Response of successive three generations of cotton,bollworm,Helicoverpa armigera (Hübner),fed on cotton bolls under elevated CO_2

The growth, development and consumption of successive three generations of cotton bollworm, Helicoverpa armigera （Htibner）, fed on cotton bolls grown under elevated CO2 （double-ambient vs. ambient） in open-top chambers were examined. Significant decreases in protein, total amino acid, water and nitrogen content and increases in free fatty acid were observed in cotton bolls. Changes in quality of cotton bolls affected the growth, development and food utilization of H. armigera. Significantly longer larval development duration in three successive generations and lower pupal weight of the second and third generations were observed in cotton bollworm fed on cotton bolls grown under elevated CO2. Significantly lower fecundity was also found in successive three generations of H. armigera fed on cotton bolls grown under elevated CO2. The consumption per larva occurred significant increase in successive three generations and frass per larva were also significantly increased during the second and third generations under elevated CO2. Significantly lower relative growth rate, efficiency of conversion of ingested food and significant higher relative consumption rate in successive three generations were observed in cotton bollworm fed on cotton bolls grown under elevated CO2. Significantly lower potential female fecundity, larval numbers and population consumption were found in the second and third generations of cotton bollworm fed on cotton bolls grown under elevated CO2. The integrative effect of higher larval mortality rate and lower adult fecundity resulted in significant decreases in potential population consumption in the latter two generations. The results show that elevated CO2 adversely affects cotton bolls quality, which indicates the potential population dynamics and potential population consumption of cotton bollworm will alleviate the harm to the plants in the future rising CO2 atmosphere.

A Serratia marcesens Strains Involved in Cotton (<i>Gossypium hirsutum</i>) Boll Infection by a Prokaryote

A boll infection caused by non-traditional cotton pathogens was first reported to occur in the southeastern U.S. Cotton Belt (year 2000) and has since spread to Texas causing significant yield losses. This study was aimed towards investigating the verde plant bug (Creontiades signatus) link between interior boll disease in Texas, USA. Using glasshouse grown bolls, bacteria recovered from locules with disease symptoms from field-grown cotton bolls caged with the piercing-sucking C. signatus were analyzed for the capacity to inflict the disease. For pathogenicity testing, spontaneously generated rifampicin resistant (Rifr) variants were utilized to track the antibiotic resistant bacterium and deter growth of endophytic and contaminating bacteria. To simulate C. signatus feeding, a needle (31 gauge) was employed to inoculate bolls at 13 - 15 days after flower bloom. Bacterial suspensions ranged from 101 - 106 colony forming units/ml. Field infection symptoms were duplicated after two weeks of bacterial exposure. Infectious strains were best categorized as Serratia marcescens based on traditional carbon utilization and enzyme production testing, and a 99% nucleotide sequence identity of 16S ribosomal DNA. Putative S. marcescens representatives isolated from rotted bolls exposed to C. signatus were shown to reproduce field infection symptoms upon inoculation into greenhouse grown fruit. Serratia spp. can inflict disease in alfalfa, cucurbits, and sunflower. The presented data are the first to definitively show that a Serratia sp. has the capacity to infect cotton.

Climatic variables: Evaporation, sunshine, relative humidity, soil and air temperature and its adverse effects on cotton production

Cotton yield is a function of growth rates,flower production rates,and flower and boll retention during the fruiting period.Information on the relationship between climatic factors and the cotton plant’s ability to produce and sustain flower buds,flowers,and bolls will allow one to model plant responses to conditions that frequently occur in the field and to predict developmental rate or the formation of these organs.This study investigates the statistical relationship between various climatic factors and overall flower and boll production.Also,the relationship between climatic factors and production of flowers and bolls obtained during the development periods of the flowering and boll stage.Further,predicting effects of climatic factors during different convenient intervals(in days)on cotton flower and boll production compared with daily observations.Evaporation,sunshine duration,relative humidity,surface soil temperature at 1800 h,and maximum air temperature,are the important climatic factors that significantly affect flower and boll production.The five-day interval was found to be more adequately and sensibly related to yield parameters.Evaporation;minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention.There was a negative correlation between flower and boll production and either evaporation or sunshine duration,while that correlation with minimum relative humidity was positive.