FUNGAL DISEASES
First Report of Corynespora Leaf Spot of Cotton Caused by Corynespora cassiicola in Central India
Corynespora Leaf Spot of Cotton caused by Corynespora cassiicola in Central India was reported for the first time. The fungus was reisolated from inoculated leaves and confirmed as C. cassiicola. The internal transcribed spacer region of rDNA was amplified with ITS-1/ITS-4 universal primers and sequenced. Resulting sequences submitted to GenBank (MG976657, MG976661, and MG976664) showed 100% identity with C. cassiicola from avocado (KU593529). Because the disease has the potential to be severe, it could become a significant concern for cotton growers in central India.
Further readings: https://apsjournals.apsnet.org/doi/10.1094/PDIS-05-18-0823-PDN
RUST DISEASE OF COTTON
The presence of rust disease in the cotton genotypes were observed at Coimbatore. The common symptoms are the appearance of brown pustules on the lower surface of leaves. These pustules are surrounded with a purple halo. Symptoms also appear in petioles, stem and boll. There was a decrease in photosynthetic area of leaves due to rust pustules and finally severe defoliation was noticed in the field which resulted in the reduction of cotton yield. Uredeospores of Phakopsora gossypii are thin-walled, single celled, oval in shape and rusty red or pale brown in colour . Teliospores was not observed in the infected leaves of cotton. The disease incidence ranges from 5.31 % to 52.12 % in various Bt hybrids and varieties.
BACTERIAL DISEASES
Association of phytopathogenic Pantoea dispersa inner boll rot of cotton (Gossypium hirsutum L.) in Maharashtra state, India
Green bolls with and without any sign of damage were collected from farmers fields and dissected under aseptic conditions. Bacterial species belonging to members of Enterobacteriaceae family (facultative anaerobe) were predominately isolated from rot affected cotton bolls. Four bacterial strains isolated from four locations were identified on the basis of morphological, biochemical and molecular characterization. Pathogenicity of all the four isolates (CBR2-YTML, CBR1-JLGN, CBR2-BLDN and CBR5-JLGN) was proved by Koch’s postulates. Tthis is the first report of occurrence and association of phytopathogenic bacteria Pantoea dispersa, a member of the Enterobacteriaceae family as a potential and principal pathogenic agent causing inner cotton (G. hirsutum L.) boll rots in Maharashtra state, India.
Further readings: https://link.springer.com/article/10.1007/s10658-020-02071-0
VIRUS DISEASES
Development of loop mediated isothermal amplification (LAMP): A new tool for rapid diagnosis of cotton leaf curl viral disease
Cotton leaf curl disease (CLCuD) ranks top among all endemic diseases transmitted by whitefly (Bemisia tabaci) affecting cotton (Gossypium hirsutum) causing severe economic losses to the cotton growers in the Indian subcontinent. For its effective management, robust tools for detection are a prerequisite and it is important to diagnose the virus titre in early stage of infection in plants as well as in the disease transmitting vector. Considering the limitations in current PCR-based techniques we have standardised rapid and sensitive Loop Mediated Isothermal Amplification (LAMP) protocol for the diagnosis of cotton leaf curl virus (CLCuV) in cotton leaves and in its transmitting vector whitefly. Perhaps, this is the first report of use of LAMP tool for rapid diagnosis of CLCuV in cotton and its transmitting vector the whitefly.
Further readings: https://pubmed.ncbi.nlm.nih.gov/35568082/
Tobacco streak virus (TSV) disease
TSV was recorded in all the species of cotton. The symptom expression in Gossypium barbadense was very distinct with dark purple necrotic spots and drying of squares. Typical symptoms observed in G. hirsutum were chlorotic with necrotic spots in young leaves and marginal necrotic streaks with leaf deformation. Whereas in matured plants veinal necrosis, drying of squares and also in terminal shoots was observed. Yellowing, leaf malformation and necrotic spots were observed in G. arboreum.
Further readings: http://www.crdaindia.com/fileserve.php?FID=692 https://www.cabdirect.org/cabdirect/abstract/20203190141
Genetic Similarity between Cotton Leafroll Dwarf Virus and Chickpea Stunt Disease Associated Virus in India
The cotton leafroll dwarf virus (CLRDV) is one of the most devastating pathogens of cotton. This malady, known as cotton blue disease, is widespread in South America where it causes huge crop losses. Recently the disease has been reported from India. We noticed occurrence of cotton blue disease and chickpea stunt disease in adjoining cotton and chickpea fields and got interested in knowing if these two viral diseases have some association. Our studies indicate that CpSDaV and CLRDV in India are possibly two different strains of the same virus.
Further readings: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5117868/
DISEASE MANAGEMENT
Antagonistic potential and phylogeny of culturable endophytic fungi isolated from desi cotton (Gossypium arboreum L.)
Twenty three fungal endophytes were isolated and identified from Gossypium arboreum. These endophytes were evaluated against two pathogens Corynespora cassiicola and Fusarium solani wherein Nigrospora sphaerica was found efficient. Four antimicrobial VOCs were identified from N. sphaerica through GC/MS analysis. Phylogeny tree revealed that the isolates were grouped into 4 classes and six orders, of which Dothidiomycetes was the most prevalent class.
Further readings: https://www.sciencedirect.com/science/article/pii/S0254629919325189
Most virulent and insecticide compatible entomopathogens
Among 370 entomopathognes the top ten entomopathogenic strains including Beauveria bassiana, Metarhizium anisoplii, and Fusarium verticillioides resulted in 75-95% nymphal mortality and found to be the most compatible with full and/ or half doses of the chemicals (9) and botanicals (3).
Further readings: https://10.1186/s41938-019-0130-z, https://10.1016/j.jip.2021.107618
New modified poly house bioassay method (NMPBM):
Developed new modified poly house bioassay method (NMPBM offering a simple, low cost, less time and labour-intensive alternatives for identifying most virulent microbial and developing microbial-based solutions for biocontrol. Insect rearing cages, aspirator, scissors are not required for egg laying, conducting bioassay in net/polyhouse. No extra care required for minimizing contamination as it happens in laboratory bioassay tests.
Further readings: https://10.1007/s13744-022-00964-9, https://10.1584/jpestics.D18-067
Factors responsible for parawilt/sudden wilt in the North Cotton growing zone
The major factor responsible for parawilt in North Zone, were identified as no deep ploughing, cotton-wheat-cotton cropping system, or early irrigation (before 30 DAS), more than the past 5 years, high soil EC (2.5 to 4.5 dS/m) and pH (7.6 to 7.9). These practices and soil conditions are responsible for increased vulnerability of cotton sudden wilting, root rot, nematodes, fungal foliar spots, and termites/root rot.
Further readings: http://www.crdaindia.com/fileserve.php?FID=768, https://10.5281/zenodo.7536187
FUNGAL DISEASES
First Report of Corynespora Leaf Spot of Cotton Caused by Corynespora cassiicola in Central India
Corynespora Leaf Spot of Cotton caused by Corynespora cassiicola in Central India was reported for the first time. The fungus was reisolated from inoculated leaves and confirmed as C. cassiicola. The internal transcribed spacer region of rDNA was amplified with ITS-1/ITS-4 universal primers and sequenced. Resulting sequences submitted to GenBank (MG976657, MG976661, and MG976664) showed 100% identity with C. cassiicola from avocado (KU593529). Because the disease has the potential to be severe, it could become a significant concern for cotton growers in central India.
Further readings: https://apsjournals.apsnet.org/doi/10.1094/PDIS-05-18-0823-PDN
RUST DISEASE OF COTTON
The presence of rust disease in the cotton genotypes were observed at Coimbatore. The common symptoms are the appearance of brown pustules on the lower surface of leaves. These pustules are surrounded with a purple halo. Symptoms also appear in petioles, stem and boll. There was a decrease in photosynthetic area of leaves due to rust pustules and finally severe defoliation was noticed in the field which resulted in the reduction of cotton yield. Uredeospores of Phakopsora gossypii are thin-walled, single celled, oval in shape and rusty red or pale brown in colour . Teliospores was not observed in the infected leaves of cotton. The disease incidence ranges from 5.31 % to 52.12 % in various Bt hybrids and varieties.
BACTERIAL DISEASES
Association of phytopathogenic Pantoea dispersa inner boll rot of cotton (Gossypium hirsutum L.) in Maharashtra state, India
Green bolls with and without any sign of damage were collected from farmers fields and dissected under aseptic conditions. Bacterial species belonging to members of Enterobacteriaceae family (facultative anaerobe) were predominately isolated from rot affected cotton bolls. Four bacterial strains isolated from four locations were identified on the basis of morphological, biochemical and molecular characterization. Pathogenicity of all the four isolates (CBR2-YTML, CBR1-JLGN, CBR2-BLDN and CBR5-JLGN) was proved by Koch’s postulates. Tthis is the first report of occurrence and association of phytopathogenic bacteria Pantoea dispersa, a member of the Enterobacteriaceae family as a potential and principal pathogenic agent causing inner cotton (G. hirsutum L.) boll rots in Maharashtra state, India.
Further readings: https://link.springer.com/article/10.1007/s10658-020-02071-0
VIRUS DISEASES
Development of loop mediated isothermal amplification (LAMP): A new tool for rapid diagnosis of cotton leaf curl viral disease
Cotton leaf curl disease (CLCuD) ranks top among all endemic diseases transmitted by whitefly (Bemisia tabaci) affecting cotton (Gossypium hirsutum) causing severe economic losses to the cotton growers in the Indian subcontinent. For its effective management, robust tools for detection are a prerequisite and it is important to diagnose the virus titre in early stage of infection in plants as well as in the disease transmitting vector. Considering the limitations in current PCR-based techniques we have standardised rapid and sensitive Loop Mediated Isothermal Amplification (LAMP) protocol for the diagnosis of cotton leaf curl virus (CLCuV) in cotton leaves and in its transmitting vector whitefly. Perhaps, this is the first report of use of LAMP tool for rapid diagnosis of CLCuV in cotton and its transmitting vector the whitefly.
Further readings: https://pubmed.ncbi.nlm.nih.gov/35568082/
Tobacco streak virus (TSV) disease
TSV was recorded in all the species of cotton. The symptom expression in Gossypium barbadense was very distinct with dark purple necrotic spots and drying of squares. Typical symptoms observed in G. hirsutum were chlorotic with necrotic spots in young leaves and marginal necrotic streaks with leaf deformation. Whereas in matured plants veinal necrosis, drying of squares and also in terminal shoots was observed. Yellowing, leaf malformation and necrotic spots were observed in G. arboreum.
Further readings: http://www.crdaindia.com/fileserve.php?FID=692 https://www.cabdirect.org/cabdirect/abstract/20203190141
Genetic Similarity between Cotton Leafroll Dwarf Virus and Chickpea Stunt Disease Associated Virus in India
The cotton leafroll dwarf virus (CLRDV) is one of the most devastating pathogens of cotton. This malady, known as cotton blue disease, is widespread in South America where it causes huge crop losses. Recently the disease has been reported from India. We noticed occurrence of cotton blue disease and chickpea stunt disease in adjoining cotton and chickpea fields and got interested in knowing if these two viral diseases have some association. Our studies indicate that CpSDaV and CLRDV in India are possibly two different strains of the same virus.
Further readings: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5117868/
DISEASE MANAGEMENT
Antagonistic potential and phylogeny of culturable endophytic fungi isolated from desi cotton (Gossypium arboreum L.)
Twenty three fungal endophytes were isolated and identified from Gossypium arboreum. These endophytes were evaluated against two pathogens Corynespora cassiicola and Fusarium solani wherein Nigrospora sphaerica was found efficient. Four antimicrobial VOCs were identified from N. sphaerica through GC/MS analysis. Phylogeny tree revealed that the isolates were grouped into 4 classes and six orders, of which Dothidiomycetes was the most prevalent class.
Further readings: https://www.sciencedirect.com/science/article/pii/S0254629919325189
Most virulent and insecticide compatible entomopathogens
Among 370 entomopathognes the top ten entomopathogenic strains including Beauveria bassiana, Metarhizium anisoplii, and Fusarium verticillioides resulted in 75-95% nymphal mortality and found to be the most compatible with full and/ or half doses of the chemicals (9) and botanicals (3).
Further readings: https://10.1186/s41938-019-0130-z https://10.1016/j.jip.2021.107618
New modified poly house bioassay method (NMPBM):
Developed new modified poly house bioassay method NMPBM offering a simple, low cost, less time and labour-intensive alternatives for identifying most virulent microbial and developing microbial-based solutions for biocontrol. Insect rearing cages, aspirator, scissors are not required for egg laying, conducting bioassay in net/polyhouse. No extra care required for minimizing contamination as it happens in laboratory bioassay tests.
Further readings: https://10.1007/s13744-022-00964-9 https://10.1584/jpestics.D18-067
Factors responsible for parawilt/sudden wilt in the North Cotton growing zone
The major factor responsible for parawilt in North Zone, were identified as no deep ploughing, cotton-wheat-cotton cropping system, or early irrigation (before 30 DAS), more than the past 5 years, high soil EC (2.5 to 4.5 dS/m) and pH (7.6 to 7.9). These practices and soil conditions are responsible for increased vulnerability of cotton sudden wilting, root rot, nematodes, fungal foliar spots, and termites/root rot.
Further readings: http://www.crdaindia.com/fileserve.php?FID=768 https://10.5281/zenodo.7536187