INTRODUCTION Potato is an important starchy food crop belonging to the family solanaceae. It is cultivated in different parts of India widely. It seems to be originated from South America more preciously from mountains of southern Peru and Bolivia. Potato is the world's fourth-largely consumed food crop following rice, wheat and maize (Gupta and Modgil 2008). Potato occupies an area of 20.64 million hectares in the world with an annual production of 392.96 million tons and an average productivity of 19.03 tons per hectare. Potato is a short duration crop widely grown all over the world. India ranks first in the area (2.17 m ha) and production (51.28 m tons) with an average productivity of 23.63 t/ha. Potato production in India expanded from 2.7 million tons in 1961 to 51.28 million tons in 2020. The top producers of potato in the world are India (28.01%), China (23.90%) and Russia (8.1%). Potato is grown almost in all the states of India. Major potato growing states are Uttar Pradesh, West Bengal, Bihar, Gujarat, Madhya Pradesh, Punjab, Assam, Chhattisgarh, Jharkhand and Haryana. In West Bengal potato occupies an area of 4.6 lakh hectares with a production of 13.16 m tonnes per annum. The potato is susceptible to many diseases which consistently cause yield losses in potato production. Late blight, early blight, Phoma leaf spot, common scab, black scurf, dry rot and wilting are the important fungal diseases in West Bengal. Among these diseases, the most commonly occurring and destructive foliar diseases are late blight and early blight in West Bengal. Severity and incidence caused by late blight pathogen varied from 1.50 to 60.00% and 2.00 to 75.00% respectively and the yield declined up to 65.00% (Bisht et al., 1997). The disease incidence of early blight varies from 19.10% to 30.50% and yield loss up to 40.00% from year to year depending upon the weather condition and varieties grown. The crop losses can be reduced following suitable chemical control measures. But chemical control measure is hazardous to human being and environment and repeated use of chemical fungicides develop resistance to the pathogens. The management of these diseases using various cultural practices is more acceptable and ecologically viable. Keeping these views in mind the present experiment was conducted to find out suitable potato cultivar which will be more resistant to both of these diseases. MATERIALS AND METHODS The experiment on the varietal reaction of potato against early blight and late blight diseases was conducted during the Rabi season in the District seed farm ‘C’ Unit, Bidhan Chandra Krishi Viswavidyalaya, Kalyani, Nadia, West Bengal during the year of 2019-2020 and 2021-2022. Ten different varieties of potato were selected for the studies viz. Kufri Garima, Kufri Neelkantha, Kufri Pushkar, Kufri Chipsona-3, Kufri Jyoti, Kufri Himalini, Kufri Khyati, Kufri Gaurav, Kufri Lima and Kufri Pukhraj. Recording of data: Data was recorded to determine disease incidence and severity after appearance of the diseases in the field. Seventeen plants were selected randomly in each plot of each variety of potato crop. The observations were made at seven days interval after first appearance of the diseases. For measuring the disease severity lower, middle and upper leaf of each plant were selected and labelled for subsequent observations. Then the percentage of leaf area infected of each leaf was recorded. To determine the disease incidence total no. of plants and no. of infected plants in each plot were recorded and ultimately used this data to calculate the disease severity following the formula. Disease incidence (%) = (No. of plant infected)/(No. of plant observed) × 100 The descriptive (0-6) scale (Campbell and Madden 1990) used for the assessment of late blight disease intensity and (0-5) scale (Ganie et al., 2013) used for the assessment of disease intensity of early blight of potato (Table 1). The percent disease index (PDI) was calculated using the formula according to the Mc Kinney (1923). PDI = (Sum of numerical ratings)/(Total no.of leaves observed ×highest disease rating ) × 100 RESULTS AND DISCUSSION Here ten varieties of potato were tested against late blight and early blight diseases of potato under field condition. The varieties exhibited different types of reactions, i.e.- a) highly resistant -Kufri Himalini, Kufri Kesar, Kufri Chipsona-3; b) moderately resistant - Kufri Gaurav, Kufri Khyati, Kufri Neelkantha, Kufri Garima; c) susceptible - Kufri jyoti, Kufri Pukhraj; and d) highly susceptible - Kufri Pushkar; against both these diseases. Kufri Himalini (T5) exhibited highly resistant reaction to late blight in terms of lower disease incidence (36.42%) and severity (16.21%) with yield 45.00 ton/ha followed by Kufri Kesar (T10) where per cent disease incidence and severity were 44.56 and 20.94% respectively at 73 DAP with a production of 44.50 t/ha. Higher disease resistance reaction was also exhibited by kufri chipsona-3 (T4) where percent disease incidence and severity were 46.69 and 21.35 respectively at 73 DAP and 44.10 t/ha yield. Kufri Gaurav (T8), Kufri Khyati (T6), Kufri Neelkantha (T9) and Kufri Garima (T1) were moderately resistant in terms of slightly higher disease incidence i.e. 58.20, 66.17, 67.15 and 68.29% respectively and severity i.e. 32.10, 41.77, 42.31, 42.49% respectively with lower yield i.e. 43.90, 42.50, 42.44 and 42.00 t/ha respectively compared to Kufri Himalini, Kufri Kesar and Kufri Chipsona-3. Kufri Jyoti (T2) and Kufri Pukhraj (T7) were susceptible to this disease and produced 31.70 t/ha and 31.45 t/ha respectively. But among theses varieties Kufri Pushkar (T3) was highly susceptible due to higher disease incidence (100.00%) and disease severity (66.17%) (Table 2 & 3). Mohsan et al. (2016) also reported that one of the potato varieties, FD 73-73 was highly resistant to late blight disease due to low infection (10%) which was similar with the result of this experiment where Kufri Himalini, Kufri Kesar and Kufri Chipsona-3 were also highly resistant to this disease. Same trend was also observed against early blight disease. Kufri Himalini (T5), Kufri Kesar (T10) and Kufri Chipsona-3 (T4) exhibited highly resistant reaction due to lower disease incidence i.e. 19.29, 19.89 and 21.13% respectively and disease severity i.e. 9.19, 10.23 and 11.52% respectively with yield i.e. 45.00t/ha, 44.50t/ha and 44.10 t/ha respectively. Kufri Khyati (T6), Kufri Gaurav (T8), Kufri Neelkantha (T9) and Kufri Garima (T1) were moderately resistant and Kufri Jyoti (T2), Kufri Pukhraj (T7) and Kufri Pushkar (T3) were treated as highly susceptible due to higher disease incidence i.e. 54.29, 56.23, and 57.23% respectively and disease severity i.e. 27.14, 27.23, and 29.13% respectively compared to other cultivars (Table 4 & 5). These findings are similar with Dey et al. (2012) who reported that Kufri Jyoti and Kufri Ashoka showed less disease incidence (4.12 and 12.36%) and disease intensity (1.87 and 3.20%) at 14 days after first appearance of the disease in the field. But here almost similar type of result was found in three varieties viz., Kufri Himalini, Kufri Kesar and Kufri Chipsona-3 after 28 days of appearance where disease incidence and disease severity ranging 19.29 - 21.13% and 9.19 to 11.52% respectively which was slightly higher than referred result. So these varieties may be accepted for cultivation with proper management practices.