Ramularia leaf spot and Boll rot are affected differently by organic and inorganic nitrogen fertilization in cotton plants

Background: In this work, the interaction among nitrogen fertilization using bovine manure, poultry manure, Jatropha curcas seed cake and urea, and the diseases Ramularia leaf spot (RLS) and Boll rot (BR), caused by Ramulariopsis pseudoglycines and Diplodia gossypina, respectively, on cotton plants (Gossypium hirsutum L.), was studied under field conditions. The intensity (incidence and severity in percentage) of RLS and the incidence (%) of BR were evaluated six times, starting in the reproductive stage B1 (first visible flower bud). A randomized complete block experimental design with a 4x4 factorial arrangement (fertilizers x dose), totaling 16 treatments were used. The disease progress was analyzed with the nonlinear Logistic and Gomperts models, obtaining the initial disease's epidemiological parameters (Y0) and progress rate (r). Results: Cotton plants fertilized with 100 kg N ha-1 of J. curcas seed cake and poultry manure with 100 and 200 kg N ha-1 showed an incidence between 16 and 21% of RLS. In contrast, plants fertilized with bovine manure presented the highest incidence of ramularia leaf spot (33%). Regarding factor B (dose), cotton plants fertilized with 50 kg N ha-1, showed a higher percentage of BR incidence, being different from those fertilized with the other doses. In the analysis of the interaction corresponding to the BR incidence, no response pattern was found in the doses for each fertilizer. No correlation was observed between the three health variables analyzed, finding probabilities between 0.002 and 0.892. In the temporal progress of RLS incidence, it was shown that fertilization with J. curcas seedcake and poultry manure was lower than the rest. In severity, the plants were fertilized by J. curcas seedcake concerning the rest. The progression curve of RLS severity temporarily increased similarly, observing that plants fertilized with higher doses reached a lower final proportion of the disease.Regarding the modeling of epidemics using the nonlinear Logistic and Gompertz models, the first model better represented the RLS, except for factor B, where none of the curves was significant. In the Logistic model, a lower amount of initial disease was found (Y0) of RLS, both in incidence (0.259) as in severity (0.081), in plants fertilized with J. curcas seed cake and poultry manure, compared to the rest. For the case of BR incidence, none of the nonlinear models used could be represented.Conclusions: Plants fertilized with 50 kg N ha-1, presented an incidence twice higher than those obtained with other fertilizers. The Logistic model better fits RLS, but no model was adapted to BR. Only the RLS epidemiological parameters were affected differently in this experiment compared to BR disease.

Impact of Chemical Defoliants on Chlorophyll Fluorescence, Biochemical Parameters, Yield and Fiber Quality of High Density Cotton

Background: The Cotton growing farmers in India are facing major problem at the time of harvest due to labor shortages, asynchronized boll opening, leaf trash in the cotton, which is reducing the boll picking efficiency and fiber quality. Presently, the Indian cotton industry is moving towards mechanical harvesting by cotton harvester. Defoliation or leaf abscission is induced in cotton as a natural physiological process which usually is inadequate for a complete mechanical harvest of cotton. Defoliation before harvest is often induced by managing the plants so that senescence, abscission (separation) layer development and leaf drop are encouraged. Chemical defoliants induce leaf abscission, hasten mature boll dehiscence and inhibit re­ growth. Selection of appropriate defoliants is one of the critical decisions in cotton production. Their use can result in increased manual as well as machine harvest efficiency, reducing boll rot and the trash in seed cotton. The physiological basis of defoliation in cotton is essential to understand the role of appropriate defoliant with time of application. Hence, the objective of the study was to evaluate the defoliation efficiency, boll opening percentage and to know the physiological basis of defoliation in response to different defoliants and time of application in high density Cotton cultivation which eases the mechanical harvesting.Methods: In this field investigation during 2018 - 2019 at Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore was carried with seven different defoliants and three different time of defoliants application were fixed based on crop maturity and duration of the crop. In this study, high density cotton variety CO 17 was used as experimental material. A series of lab and field analysis were determined on defoliation process, physiological attributes, boll opening percentage and seed yield and quality. The collected data were subjected to statistical analysis.Result: Our investigation exploring the effect of different defoliants on physiological, biochemical, yield and quality parameters of high density Cotton. Among the different defoliants and time of applications, two defoliants and two times of applications works better in terms of better defoliation, boll opening rate, physiology, yield and quality. The physiological and biochemical effects of defoliants on defoliation process were discussed. The present work will be useful for mechanized picking with these effective defoliants without loss of yield and quality loss in cotton.

Complete Genome Sequence of Serratia sp. Strain CC119, Associated with Inner Cotton Boll Rot via Insect Vector Transmission

Serratia species are Gram-negative bacteria that can infect both animals and plants. The annotated genome presented is the first for a Serratia sp. strain (called CC119) that is a cotton boll pathogen. The opportunistic strain is associated with the boll-piercing-sucking insect Creontiades signatus.

Transmission of Cotton Seed and Boll Rotting Bacteria by the Verde Plant Bug (Hemiptera: Miridae)

Field experiments and supporting laboratory work were conducted to characterize the ability of the verde plant bug, Creontiades signatus (Distant), a boll-feeding sucking bug, to transmit a cotton seed and boll rot bacterial pathogen, Serratia marcescens (Bizio) (Enterobacteriales: Enterobacteriaceae). Serratia marcescens was originally isolated from bolls infested with verde plant bug in south Texas, and a Rifampicin resistant S. marcescens strain was used in transmission and retention experiments. Serratia-exposed and nonexposed adult verde plant bugs from a laboratory colony were placed individually on 5-, 6-, 7-, and 8-d-old bolls (postanthesis). The bacterial acquisition process did not apparently affect insect vigor based on similar average boll injury ratings observed across both exposed and nonexposed bugs. Cotton bolls caged with Serratia-exposed verde plant bugs had significantly greater presence of S. marcescens and cotton boll rot symptoms than bolls caged without bugs (no-insect controls) or nonexposed bugs. Transmission of the disease agent by verde plant bug was confirmed across all boll ages assayed. Incidence of diseased locules on 5- and 6-d-old bolls was the same or greater than on 7- and 8-d-old bolls. Verde plant bug was able to harbor the disease agent from 24- to 96-h postinfection, and transmission efficiency rates ranged from 54 to 62% during initial transmission and retention (transmission across two bolls fed upon consecutively) studies. Along with photographic evidence, the experimental data supported that boll damage associated with verde plant bug infestations was magnified when insects transmitted the cotton pathogen S. marcescens as demonstrated in this 2-yr field experiment.