No abstract

A field experiment was conducted at ICAR Central Potato Research Station Gwalior, MP, during 2015-16 and 2016-17 to study the effect of intra-row spacing, nitrogen levels and date of haulm killing on production of higher proportion of seed size tubers in early bulking variety Kufri Khyati. Treatments consisted of two intra-row spacing (15 cm and 20 cm), two dates of haulm killing (70 and 80 days) and two nitrogen levels (120 and 150 kg ha-1). Treatments were replicated three times with split plot design. Germination percentage was significantly higher in 20 cm spacing (96.76%) over 15 cm spacing (88.12%). Non-significant differences were recorded among different parameters for growth attributes. Significantly highest seed size tuber and total tuber number was recorded in 15cm spacing (405000 ha-1 and 716000 ha-1) over 20 cm spacing (337000 ha-1 and 605000 ha-1) respectively. Non-significant but highest seed size tuber number (432000 ha-1 and 427000 ha-1) was recorded in 15 cm intra-row spacing×80 days haulm killing×150 kg N and 15 cm intra-row spacing×70 days haulm killing×120 kg N respectively. Seed size and total tuber yield (t ha-1) was in significantly higher 15 cm spacing (22.44 t ha-1 and 33.16 t ha-1) over 20 cm spacing (19.81 t ha-1 and 29.84 t ha-1). Significantly higher severe mosaic incidence (0.87%) was observed with 80 days haulm killing over 70 days. Hence 15 cm intra-row spacing×70 days haulm killing×120 kg N was most suitable for getting higher proportion of seed size tubers in Kufri Khyati.

India is the second largest producer of potatoes in the world. Seed is the single most important input in potato cultivation. High seed rate (2.5–3.0 tons/ha), low rate of multiplication, progressive viral degeneration, storage, and transportation are major issues of potato seed production in the country. Potato seed alone accounts for 40%-50% of the total potato production cost, and huge quantities of potentially edible food is put back into the soil as potato seed. The delayed penetration of new improved potato/seed varieties into farmers’ fields due to the slow multiplication rate and frequent seed replacement because of degeneration are associated issues. To circumvent these issues, continuous efforts are being made by potato researchers to develop innovative technologies for quick multiplication of initial healthy breeder’s seed of the released varieties in sufficient quantities to meet the demand in our country. A paradigm shift in potato seed production methods has taken place globally since the early 1900s. Major potato producers of the world have shifted from conventional to hi-tech seed production systems to improve the seed quality and enhance seed multiplication rate. New innovations can overcome many of the problems associated with potato seed production, particularly in tropical and sub-tropical countries. Recent advances in potato seed production systems in India and challenges ahead for seed production are described here.

Potato microtubers plays important role in seed potato production technology as it has great advantage of storage, transport and mechanization due to their little size and reduced weight. Dormancy in potato microtubers is very important and storage conditions as well as size of microtubers influences the dormancy in microtubers. Increasing size of the micro-tuber resulted in significant increase in the viability and sprouting ability of microtubers with reduced durations of dormancy and weight loss at the end of storage. Small microtubers are more vulnerable to storage damage. The larger microtubers lost moisture content more slowly and retained firmness longer when stored at 40C. Development of dormancy during storage strongly affected by the storage condition especially the temperature regime, the presence of light and the relative humidity. The dormancy duration was linearly and inversely correlated with the length of storage. Storage containers and conditions are also important for microtuber storage. Endogenous hormones ABA, ethylene, cyokinin and gibberllic acid play a significant role in tuber dormancy regulation.Microtubers with thick diameter which have passed more times in dormancy and have better functionality than small microtubers with less time in dormancy. Growth regulators like gibberellic acid, thiourea, gibberllic acid + thiourea, randite and carbon disulphide plays significant role in dormancy breaking of microtubers.

The seed potato cost is very important component in total potato production and account for 30 to 70% which varies depending on the country or region. Tuber size is an important factor to decide the seed requirement per unit area. Seed size affects total yield, graded or marketable tuber yields. Standard seed tuber of 25–125 g weight (30–55 mm) is known as seed size tubers in India. Obtaining seed size tuber is important for achieving higher potential of the cultivars. The tuber size profile can be reduced or expanded by altering inter and intra row seed spacing, controlling days of growth by planting late or killing vines/haulm early, regulating inputs like fertilizer and water etc. An ideal combination of plant population, row width, and in-row seed spacing for a particular variety were the major factors for optimizing tuber size. Variation in tuber bulking ability in different genotypes results in variation in proportion of seed size tubers among different varieties. 70–80 days haulm killing found most suitable for getting higher proportion of seed size tubers in high bulking varieties. Proper management of N, P and K fertilizers is considered very important to maximize tuber yield and attain desirable quality. Variability in nitrogen dose/ha was observed which ranged from 100–150 between different regions of the world. Hence proper combination of above Agro-techniques should be adopted in seed production programme as per the region for getting higher proportion of seed size/plantable seed tubers.