. All these indexes demonstrated that the genetic diversity of populations after MS was similar to their basic populations, and the genetic diversity was maintained during MS, whereas the genetic diversity of populations decreased after HS-S3. This result indicated that heterogeneity between some of the individuals in the developed populations increased after MS, whereas the populations become more homozygotic after HS-S3.     

Effect of Exogenous MJA Treatment of Tea Plants on the Growth of Geometrid Larvae

The effect of tea plant Camellia sinensis induced by exogenous methyl jasmonate （MJA） on lipoxygenase （LOX）, polyphenol oxidase （PPO） and proteinase inhibitor （PI） activity in the leaves of tea plants, as well as the growth and midgut proteinase activity of the geometrid Ectropis obliqua larvae were studied. MJA significantly induced LOX, PPO and PI activity in leaves of tea plants. When geometrid larvae have fed on leaves of tea plants treated with MJA, the activities of the high alkaline trypsin-like enzyme and chymotrypsin-like enzyme in their midgut were significantly inhibited, but the activities of the low alkaline trypsin-like enzyme in their midgut were unaffected, leading to imbalance between different types of proteinase activity in the midgut of the larvae and in turn, the growth were inhibited. These chains of response may be an important mechanism of the direct resistance induced by MJA-treatment of tea plant on geometrid larvae.     

Spatio-temporal relationships of Clania miniscula （Lepidoptera： Psychidae） and garden spider （Araneae： Araneidae） in sasanqua orchard

Spatio-temporal relationship of the phytophagons Clania miniscula （Butler） and garden spiders was examined through analysis of their niche and distribution as they occur in sasanqua orchard in Southern Anhui, China from June 2003 to May 2004. The dynamic relationships between Clania minuscula and garden spiders were seasonal in time and space. Spatio-temporal niche breadth was high for the two groups, ranging from 0.57 to 0.98; niche overlap was also high between the two groups from 0.76 to 0.96 during the seasons of June 2003 to May 2004. Geostatistical results indicated that Clania minuscula and garden spiders were aggregated during the emergence periods. The pest Clania minuscula was spatially dependent to a range from 33.48 to 46.84 m while spatial dependence from 30.93 to 51.11 m for garden spiders. The correlation analysis of distribution maps further illustrate the distribution of garden spiders always coincided with that of Clania minuscula. These results showed spatio-temporal synchrony of Clania minuscula and garden spiders at different periods. Adequate knowledge of spatio-temporal correlation between Clania minuscula and garden spiders contributed to provide information for biocontrol at different periods in sasanqua orchard.     

Comparative Analyses of Proteome Complement Between Worker Bee Larvae of High Royal Jelly Producing Bees （A. m. ligustica） and Carniolian Bees （A. m. camica）

This study is to compare the protein composition of the high royal jelly producing bee （A. m. ligustica） with that of Carniolian bee （A. m. carnica） during their worker larval developmental stage. The experiment was carried out by two- dimensional gel electrophoresis. The results showed that significant higher numbers of total proteins （283） were detected in larvae of high royal jelly producing bees （Jelly bee） than those of Carniolian bees （152） on 2-d-old larvae. Among them, 110 proteins were presented on both strains of bee larvae, whereas 173 proteins were specific to larvae of Jelly bees, and 42 proteins were exclusive to Carniolian larvae. However, on the 4th d, a significant higher number of total proteins （290） were detected in larvae of Jelly bees than those of Carniolian bees （240）, 163 proteins resolved to both bee larvae, and 127 proteins were specific to Jelly bees and 77 proteins to Camiolian bees. Until the 6th d, also a significant higher number of total proteins （236） were detected in larvae of Jelly bees than those of Carniolian bees （180）, 132 proteins were constantly expressed in two bee larvae, whereas 104 and 48 proteins are unique to Jelly bee and Carniolian bee larvae, respectively. We tentatively concluded that the metabolic rate and gene expression of Jelly bees larvae is higher than those of Carniolian bees based proteins detected as total proteins and proteins specific to each stage of two strains of bee larvae. Proteins constantly expressed on 3 stages of larval development with some significant differences between two bee strains, and proteins unique to each stage expressed differences in term of quality and quantity, indicating that larval development needed house keeping and specific proteins to regulate its growth at different development phage, but the expression mold is different between two strains of larval development.     

Comparing the Impact of a Neonicotinoid and Biorational Agroneem on Herbivorous and Beneficial Arthropods on Cowpea and Tomato

Cowpea （Vigna unguiculata L. Walp.） and tomato （Lycopersicum esculentum L. Karst） are attacked by a wide range of insect pests worldwide. In many cases, pesticides are used to control the pests. In 2010 and 2011, we conducted field experiments to evaluate and compare the effectiveness of a biorational （Agroneem~） and conventional pesticide （imidacloprid or thiamethoxam） on insect pests of these crops. In the first year, two varieties of cowpea （Mississippi Silver and Pinkeye Purple Hull） and two of tomato （Mariana and German Johnson） were used; in the second year, the better performing of each group （Mississippi Silver and Mariana） were used for the study. A split-plot design with four replications in Year 1, and a randomized complete block design with six treatment combinations in Year 2. In the first year, both pesticide groups were applied following manufacturer＇s recommendation （10-14 d cycles）; and in the second year, the application of the pesticides was driven by economic thresholds level （ETL） of insect pests. The most prevalent species of insects recorded in both crops were in the families： Chrysomelidae, Pentatomidae, Cicadellidae, Vespidae, Sarcophagidae, Thripidae and Sphingidae. In both years, the diversity of insects on cowpea was greater than on tomato and more insects were observed in the second year compared to the first, despite the absence of significant difference （P 〉 0.05） between varieties in the treated plots. The yield of cowpea and tomato was comparable in all sprayed plots.     

Corn Yield Forecasting in Northeast China Using Remotely Sensed Spectral Indices and Crop Phenology Metrics

Early crop yield forecasting is important for food safety as well as large-scale food related planning. The phenology-adjusted spectral indices derived from Moderate Resolution Imaging Spectroradiometer （MODIS） data were used to develop liner regression models with the county-level corn yield data in Northeast China. We also compared the different spectral indices in predicting yield. The results showed that, using Enhanced Vegetation Index （EVI）, Normalized Difference Water Index （NDWI） and Land Surface Water Index （LSWI）, the best time to predict corn yields was 55-60 days after green-up date. LSWI showed the strongest correlation （R2=0.568）, followed by EVI （R2=0.497） and NDWI （R2=0.495）. The peak correlation between Wide Dynamic Range Vegetation Index （WDRVI） and yield was detected 85 days after green-up date （RZ=0.506）. The correlation was generally low for Normalized Difference Vegetation Index （NDVI） （R2=0.385） and no obvious peak correlation existed for NDVI. The coefficients of determination of the different spectral indices varied from year to year, which were greater in 2001 and 2004 than in other years. Leave-one-year-out approach was used to test the performance of the model. Normalized root mean square error （NRMSE） ranged from 7.3 to 16.9% for different spectral indices. Overall, our results showed that crop phenology-tuned spectral indices were feasible and helpful for regional corn yield forecasting.     

Effect of Transgenic Corn Cultivation and Sampling Location on Feeding Habits of Collembola

Transgenic corn was modified to combat lepidopteran pests, herbicide and other deteriorate environmental factors. However, fewer studies concerned the effects of transgenic corn cultivation on the soil Collembola in black soil region in China. In Jilin black soil region, a six treatments study including three corn varieties （transgenic corn, control and local variety） and two sampling locations （in rizhosphere and in between plants） were deployed to study the effect of transgenic corn cultivation and sampling location on densities, species richness and community structure of Collembola. We found that root biomass was marginally decreased in transgenic corn and control variety when compared to local variety. Collembola significantly affected by sampling location treatments. Densities and species richness of collembolans significantly decreased in ＂between plants＂ than in ＂rizhosphere＂. Densities of Collembola were impacted by corn varieties. In the whole growing season, densities of Collembola significantly decreased in control than in local variety. Collembolans in transgenic variety only slightly decreased in ＂jointing stage＂ than local variety. Collembolans adversely affected in ＂between plants＂ when compared to ＂in rhizosphere＂ in ＂seeding stage＂ but not other stages. These variations of collembolans were in lines with the trend of corn root biomass. It is indicated that Collembola variations could be caused by food resources （root biomass） but not corn varieties （transgenic, control and local）.     

Comparative Studies of Substrate and Inhibitor Specificity of Glutathione S-Transferases in Six Tissues of Oxya chinensis （Thunberg） （Orthoptera： Acrididae）

Specific activity, substrate specificity, and kinetic parameters （Km and Vmax） of glutathione S-transferases （GSTs） towards three substrates, 1-chloro-2,4-dinitrobenzene （CDNB）, 1,2-dichloro-4-nitrobenzene （DCNB）, and p-nitrobenzene chloride （pNBC） were investigated in six tissues （foregut, midgut, hindgut, fat body, hemolymph, and muscle） of Oxya chinensis. In addition, the inhibition in vitro （ethacrynic acid, and Cibacron Blue 3GA） of Oxya chinensis in the six tissues was also investigated. Glutathione S-transferase activity was detected in all the six tissues examined. The rank order of GST activities towards CDNB was fat body 〉 midgut 〉 hindgut 〉 muscle 〉 foregut 〉 hemolymph both in females and males. Glutathione S-transferase activities in the fat body in females and males were 1.3- to 10.4-fold and 1.1- to 10.0- fold higher than those in the other tissues. The rank order of GST activities towards the other substrates changed slightly. From these results, it was inferred that GSTs in the fat body and midgut played important roles in detoxifying xenobiotics including insecticides and plant allelochemicals in O. chinensis. In the three substrates examined, CDNB seemed to be the best substrate, followed by pNBC and DCNB. The kinetic parameters of GSTs were different among the six tissues. This suggested that GSTs in different tissues have various affinities and catalytic efficiency to substrates. In vitro inhibition study showed that the median inhibition concentration （IC50） values of the two inhibitors to GSTs from the six tissues were different. The results suggested that the two inhibitors have different inhibition potency to GSTs from the different tissues. The observed changes in kinetic parameters and inhibition in vitro among the six tissues of the insect might suggest that the number and structure of isoenzymes and their rate of expression varied for the different tissues.     

Efficiency of Different Methods for dsRNA Delivery in Cotton Bollworm （Helicoverpa armigera）

RNAi trigged by dsRNA not only facilitates the development of molecular biology, but also initiates a new way for pest control by silence of fatal genes. However, one of the key limitations in pest control is lack of the convenient and efficient method for dsRNA delivery. In this study, different dsRNA delivery methods at their own optimum conditions were evaluated comparatively for their efficiency with Helicoverpa armigera as test animal. It was found that the popular one- time injection of larvae with dsRNA could reduce the pupation rate by 43.0% and enhance larva mortality by 11.7%. One- time ingestion of dsRNA did not result in any significant effect on phenotype. Continuous ingestion of in vitro synthesized dsRNA by refreshing the bait diet every day caused 40.4% decrease in successful pupation and 10.0% increase in larval mortality, which was similar as one-time injection. The most efficient method was found to be the continuous ingestion of the bacteria containing dsRNA expressed, which reduced the rate of pupation by 68.7% and enhanced the larval mortality by 34.1%. Further analysis found that dsRNA was degraded faster in midgut juice than in hemolymph. However, the cell of bacteria could protect dsRNA and delay the degradation in the midgut juice of H. armigera. These results throw light on the application of dsRNA in pest management with proper ways.     

Mathematical Modeling and Effect of Various Hot-Air Drying on Mushroom （Lentinus edodes）

An experimental study was performed to determine the characteristics and drying process of mushroom （Lentinus edodes） by 6 different hot-air drying methods namely isothermal drying, uniform raise drying, non-uniform raise drying, uniform intermittent drying, non-uniform intermittent drying and combined drying. The chemical composition （dry matter, ash, crude protein, crude fat, total sugars, dietary fiber, and energy）, color parameters （L, a＊, b＊, c＊, and h~） and rehydration capacities were determined. Among all the experiments, non-uniform intermittent drying reached a better comprehensive results due to the higher chemical composition, better color quality associated with high bright （26.381＋5.842）, high color tone （73.670＋2.975）, low chroma （13.349a：3.456） as well as the highest rehydration （453.76% weigh of dried body）. Nine kinds of classical mathematical model were used to obtained moisture data and the Midili-kucuk model can be described by the drying process with the coefficient （R2 ranged from 0.99790 to 0.99967）, chi-square （X2 ranged from 0.00003 to 0.00019） and root mean square error （RMSE ranged from 0.000486 to 0.0012367）.     

Long Chain Acyl-Coenzyme A Synthetase 4 （BnLACS4） Gene from Brassica napus Enhances the Yeast Lipid Contents

Long-chain acyl-Coenzyme A （CoA） synthetases （LACSs） catalyze the formation of long-chain acyl-CoA, and play important roles in fatty acid metabolism including phospholipids, triacylglycerol （TAG） biosynthesis and fatty acid 13-oxidation. Here, we report the characterization of a LACS gene from Brassica napus. It is highly homologous to Arabidopsis LACS4 and thus designated as BnLACS4. The cloned gene BnLACS4 could complement a LACS-deficient yeast strain YB525. It is mainly expressed in flowers and developing seeds where lipid biosynthesis is at high rate in Brassiea napus. When transiently expressed in tobacco leaves, BnLACS4 is localized in endoplasmic reticulum （ER）, the common site for eukaryotic pathway of lipid biosynthesis. Expression of BnLACS4 in the yeast strain pep4 increased its lipid content. Taken together, our results suggest that BnLACS4 may be involved in lipid biosynthesis in B. napus.     

Effects of Various Doses of Mineral Fertilizers (NPKS and Urea) on Yield and Economic Profitability of New Varieties ofZea mays L. in Faranah,Guinea

In Faranah Province(Guinea), the ratio of supply and demand of corn is approximately 1 : 2. The production is low and the deficit is covered by maize importation. This study was initiated in order to improve corn production by evaluating the effects of increasing doses of mineral fertilizers on the yield and economic profitability of corn. The experiment was conducted on a farm in Kamedankoude in a split plot with three replicates. Treatments included two varieties of maize(Perta and Kilissi113) and five doses of chemical fertilizers(D0=unfertilized control, D1=300 kg NPKS+200 kg urea · hm~(-2); D2=400 kg NPKS+800 kg urea · hm~(-2); D3=200 kg NPKS+400 kg urea-· hm~(-2) and D4=500 kg NPKS+600 kg urea · hm2). The results showed that all the agronomic parameters increased with increasing dose of fertilizers, except for the number of ears per plant. The two varieties of corn tested produced similar yields. However, the profitability of mineral fertilizers decreased with increased doses and with value/cost ratio of 3. We recommended a mineral fertilizer dose of 300 kg NPKS + 200 kg urea. The high prices of mineral fertilizers were often barriers to intensive maize cultivation, especially for low-income farmers. This study was a contribution to rational fertilization and adapted the socio-economic conditions of the region, with the background knowledge that most farmers in the regions earned low incomes.     

Co-Treatment of EFF and 1-MCP for Enhancing the Shelf-Life and Aroma Volatile Compounds of Oriental Sweet Melons （Cucumis melo var. makuwa Makino）

Compared to other melon types, oriental sweet melon （Cucumis melo var. makuwa Makino） is quite a different species with a shorter shelf-life due to its typical climacteric behavior and thin pericarp. The purpose of this experiment is to explore the effects of co- treatment of enhanced freshness formulation （EFF） and 1-methylcyclopropene （1-MCP） on physiological changes and the content of aroma volatile compounds introduced by them of two oriental sweet melon cultivars （Yumeiren and Tianbao） during storage. The melons were stored in incubators with temperature of 15~C and a relative humidity of 85% for 24 d during which fruit quality and related physiological index were measured. Compared to the control, both treatments delayed fruit weight loss rate and kept the fruit firmness, water content and soluble solids content. Ascorbate peroxidase （APX） and phenylalanine ammonia lyase （PAL） activities showed fluctuations in treated melons, while lipoxygenase （LOX） activity （P〈0.01） and malondialdehyde （MDA） content （P〈0.05） decreased compared to control. During the early stage of storage, alcohols and aldehydes were the main volatile compounds, and esters gradually increased during storage. Of all the esters, acetic esters were the main components, followed by oxalic acid esters and other esters. The total content of aroma volatile compounds, esters, alcohols and aldehydes of co-treated melons were all higher than those of 1-MCP treated and control melons. In addition, the aroma volatile peak of co-treated melons occurred later than that of 1-MCP treated and control melons. In summary, co-treatment of EFF and 1-MCP was more beneficial than 1-MCP treatment to delay ripening and senescence, maintain fruit quality, enhance shelf-life and improve levels of aroma volatile compounds.     

玉米弯孢菌叶斑病空间旋转模型(GRSM)

模型z=f(x)或z=f(y)绕 z 轴旋转,得到空间对称模型z=f(x2+y2)0.5)及不对称模型z=f(ax2+by2)0.5),其中x,y是空间距离.这些空间旋转模型可以反映玉米弯孢茵叶斑病空间发展情况,同时通过SAS软件模拟得到掖单13和海试16上的较优空间分布模型.同时解释田间不同气候条件下,该病害出现对称和不对称分布模式的原因.