Comparative transcriptional analysis provides insights of possible molecular mechanisms of wing polyphenism induced by postnatal crowding in Aphis gossypii

Background
Aphis gossypii is a worldwide sap-sucking pest with a variety of hosts and a  vector of more than 50 plant viruses. The strategy of wing polyphenism, mostly resulting from population density increasing, contributes to the evolutionary success of this pest. However, the related molecular basis remains unclear. Here, we identified the effects of postnatal crowding on wing morph determination in cotton aphid, and examined the transcriptomic differences between wingless and wing morphs.

Results
Effect of postnatal crowding on wing determination in A. gossypii was evaluated firstly. Under the density of 5 nymphs·cm− 2, no wing aphids appeared. Proportion of wing morphs rised with the increase of density in a certain extent, and peaked to 56.1% at the density of 20 nymphs·cm− 2, and reduced afterwards. Then, transcriptomes of wingless and wing morphs were assembled and annotated separately to identify potentially exclusively or differentially expressed transcripts between these two morphs, in which 3 126 and 3 392 unigenes annotated in Nr (Non-redundant protein sequence) database were found in wingless or wing morphs exclusively. Moreover, 3 187 up- and 1 880 down-regulated genes were identified in wing versus wingless aphid. Pathways analysis suggested the involvement of differentially expressed genes in multiple cellular signaling pathways involved in wing morphs determination, including lipid catabolic and metabolism, insulin, ecdysone and juvenile hormone biosynthesis. The expression levels of related genes were validated by the reverse transcription quantitative real time polymerase chain reaction (RT-qPCR) soon afterwards.

Conclusions
The present study identified the effects of postnatal crowding on wing morphs induction and demonstrated that the critical population density for wing morphs formation in A. gossypii was 20 nymphs·cm− 2. Comparative transcriptome analysis provides transcripts potentially expressed exclusively in wingless or wing morph, respectively. Differentially expressed genes between wingless and wing morphs were identified and several signaling pathways potentially involved in cotton aphid wing differentiation were obtained.

Authors:

JI Jichao, ZHANG Shuai, LUO Junyu, WANG Li, ZHU Xiangzhen, ZHANG Kaixin, ZHANG Lijuan & CUI Jinjie

Journal of Cotton Research. 2019,2:17

https://doi.org/10.1186/s42397-019-0036-z

Amino acids application enhances flowers insecticidal protein content in Bt cotton

[Background] Low insecticidal protein expression at reproductive organs affect insect resistance in Bt transgenic cotton. In order to enhance flower insecticidal protein expression, the conventional cultivar Sikang1 (S1) and the hybrid cultivar Sikang3 (S3) were used as experimental materials; the applications of selected 5 types of amino acids and 21 types of amino acids were sprayed on the flowers in 2016 and 2017 cotton growing seasons.

[Results] The flower Bt protein contents increased significantly under the two amino acid treatments in both cultivars, the Bt protein concentration increased by 15.2 to 25.8% compared with the control. However, no significant differences were detected between the two treatments of amino acid application. Increased amino acid and soluble protein contents, enhanced GPT, GOT, protease,and peptidase activities were observed under the amino acid application at the flowering stage.

[Conclusions] These results suggest that exterior application of the amino acids treatments could bolster the flower insecticidal protein expression.

[Authors] TAMBEL Leila. I. M., ZHOU Mingyuan, CHEN Yuan, ZHANG Xiang, CHEN Yuan  and CHEN Dehua

Journal of Cotton Research. 2019; 2:7
https://doi.org/10.1186/s42397-019-0023-4

Effects of NaCl stress on the biochemical substances in Bt cotton as well as on the growth and development and adult oviposition selectivity of Helicoverpa armigera

Background

Recently, due to the development of food security strategies, cotton has been planted in inland saline-alkali dry soils or in coastal some saline-alkali soils in China. Under the condition, to comprehensively prevent and control Helicoverpa armigera in cotton fields with saline-alkali soils, it is important to study the larval growth and development of H. armigera and to study adult oviposition selectivity in H. armigera adults that feed on NaCl-stressed cotton plants.

Results

In this study, Bt cotton GK19 was used for the experimental group and its nontransgenic parent Simian 3 was used for the control to study the effects of biochemical substances in cotton as well as larval growth and development and adult oviposition selectivity of H. armigera. The experiments were performed by growing cotton indoors under NaCl stress at concentrations of 0 mmol·L− 1, 75 mmol·L− 1 and 150 mmol·L− 1, respectively. The results showed that the expression of Bt protein was significantly inhibited for NaCl-stressed Bt cotton. The content of soluble protein and K+ in the leaves of cotton were decreased, while the content of gossypol and Na+ were increased. In addition, the 5th instar H. armigera larvae exhibited shorten the life span in a 13-day trial period. Under enclosure treatments and at different female densities, the adult oviposition of H. armigera decreased on high NaCl-stressed nontransgenic cotton, while the oviposition on Bt cotton tended to first increase but then decrease under low, moderate and high NaCl stress treatments.

Conclusions

Under certain content ranges of NaCl stress treatments, larval of H. armigera growth and development, and adult oviposition were no significant difference in the change for a certain period. However, under high NaCl stress, larval growth, development and adult oviposition were affected, which may provide insights for the prevention and control of H. armigera for Bt cotton in saline-alkali soils.

 

Effects of NaCl stress on the biochemical substances in Bt cotton as well as on the growth and development and adult oviposition selectivity of Helicoverpa armigera

LUO Junyu, ZHANG Shuai, ZHU Xiangzhen, JI Jichao, ZHANG Kaixin, WANG Chunyi, ZHANG Lijuan, WANG Li and CUI Jiniie

Journal of Cotton Research. 2019; 2:4

https://doi.org/10.1186/s42397-019-0020-7

 

https://jcottonres.biomedcentral.com/articles/10.1186/s42397-019-0020-7

Relative Resistance of Gossypium Species to Insect Complex Under Non-Sprayed Conditions

ABSTRACT
A number of varieties and strains of Gossypium were grown under non-sprayed conditions to evaluate their relative resistance against insects during two seasons 1993-94 and 1994-95. The strains belonged to Gossypium. Barbadense (Pima), G. palmeri, G. arboreum and G. hirsutum. These varieties had varying degree of resistance to insects. The pima types were highly susceptible to sucking insects and Cotton Leaf Curl Virus. The two entries of G. palmeri exhibited complete tolerance to all sucking insects and Cotton Leaf Curl Virus. Their leaves were lush green, showing no sign of sucking insects injury. The source of resistance in G. palmeri is not known. If this character could be successfully transferred to upland cotton, it may revolutionize cotton production. The potential for substantial saving on insecticides could also lead to reduced environmental pollution. Varieties of G. hirsutum and G. arboreum had a varying but higher degree of resistance against sucking insects, compared to pima types

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Imidcloprid Seed Treatment Effect on Sucking Pests, Predators, Plant Growth and Productivity in Cotton

ABSTRACT
Imidacloprid seed treatment reduced the jassid populations by 65% in research station studies without affecting predator coccinellids. In farmer participatory trials aimed at area-wide management” of cotton pests during the past two seasons, it reduced jassids by 62-79% and aphids by 66-72% without affecting the predator coccinellids. It also substantially increased plant height (23-30%) up to eight weeks from planting and increased square production (32-49%) during the initial fruiting period. Further, it helped to eliminate foliar sprays against sucking pests in 19 out of 20 farms for 40-50 days. Fields that did not receive seed treatment, required 1-3 foliar sprays to keep the sucking pests under check. This seed treatment, combined with other management tactics employed for area-wide management of cotton pests, resulted in an increase in seed cotton yields by 28-31% over farmer managed fields without seed treatment.

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Chemical Seed Treatments for the Control of Cotton Seedling Pathogens

ABSTRACT
Seedling diseases of cotton are a very serious problem in Greece because planting starts early in the spring when cold soil and weather conditions favour the development of the disease. The major soil dorne pathogens involved are Pythium ultimatum, Rhizoctonia solani and Thielaviopsis basicola. Cotton seed treatments are designed to protect seed and seedlings from the pathogen complex that cause the seeds, roots and hypocotiyl to rot. Following many years of testing, Vitavex was found to be the most effective against R. solani while two different commercial formulations of metalaxyl (Apron and Ridomil) were found to be effective against P. ultimatum. Black root rot of cotton was significantly reduced when cotton seed was treated with any one of the fungicides Benlate, Bayfidan or Bayleton. Combinations of metalaxyl, benlate and carboxin were found to be effective against damping off caused by all three pathogens. Evaluation of cotton seed treatments in 1994 showed that metalaxyl plus carboxin was the combination that gave the highest final cotton seedling survival. However, the specific pathogen controlled in this trial was R. solani.

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New Developments in Cottonseed Treatment from China, CIS Republics and United StatesNew Developments in Cottonseed Treatment from China, CIS Republics and United States

ABSTRACT
Research results from the three largest cotton producing areas of the world have demonstrated significant increases in disease control and cotton yields by utilizing new combination chemical seed treatments. In China, 16 formulations were studied at eight field trial sites in four provinces for several years. Combinations of 2-(thiocyanomethylthio) benzothiazole, a-butyl-a-(4-chlorophenyl)-1 H-1,2,4-triazole-1-propanenitrile and N-(2,6-dimethylphenyl)-N-(methoxyacetyl) alanine methyl ester significantly increased plant stand and yield compared to single and composite treatments. This combination has also demonstrated significant increases in cotton stand and survival in field trials conducted across the cotton growing area of the United States, over 4 years. In Uzbekistan, the combination of 2-(thiocyanomethylthio) benzothiazole, 1,4-dichloro-2,5-dimethyoxybenzene and O,S-dimethyl acetylphosphoramidothioate significantly increased disease control and yield compared to the standard treatment, Bromotak and Thiram. The incidence of bacterial blight caused by Xanthomonas campestris, was also significantly reduced. It is concluded from these studies that cottonseed treatments containing a broad spectrum contact fungicide in combination with systemic products with activity against Pythium, Rhizoctonia and Thielaviopsis are highly effective in establishing acceptable field populations of cotton plants.

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An EAn Evaluation of Insecticide Seed Treatments Against Thrips in Southern Australiavaluation of Insecticide Seed Treatments Against Thrips in Southern Australia

ABSTRACT
Thrips (Thrips tabaci and Frankliniella schultzei) are common seedling pests of Australian cotton crops. They are controlled using insecticide seed treatments, soil applied insecticide granules or foliar insecticides. To assess the relative value of these control options, their efficacy was assessed in the field. The yield response of cotton was also assessed to indicate the effect of thrips damage on yield. Cotton protected with thiodicarb, imidacloprid, or a combination of thiodicarb and fipronil, applied as seed treatments was compared with that protected by in-furrow applied aldicarb granules and with untreated seed. Replicated experiments were carried out on commercial cotton farms at 14 sites throughout Australia over 2 seasons. Experiments were unsprayed through the early season, when thrips were present, but after that, insect pests were managed according to best commercial practice. Varieties expressing the Cry 1Ac protein were used to minimize potential confounding effects due to damage by Helicoverpa spp. Aldicarb provided the best control of thrips, followed by imidacloprid, fipronil and thiodicarb. Yield increases were recorded at only 4 of the 13 sites harvested. The magnitude of the yield increase from thrip control appeared to be related to the seasonal abundance of thrips, the growing conditions and treatment efficacy.

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Cottonseed Treatment in Addition to Chemical Control of Sporadic Pests for the Small Scale Farmer

ABSTRACT
Cottonseed treatment trials over two to three seasons showed that phorate and terbufos have potential as seed dressings to protect young cotton plants against pests. Bio-assays indicated that germinating cotton plants are capable of absorbing and transporting sufficient insecticide to produce satisfactory mortality in pests such as Syagrus rugifrons Baly the black cotton beetle, and other ground insects, e.g. crickets, that damage cotton seedlings. The black cotton beetle is a pest on cotton seedlings and ratoon cotton on the Springbok Flats in the Northern Province. Soil treatment and seed treatment with terbufos effectively prevented root damage early in the season, while follow-up applications of monocrotophos or abamectin in combination with endosulfan (Thioflo), controlled plant damage above the soil. Endosulfan in combination with profenofos and carbaryl resulted in significant yield increases. Monocrotophos simultaneously controls the American bollworm (Helicoverpa armigera Hübner), the main pest of cotton. Monocrotophos also shows potential to control the cotton stem weevil, Apion soleatum Wagner (Apionidae: Coleoptera), a relatively new pest in the lowveld areas of KwaZulu-Natal and Mpumalanga, where many small-scale farmers produce cotton. An integrated pest management programme that includes seed treatment and limited use of insecticides that control a number of pest species at the same time, is suggested for small-scale farmers.

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Chemical Control of Aphid Populations in Cotton Using Hydraulic and Electrostatic Sprayers and Aphid Alarm Pheromone

ABSTRACT
In experimental cotton fields in Lianoverghi, Imathia, Greece in 1995 (cultivar Zeta-2) and Velestino, Magnesia in 1996 (cultivar Corina), experiments comparisons were made between different application methods for chemical control of aphids. There were five treatments in a randomized complete block design in four replications. The treatments were: control, cyhalothrin sprayed with hydraulic or electrostatic sprayer and cyhalothrin with pheromone sprayed with hydraulic or electrostatic sprayer. Observations of the presence of aphids were taken 1-2 days before and 7-8 and 20 days after the applications. The predominant aphid species in both regions was Aphis gossypii Glover. The electrostatic sprayer was more effective than the hydraulic. The presence of the pheromone did not change the efficiency of the insecticide with either method. Both methods were less effective when aphid populations were high. Aphid populations were high in untreated plots 7 days after spraying, but later declined below populations in the treated plots, possibly because of the activity of natural enemies. The electrostatic sprayer was less efficient than the hydraulic when aphid populations were very high and full grown plants formed a continuous canopy.

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