The Effect of Water Deficit Imposing Methods on Quantitative and Qualitative Traits of New Potato Cultivar

Water deficiency is the main factor that limits crop production in arid and semiarid regions. Due to limitation in water resources، low efficiency of water in surface irrigation method and irregular rainfall application of sprinkle and triple irrigation methods is inevitable in more regions of Iran. In this respect، it is crucial to employ methods that can improve water use efficiency and do not damage the sustainable production of potato in these regions. Introduction of some potato cultivars that have good capability of yield in deficit irrigation is anopportunity in this case. In previous study new released potato cultivar (Savalan) and three other promising clones had more yield and growing potential compared with Agriacultivar. Therefore، it was necessary to evaluate new cultivar (Savalan) and promising clones in water deficit irrigation. In this respect، as is expected، if cultivars or clones have more tolerance to water deficit they canbe suitable cultivar candidate and germplasms in water critical water conditions in many regions of Iran. This experiment has been conducted in Agricultural and Natural Resources Research Center of Hamedanin split plot design based on Randomized Complete Block in three replications with two factors، including: 1. Water deficit irrigation treatment، 50، 60، 70، 80، 90 and 100% of regular potato irrigation requirement. 2. Three clones accompanied with Savalan and Sante Cultivars. Irrigation system was tape method. Irrigation treatments were established immediately after cultivation of tubers. Water requirement was calculated through corrected vapotranspiration (ETo) determined by Penman-Monteith equation considering 90% water use efficiency. During the growing season، fewgrowing indices including، flowering longevity and harvesting time were recorded along with measurement of dry and fresh root weights. Total yield was measured by selecting randomly of 2 m2in every plot. Harvested tubers were separated as marketable and non marketable. Reducing sugars of tuber were calculated by titration and volume accuracy method. Tow-way analysis of variance (ANOVA) of the data was carried out using SAS software and the means were compared through the Duncan’s Multiple Range Test. multiple analysis of variance of two years demonstrated that water treatment and clone effects were significant at 1% α level on number of stem، time and longevity of flowering، overlapping time، senescing time،fresh and dry root weight، unmarketable yield and total yield. Water regimes had significant effect on reducing sugars but cultivar had not the same effect. Means comparison of main stem showed that providing 80% water requirement had uppermost effect (No average of 6. 16 per plant)، since it didn’t significant difference with 90% and 100% of water requirement. Canopy overlapping time delayed as water supplement decreased. Three clones and Savalan showed similar reaction، but differences were significant as compared with other cultivar (Sante). It seems that supplementing of water requirement as 70% and upper than that have intensified the effect of cultivar on time of flowering and its longevity. Mean comparison of fresh and root dry weight showed significant effect of interaction between cultivar and irrigation levels. 397008-2 clone had more fresh and dry root weight in all irrigation levels as compared to other clones and cultivar. Mean comparison showed that 50 and 60 percent of water requirement increased in tuber. Three higher levels of irrigation regimes (80، 90 and 100 percentage of water requirement) showed the same effect on reducing sugar of tubers and didn’t show significant difference with each other. Supplying water requirement (100%) produced highest yield (6. 25 kg m-2) and didn’t show significant with 80 and 90 percent of water supplement. In this research، there were different reaction between clone/cultivar in main stem and overlapping time for different irrigation regimes. The differences of flowering dateand its longevity between clones in different water treatments demonstrated that although flower longevity of potato is a qualitative trait related to cultivar inherit but it can be affected by environment condition like temperature، light intensity and soil moisture. In this research there have been remarkable changes in reducing sugar of tubers under different irrigation levels. Therefore we can conclude that by determining good strategy for water use management in potato، both water stresses and higher reduction of sugar can be avoided. This result was consistent with previous studies (12، 14 and 18) that evaluated the effect of water stress and water deficiency on qualitative characters of potato. Decreasing 20 percent water requirement of potato، resulted only 0. 7 kg decrease of total yield per square meter. As a result، it can be save more than 40 million cubic meter of water only in Hamedan state every year. Moreover، if we apply some suitable cultivars same as Savalan and other promising clones that have more tolerance to water deficit، it can be more efficient. Totally، the result of the this research showed that decreasing water requirement of potato until 20% not only did not impair the growth and performance of potato but also did not show adverse effects on qualify of harvested tuber. It is also found that Savalan and two clone had more advantage in comparison with others.