Screening of safflower genotypes against the Alternaria leaf blight of safflower

Introduction

Safflower (Carthamus tinctorius L.) is an important oilseed crop belonging to Asteraceae family, thrives in semi arid regions across the globe. It is prized for its highly nutritious edible oil from seeds that contain 25-32 per cent oil and are particularly rich in polyunsaturated fatty acids, especially linoleic acid, which comprises 78 per cent of the oil. It is native to parts of Asia, the Middle East and Africa. Safflower is cultivated in over 60 countries worldwide ranging between latitudes 50°N and 23°S (Gilbert et al., 2008) [5] . Mexico is the largest producer, followed by India. In India, the primary safflower producing states are Maharashtra and Karnataka, which together account for (86%) of the country's total production with Maharashtra contributing (55%) and Karnataka 31 per cent. Globally, safflower is cultivated on 6.94 lakh hectares, producing 6.27 lakh tonnes annually, with an average yield of 903 kg per hectare (Anon., 2020). In India, safflower is grown on 0.79 lakh hectares, yielding 0.61 lakh tonnes annually, with an average yield of 777 kg per hectare. The crop is predominantly cultivated in the Indian states of Maharashtra, Karnataka, Andhra Pradesh, Telangana, and Madhya Pradesh. Karnataka alone accounts for 0.41 lakh hectares, producing 0.33 lakh tonnes, with an average yield of 810 kg per hectare. In Karnataka, safflower is primarily grown in the districts of Vijayapura, Kalaburagi, Bagalkot, Belagavi, Yadgiri, Raichur, Gadag and Dharwad (Anon., 2022). Safflower is known for its tolerance to cold and drought (Majidi et al., 2011) [11] and its ability to extract soil water that is inaccessible to most other dryland crops (Weiss, 2000) [22] . Despite its significant potential and adaptability to a wide range of agro-ecological conditions, safflower remains underutilized by farmers. This is due to several challenges, including its extended rosette stage, spiny nature, relatively low seed oil content (30-38%), late maturity and susceptibility to various diseases and pests (Sujatha et al., 2008) [19] . The major biotic stresses affecting safflower production include leaf spot diseases caused by Alternaria carthami Chowdhury, Cercospora carthami Sundararaman and Ramakrishnan and Ramularia carthami Zaprometov; wilts caused by Fusarium oxysporum Schlecht. f. sp. carthami and Verticillium alboatrum, Powdery mildew by Erysiphe cichoracearum f. sp. Carthami Milovtzova, Phytophthora root rot and insect pests such as aphids and the safflower fly (Kalpana Sastry and Chattopadhyay, 2005; Singh and Prasad, 2005) [9,17] . Among the various diseases affecting safflower, Alternaria leaf blight and Fusarium wilt are considered the most significant biotic constraints on production. Alternaria leaf blight caused by Alternaria carthami leads to annual yield losses of 25-60 per cent (Singh and Prasad, 2005, Indi et al., 1988) [17,7] with substantial economic consequences for farmers in the Deccan Plateau of India (Rao et al., 2014) [16] . The continuous practice of monocropping and the cultivation of susceptible conventional varieties are key factors contributing to the high incidence of these diseases with reduction in the seed size, seed volume as well as per cent oil content (Kalpana Sastry et al., 1993) [10] . Typical symptoms of the disease are appearance of irregular necrotic lesions on leaves and stem. Dark necrotic lesions of 2-5 mm in diameter are firstly found on hypocotyls and cotyledons. In mature plant, small brown to dark brown concentric spots of 1-2 mm appear on leaves and brown discoloration appear on the stem. As the infection advances, these spots enlarge and coalesce, forming larger necrotic areas that may cover significant portions of the leaf surface. The lesions are frequently surrounded by a yellowish halo, indicating the spread of the pathogen (Mortensen and bergman, 1983; Wagh et al., 2017) [13,21] . Now a day the occurrence of safflower blight is the major threat for oilseed crop production so recent study conducted to evaluate different cultivars/varieties against test pathogen so as to minimize the problem and required cost for management of Alternaria blight disease.

Materials and Methods

Safflower genotypes collected from Agriculture Research Station, Annigeri were screened against leaf blight of safflower, which were maintained at MARS, Dharwad, during rabi 2023-24. Totally 38 safflower genotypes (Table 2) were screened for leaf blight severity including the susceptible checks (Manjira, SSF and A-1). The disease severity was recorded by using 0-9 disease scale (Mayee and Datar, 1986) [12] given below (Table 1).

Results and Discussion

A total of 38 safflower genotypes were evaluated for resistance to Alternaria leaf blight under natural epiphytotic conditions during the rabi season of 2023-24. The results reveal that the genotypes were categorized into six response groups based on their reaction to leaf blight: immune (no infection), resistant (less than 1% leaf area affected), moderately resistant (1-10% leaf area affected), moderately susceptible (11-25% leaf area affected), susceptible (26-50% leaf area affected) and highly susceptible (more than 50% leaf area affected). Among the 38 genotypes tested, none of the genotypes exhibited immune or resistant. Only one genotype ANG 10-4 showed moderately resistant reaction. However, three genotypes found moderate susceptible to Alternaria blight of safflower with (11-25% of the leaf area affected) which includes A 2020, ANG 7-7 and ANG 9-14. ( [18] , highly susceptible genotypes are likely to suffer from severe yield losses and should be avoided in areas with favourable conditions for Alternaria development. These results are in conformity most of the entries/varieties with the findings of those reported earlier by several workers against, Alternaria carthami of safflower (Indi et al., 2004 [8,6,14,3,15,4] .

Conclusion

While field screening of safflower genotypes revealed varying responses to leaf blight, it is crucial to further validate these findings by evaluating the genotypes in multiple hotspot areas for leaf blight. This will help determine their effectiveness as pre-breeding lines.

References

1. Food and Agriculture Organization of the United Nations. Area, production and productivity of safflower. 2020. Available from: www.fao.org/faostat
2. Directorate of Economics and Statistics. Crop-wise area, production and yield of oilseeds in India. 2022. Available from: www.eands.dacnet.nic.in
3. Balode KL, Mane PN, Rathod PK, Deshmukh SN. Evaluation of safflower germplasm for resistance to Alternaria leaf spot. Journal of Oilseeds Research. 2012;29:97-99.
4. Gholve VM, Taware MR, Ghuge SB. Screening of safflower germplasm lines against Alternaria carthami under artificial epiphytotics. Trends in Biosciences. 2015;8(1):61-63.
5. Gilbert GS, Magarey PA, Suiter KA, O'Brien PT. Pathogen diversity and the effects of climate change on disease. Journal of Plant Pathology. 2008;90(2):121-130.
6. Harishbabu BN, RudraNaik V, Hanumantharaya L, Raju SG, Yaragoppa SD. Evaluation of promising lines of safflower for Alternaria tolerance, seed yield and its components. Karnataka Journal of Agricultural Sciences. 2005:803-806.
7. Indi DV, Lukade GM, Patil PS, Shambharkar DA. Estimation of yield losses due to Alternaria leaf spot in safflower under dryland conditions. Pesticides. 1988;22(1):41-43.
8. Indi DV, Murumkar DR, Patil AJ, Akashe VB. Screening of safflower germplasm against Alternaria leaf spot under field conditions. Journal of Maharashtra Agricultural Universities. 2004;2(3):344-346.
9. Kalpana Sastry R, Chattopadhyay C. Major biotic stresses affecting safflower production. Journal of Mycology and Plant Pathology. 2005;35(2):123-130.
10. Kalpana Sastry R, Chattopadhyay C, Varma A. Plant pathology and plant diseases. New Delhi: Oxford and IBH Publishing; 1993.
11. Majidi MM, Tavakoli V, Mirlohi A, Sabzalian MR. Wild safflower species (Carthamus oxyacanthus Bieb.): a possible source of drought tolerance for arid environments. Australian Journal of Crop Science. 2011;5(8):1055-1063.
12. Mayee CD, Datar VV. Phytopathometry. Technical Bulletin-1 (Special Bulletin-3). Marathwada Agricultural University, Parbhani; 1986.
13. Mortensen K, Bergman JW. Cultural variance of Alternaria carthami isolates and their virulence on safflower. Plant Disease. 1983;67:1187-1190.
14. Murumkar DR, Gud MA, Akashe VB, Shinde SK, Kadam JR. Identification of source of resistance to major diseases and pests of safflower. Journal of Plant Disease Sciences. 2009;4(1):107-109.
15. Pawar SV, Dey U, Munde VG, Hulagappa, Nath A. Screening of elite material against major diseases of safflower under field conditions. African Journal of Agricultural Research. 2013;8(2):230-233.
16. Rao VV, Ghosh SK, Patel RK. Economic impact of Alternaria leaf blight on safflower production in the Deccan Plateau. Agricultural Economics Research Review. 2014;27(2):135-142.
17. Singh V, Prasad RD. Integrated management of pests and diseases in safflower. Hyderabad: Directorate of Oilseeds Research; 2005.
18. Sivakumar M, Rajeswari E, Suresh S. Genetic variability and heritability in sunflower (Helianthus annuus L.) genotypes for resistance to Alternaria blight. Plant Archives. 2020;20(1):139-144.
19. Sujatha K, Singh P, Venkatesh B. Late maturity and susceptibility to diseases and pests in safflower. Journal of Crop Improvement. 2008;22(4):91-98.
20. Wagh PS, Patil RR, Deshmukh NS, Sharma MP. Screening of safflower genotypes for resistance to blight. Journal of Crop Improvement. 2015;29(4):215-223.
21. Wagh SS, Suryawanshi AP, Pawar DV. Efficacy of fungicides, bioagents and phytoextracts against Alternaria carthami of safflower in vitro condition. Journal of Pure and Applied Microbiology. 2017:11-15.
22. Weiss EA. Oilseed crops. 2nd ed. Oxford: Blackwell Science; 2000.