Survey and collection of Cercospora leaf spot samples

Fifty-five Cercospora leaf spot samples have been collected from nine major cotton growing districts of Karnataka, namely Dharwad, Haveri, Gadag, Belagavi, Raichur, Vijayapura, Yadagiri, Kalaburagi and Ballari. PDI ranged from 2.5 to 12.0 in the survey. Ten samples were collected from the Kurnool district of Andhra Pradesh, and the PDI ranged from 2.5 to 7.0. Fifteen samples were collected from Ranga Reddy, Warangal, Nirmal, and Adilabad districts of Telangana, and the PDI ranged from 4.0 to 7.0. Twenty samples were collected from the Coimbatore, Annur, and Kinathukadavu blocks of Coimbatore district, Tamil Nadu, and PDI values ranging from 2.0 to 8.5 were recorded.

Morphological identification of Cercospora isolates

Colony colour ranged from dull to dark grey, ashy, or greyish black, with an irregular or smooth colony margin on PDA. Mycelium is flat to medium-raised, with a velvety to smooth texture. Conidiophores were short, unbranched, tufted, olivaceous, pale brown and septate. They were fasciculate and pale towards the apex. They were straight or slightly curved. Conidia were thin-walled, hyaline, and multi-septate. They were needle-shaped, slender and slightly curved.  Tips of the conidia were straight or variously curved. Acicular with an acute base with thickened and darkened hila at the base. Conidia 55-165 x 3 – 5 µm in size with 7 – 19 septa.

Pathogenicity and virulence characterization of Cercospora isolates

PDI ranged from 11.0 to 34.0 for 29 Karnataka isolates on LRA 5166. Among them, 3 isolates were recorded as highly virulent, 13 as moderately virulent and 13 as less virulent. PDIs of 7 Telangana isolates ranged from 14.0 to 23.5; 3 were classified as moderately virulent and 4 as less virulent. PDI ranged from 12.0 to 21.5 for 6 Andhra Pradesh isolates. Among them, 2 isolates were recorded as moderately virulent and 4 as less virulent. Tamil Nadu isolates showed PDI values ranging from 15.0 to 26.0 for 9 isolates. Five isolates were moderately virulent, and 4 were less virulent.

Identification of Alternaria isolates using housekeeping gene primers

Alternaria specific housekeeping gene primer Alt a1 amplified 497 bp, GAPDH primers amplified 550 bp, TEF-1 α gene primers (EF1-728F and EF1-986R) amplified 300 bp, β-tubulin primers (β-tub1 and β-tub2) amplified 300 bp, and Bt1a and Bt1b amplified 1419 bp and RPB2 primers (5F2 and 7cR) amplified 1000 bp for all 15 isolates 

TEF1 and TEF2 amplified 835 bp for 9 isolates and 900 bp for 5 isolates.  Plasma membrane ATPase primers amplified a 1201-bp fragment in 8 of 15 isolates. Calmodulin gene primers amplified a 566-bp fragment in 13 isolates and an 800-bp fragment in one isolate. DF and DR amplified 940 bp for 9 isolates and 1100 bp for 2 isolates. Most isolates were identified as A. macrospora at the species level, followed by a few isolates of A. alternata.

 Survey on Tobacco Streak Virus Incidence

A survey on TSV in Kurnool (10 mandals, 17 villages), Nandyal (2 mandals, 7 villages), and Anantapur (1 mandal, 2 villages) districts of Andhra Pradesh was conducted during the 2023-24 crop season. Kurnool recorded a 4.0 – 42.0% disease incidence (average 10.26%). Three fields recorded >20% incidence, and three fields were disease-free. Nandyal recorded 4.0 – 12.0% incidence (average 7.14%). Anantapur recorded an incidence of 0.0-3.0%. A lower thrips population was observed in the visited fields. Cotton fields were also visited in Adilabad (0.5 -1.0%), Nirmal (0.5 -1.0%), Warangal (3.0 to 19.0%), Siddipet (5.0 to 12.0%), Ranga Reddy (9.0 to 14.0%) and Medak (5.0 to 12.0%) districts of Telangana. Coimbatore district recorded 0.5 to 40.0% incidence (average 11.0%). The RCH659 BGII hybrid recorded the highest incidence of 40.0% across all symptom types.

Three surveys on TSV in Kurnool (11 mandals, 63 locations), Nandyal (1 mandal, 7 locations), and Anantapur (1 mandal, 8 locations) districts of Andhra Pradesh, and in Ballari district (1 mandal, 1 village) of Karnataka, were conducted during the 2024-25 crop season. TSV was not recorded in most fields, except for three. One field in Ballari district recorded 5.0% TSV incidence. TSV (5.0 -7.0%) was recorded in late sown (72 to 75 DAS) Jadoo BG II in Gadivemula of Nandyal district and traces in Midtur of Kurnool district. Thrips were also collected and identified as Thrips palmi. TSV was not recorded among the 10 fields in the Khammam district of Telangana. Coimbatore district recorded TSV ranging from 0.5% to 5.0%. Sixty-five cotton cultivars were screened for TSV under field conditions at CICR Coimbatore and RARS, Nandyal. TSV symptoms observed among 23 cultivars (0.56 -12.0 PDI). Nine cultivars were found to be tolerant, and 14 were susceptible to sucking pests in Coimbatore.

BOOKS EDITED

• M V Venugopalan and YG Prasad- Tamil Translation: S. Usha Rani, K. Sankaranarayanan, A. Sampathkumar, M. Sabesh, A.H. Prakash, T.N. Sujeetha, M. Sathishkumar, G. Suresh, R. Karthika, K. Suganya and K. Arun Balaji, 2024. HDPS Cotton Cultivation – Questions and Answers (Tamil) by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 50p.
• S. Usha Rani, A. Sampathkumar, M. Sabesh, A.H. Prakash, T.N. Sujeetha, M. Sathishkumar, G. Suresh (Eds.) 2024. Vaazhvai Viruthiyakkum Paruthi – Technical Guide to Cotton stakeholders (Tamil book) by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore.

RESEARCH ARTICLES (not more than 10)

• A.Sampathkumar, K. Eraivan Arutkani Aiyanathan, S. Nakkeeran and S. Manickam (2023) Multifaceted Bacillus spp. for the management of cotton bacterial blight caused by Xanthomonas citri pv. malvacearum. Biological Control. 177. https://doi.org/10.1016/j.biocontrol.2022.105111.

• A.Sampathkumar, Venkatesh R. Kulkarni, J. M. Nidagundi and A. H. Prakash (2023) Occurrence and Present Situation of Cercospora Leaf Spot Disease of Cotton in South Zone of India. Biological Forum – An International Journal 15 (4): 301-306
• A.Sampathkumar and K. P. Raghavendra (2023) Molecular identification and genetic diversity of Alternaria isolates causing leaf spot disease in cotton from major cotton growing areas of South Zone of India. Indian Journal of Agricultural Research. doi10.18805/IJARe.A-6104.
• A.Sampathkumar, Venkatesh R. Kulkarni, J. M. Nidagundi and A. H. Prakash (2023) Present Status and Prevalence of Alternaria leaf spot disease of cotton in India. Journal of Cotton Research and Development 37 (1): 83-90 
• A.Sampathkumar and A. H. Prakash (2023) Cultural, morphological variability and pathogenic diversity of Alternaria isolates of cotton from major cotton growing areas of India. The Pharma Innovation Journal 12 (2): 3321-3329

TECHNICAL FOLDERS

• A.Sampathkumar, K Rameash, R Pramoth Kumar, AH Prakash. (2022). Boll rot in cotton:  symptom and integrated management practices by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 4p.
• அ. சம்பத்குமார்,  கு. ரமேஷ், ர. பிரமோத் குமார், ஏ. ஹெச். பிரகாஷ். 2022. பருத்தியில் காய் அழுகல் நோய்: அறிகுறிகள் மற்றும் ஒருங்கிணைந்த மேலாண்மை முறைகள் (Tamil Folder) ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 4p.
• A.Sampathkumar, K. Shankarganesh, K. Ramesh, R. Raja, S. Manickam, A. H. Prakash and Y. G. Prasad, 2023. Cotton diseases and their integrated management practices by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 4p.
• R. Raja, K. Shankarganesh, K. Ramesh, A. Sampathkumar, S. Manickam, A. H. Prakash and Y. G. Prasad, 2023. Fertilizer management in ELS cotton production by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 4p.

BOOK CHAPTERS AND CONFERENCE PROCEEDINGS

• A.Sampathkumar, P. Valarmathi, S. Usha Rani, T.N. Sujeetha, M. Sathishkumar and G. Suresh (2024). Cotton diseases and integrated management practices in the book (Eds.) S. Usha Rani, A. Sampathkumar, M. Sabesh, A.H. Prakash, T.N. Sujeetha, M. Sathishkumar, G. Suresh. Vaazhvai Viruthiyakkum Paruthi – Technical Guide to Cotton stakeholders (Tamil book) by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, PP. 125-140.

International

• Oral presentation on “Species identification and genetic variability of Alternaria isolates causing leaf spot disease in cotton collected from South Zone of India” in the International Conference on “Innovative Technologies for Research and Development for Sustainable Production of Cotton, Oilseeds and Fibre Crops” held at ELA, OLD GOA from 13-15 November, 2024
• Oral presentation on “Current Status of Tobacco Streak Virus of Cotton in South Zone of India” in the International Conference on “Unleashing the Power of Seed & Crop Health Innovations for food secure World” held from 21-22 Nov, 2024 at Tamil Nadu Agricultural University, Coimbatore jointly organized by TNAU, Coimbatore and Shastri Indo-Canadian Institute, New Delhi

National

• Oral presentation on “Current status of Cercospora leaf spot disease of cotton and morphological and virulence diversity of pathogen” in the National Seminar on “Sustainable Livelihoods in Agri-food Systems: Enhancing Rural Prosperity” held at College of Agriculture, Pasighat, Arunachal Pradesh from 11-12 March, 2025 Organized by College of Agriculture, CAU(I), Pasighat, Arunachal Pradesh in association with ICAR-Central Institute for Cotton Research, Nagpur, Maharashtra
• Oral presentation on “Outbreak of Tobacco Streak Virus in Cotton and factors influencing its spread and severity in South Zone” in the National conference on “Transforming Plant Health Management: Integrating Traditional Practices with Modern Innovations for Global Food Security” held at Pandit Jawaharlal Nehru College of Agriculture and Research Institute (PAJANCOA & RI), Karaikal, UT of Puducherry from 18-19 December, 2025 Organized by Indian Phytopathological Society (Southern Zone Chapter) and PAJANCOA & RI, Karaikal, UT of Puducherry
• Oral presentation on “Screening of parental genotypes of Bt G. hirsutum, G. barbadense and HxB hybrids of cotton for disease tolerance under field conditions” in the National Seminar on “Sustainable Agri-Horti Systems: Bridging the Gap between Tradition & Innovation” held at College of Agriculture, CAU (I), Pasighat, Arunachal Pradesh from 11-12 February, 2026 Organized by College of Agriculture, CAU (I), Pasighat, Arunachal Pradesh in collaboration with ICAR- Indian Institute of Rice Research, Hyderabad and ICAR- Central Institute for Cotton Research, Nagpur

POPULAR ARTICLES/ SHORT NOTES/ SHORT COMMUNICATIONS 

• Sampathkumar 2021 Cotton bacterial blight pathogen Xanthomonas citri pv. malvacearum: Overview on its virulence, races and genetic diversity. Cotton Innovate, Vol. 9 (1), pp 1-3.

RESEARCH BULLETIN/ EXTENSION BULLETINS 

• A. Sampathkumar, S. Usha Rani, M. Sabesh, A.H. Prakash, Y.G. Prasad, T.N. Sujeetha, M. Sathishkumar and G. Suresh, 2024. Cotton Diseases: Symptoms identification and integrated management practices, Technical Bulletin by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 31p.
• A. Sampathkumar, S. Usha Rani, M. Sabesh, A.H. Prakash, Y.G. Prasad, T.N. Sujeetha, M. Sathishkumar and G. Suresh, 2024. Cotton Diseases: Symptoms identification and integrated management practices (Tamil), Technical Bulletin by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 27p.
• K. Shankarganesh, K. Ramesh, A. Sampathkumar, R. Raja, S. Manickam, A. H. Prakash and Y. G. Prasad, 2023. Cotton insect pests and their management by ICAR – Central Institute for Cotton Research, Regional Station, Coimbatore, 24p.