evaluation of tuber yield and growth indices of potato genotypes in mountain and plain conditions in golestan province

potato (solanum tuberosum l.) cultivation in two different climates causes difference in its growth process.the most frequently used indicators of growth for plants are the tuber growth rate (tgr), crop growth rate (cgr) and leaf area index (lai). shoot dry weight is the easiest, quickest and least costly component to measure the competitive features of plants.the results of some studies showed that lai is an appropriate criterion for estimating the degree of crop yield variation. ezekiel and bhargava, stated that a higher potato yield in summer compared to autumn is because of a longer growing season and higher nar. this study has been carried out to investigate the physiological parameters affecting the performance of fourteen potato genotypes based on the growth indices in different stages of the plant growth period from germination to maturity, as well as the tuber yield in two different weather conditions, i.e. shahkooh mountain (for spring planting) and gorgan plain (for autumn planting) during 2007-2010.this experiment was carried out in the framework of randomized complete block design with three replications and nine breeding population (genotypes) called 396151-29, 397009-7, 397007-9, 397007-11, 397097-14, 397009-3, 397009-8, 396151-7, 396140-14 together with the varieties of agria, sante, satina, burrena and marella, with a total of 14 treatments with six 4-meter lines, with 75 cm row spacing and 25 cm plant spacing on lines in ridge and furrow pattern. the results showed that the highest crop growth rate were obtained by 397097-14 (13 g/m2/day) and 397009-7 (20.1 g/m2/day) at autumn and spring planting, respectively. the highest leaf area index was 3.60 for genotypes 397009-3 and 3.36 for 396140-14 at spring and autumn planting, respectively. at the end of the growth period when the leaf area index was decreasing, the difference among genotype at spring sowing increased.genotypes 397009-7 and 397009-3 produced the highest yields (27056 and 28446 kg/ha) at autumn and spring planting, respectively. genotype 397009-7 was considered the best genotype for producing 11.9 and 12.5 tuber per plants at autumn and spring sowing, respectively. in this 3-year experiment the average yield in spring planting (shahkooh) was higher than autumn planting (gorgan). it was also shown that the genotypes had different thermal needs, which could have been due to changes in air temperature in different years and places, which has ultimately led to changes in the plant growth rate and crop yield. the results of the present study indicated that genotype 397009-3 having higher leaf area index and crop growth rate could produce higher dry matter and store more and as a consequent, they justified its higher economical yield.