KANWAR, H.S.MANOHAR, LAL2018-05-192018-05-192018-04http://krishikosh.egranth.ac.in/handle/1/5810046746ABSTRACT The present investigation entitled “Studies on seed production technology of onion (Allium cepa L.) under changing climatic conditions in mid hills of Himachal Pradesh” was carried out during Rabi season of 2014-15 and 2015-16 in the Experimental Research Farm and Laboratory of the Department of Seed Science and Technology, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh using cv. ‘Palam Lohit’ under four experiments. The first experiment on ‘Effect of mulching and date of bulb transplanting on seed production of onion’ comprised of twenty treatment combination of mulching (black polythene mulch, silver-black polythene mulch, crop residues and no mulch) and dates of bulb transplanting (1st September, 15th September, 30th September, 15th October and 30th October) with spacing 45 × 45 cm. Second experiment on ‘Effect of mulching and planting geometry on seed production of onion’ comprised of sixteen treatment combinations of mulching (black polythene mulch, silver-black polythene mulch, crop residues and no mulch) and planting geometries [(45+45) × 45 cm, (60+30) × 45 cm, (45+45) × 30 cm and (60+30) × 30 cm]. Third experiment on ‘Effect of mulching and date of seedling transplanting in seedto- seed method of onion seed production’ which comprised of twenty treatment combination of mulching (black polythene mulch, silver-black polythene mulch, crop residues and no mulch) and dates of seedling transplanting (1st August, 15th August, 1st September, 15th September and 30th September) with spacing 45 × 45 cm. The experiments were laid in a Split Plot Design in field and Completely Randomized Design (Factorial) in laboratory which were replicated thrice. The observations were recorded on growth characters viz. plant height (cm), days to 50 per cent flowering, number of umbels per plant, number of umblets/umbel, umbel diameter (mm) and length of flowering stalk (cm); seed yield characters viz. number of seeds per umbel, number of seeds per plant, seed yield per plant (g), seed yield/plot (g) and seed yield/ha (kg); and seed quality attributed viz. 1000 seed weight (g), electrical conductivity of seeds (μSm-1), seed germination (%), speed of germination, seedling length (cm), seedling fresh weight (mg), seedling dry weight (mg), seedling vigour index-I and II. In the fourth experiment entitled ‘Impact of climate change on seed yield of onion’, data on various weather parameters (1985-2014) and onion seed productivity (1988-89 to 2013-14) was collected for linear regression and correlations analysis to study the trends of various weather parameters as well as their relationship with productivity. First experiment revealed that the treatment combination 15th October and black polythene mulch exhibited maximum values for almost all the growth characters, seed yield and seed quality attributes. The treatments have non-significant effect on electrical conductivity. Treatment combination 30th October and black polythene mulch was at par with best treatment combination for seed yield (per plant, per plot and per hectare). Second experiment revealed that treatment combination black polythene mulch and (45+45)×45 cm planting geometry was found superior for all the growth characters, seed yield attributes like number of seeds per umbel, number of seeds per plant and seed yield per plant; and seed quality attributes. On the other hand, onion bulbs planted in (45+45)×30 cm planting geometry on black polythene mulch resulted in higher seed yields (per plant, per plot and per hectare). Third experiment revealed that onion seedling transplanted on 1st September on black polythene mulch performed best for almost all the growth characters, seed yield attributes and seed quality characters. Lastly, the fourth experiment revealed that annual temperature showed an increasing trend in study area; whereas, the annual total rainfall as well as relative humidity showed a decreasing trend. The onion seed productivity over 26 years (1988-89 to 2013-14) showed a fluctuating pattern with an overall decreasing trend. Finally, in bulb to seed method 15th October date of bulb transplanting with (45+45)×30 cm planting geometry on the black polythene mulch; and in seed-to-seed method 1st September date of seedling transplanting on black polythene mulch may be recommended for commercial seed production of onion cv. ‘Palam Lohit’ after verification of results in the farmers field to neutralize the adverse effect of the climate change.ennullThesis