120 Indian Journal of Agricultural Sciences 89 (2): 288–92, February 2019/Article Standardization of plant density and intra-row spacing to maximize seed size tubers in two potato cultivars (Solanum tuberosum) grown in northern hills RAJESH K SINGH 1 , ASHWANI K SHARMA 2 , TANUJA BUCKSETH 3 , JAGESH K TIWARI 4 and S K CHAKRABARTI 5 ICAR-Central Potato Research Institute, Shimla, Himachal Pradesh 171 001 Received: 21 April 2018; Accepted: 05 September 2018 ABSTRACT To overcome the problem of oversize tubers, three planting densities (80000, 100000 and 133333 plants/ha) were evaluated at 25, 20 and 15 cm intra-row and 50 cm inter-row spacing, in two late blight resistant potato (Solanum tuberosum L.) cultivars, viz. Kufri Himalini and Kufri Girdhari during the kharif season under hill conditions. At the maximum plant density (133333 plants/ha) obtained with closer spacing (50 × 15 cm), the proportion of extra large (>150 g) tubers was reduced from 23.5 to 12.4% in cv. Kufri Himalini and from 17.4 to 10.4% in cv. Kufri Girdhari. Besides, an increase in the proportion of seed size (20-80 g) tubers from 33.6 to 43.9% was also recorded. The yield of extra-large tubers (>150g) came down from 43 to 30% along with 10% increase in the yield of seed size (20-80 g) tubers. Key words: Ground cover, Plant density, Plant vigour, Potato, Seed size, Tubers 1 Head, Division of Seed Technology, 3 Scientist (e mail: tanujagbpuat@gmail.com), Division of Seed Technology, 4 Senior Scientist, Division of Crop Improvement, 5 Director, ICAR-CPRI, Shimla. Principal Scientist and Head, Division of Seed Technology ICAR-CPRS, Kufri. Optimizing plant density and seed size is the most important issue of potato production due to its direct effect on seed cost, plant development, yield and quality of the crop. Seed constitutes a major and important input in potato (Solanum tuberosum L.) cultivation; non-availability of quality seeds has been reported to be a major factor for low potato productivity in India (Rana et al. 2013). On account of vegetative propagation, the requirement of seed potatoes (tubers) is voluminous and accounts for 40-50% of the total production cost (Kushwah and Singh 2008, Sharma and Singh 2010). The production cost may still be higher in the high hills, where, a major proportion of the potato harvest falls in large and extra-large grades on account of long crop season coupled with long day conditions (Sharma and Kumar 2014). Small tubers compared to large ones are highly preferred by the farmers to reduce the seed costs (Horton, 1987). Small tubers are known to reduce the seed requirement by ~50% and consequently, decline the cost of cultivation by about 25% (Arsenault et al. 2001). Late blight is one of the major diseases in the hilly areas, where potato is grown mainly during kharif season. To circumvent the problem, development of late blight resistant cultivars is an important approach which also saves the cost of chemicals. On these lines, the ICAR-Central Potato Research Institute, Shimla released two late blight resistant cultivars, viz. Kufri Himalini and Kufri Girdhari during the years 2007 and 2011, respectively. Both the cultivars besides being resistant to late blight have high yield potential over the existing cultivars of potato in the region (Joseph et al. 2007, 2011). Being resistant to late blight, these cultivars are becoming popular amongst the farmers of the hilly areas (Sharma and Pandey 2015). Although, the cultivar Kufri Himalini is performing well in all the potato growing regions of India, due to the longer crop duration in the high hills, a major proportion of the produce falls in large and extra- large grades (Sharma and Pandey 2015). Such, large-sized tubers are not preferred either for seed or for table purpose. Keeping in view the problem of over-sized tubers with late blight resistant cultivars in the hills, an attempt was made to improve the proportion of seed size tubers through the manipulation of planting density/crop geometry. MATERIALS AND METHODS A field study was conducted in split plot design with three replications during the kharif seasons of 2013 and 2014 at ICAR-Central Potato Research Station, Kufri (Fagu Unit), Shimla, which is located at 2700 m above mean sea level. Seed tubers (40-60 g) of potato cultivars Kufri Himalini and Kufri Girdhari collected from last season (Sept. harvest) were planted at three plant densities, viz., 80000 (D1), 100000 (D2) and 133333 (D3) plants/ha, representing the intra-row spacing of 25, 20 and 15 cm, https://doi.org/10.56093/ijas.v89i2.87020