Evaluation of new potato cultivars response to autumn and winter cultivation seasons in tropical regions

 Potato production in tropical and subtropical regions of Iran is always associated with high temperatures in bulking stage in winter cultivation and also low temperatures in bulking stage in autumn cultivation. One of the most important strategies to mitigation these chalenges is to identify and introduce compatible cultivars from early to mid-early maturity groups and determine the effects of cultivation seasons on cultivars, which is the subject of this study.

in order to introduce new compatible cultivars with the autumn and winter cultivation season, this study was performed as a split plot based on a randomized complete block design with 3 replications in the years 2019-2020 and 2020-2021. In this study, cultivation season at two levels (autumn and winter cultivation) was considered as the main factor and cultivars at 10 levels including Concordia, Ottawa, Georgina, Ribera, Coronada, Colomba, Sylvana, Challenger, Atosa and Sante) were considered as sub-factor. The measured traits included the average number of tubers per plant and mean tuber weight per plant by marketable and non-marketable, weight percentage of non-marketable tubers, marketable yield, tuber dry matter content, dry weight of plant organs separately (haulm and tubers), biological yield and harvest index.

The response of the studied cultivars to autumn and winter cultivation seasons was very different. The highest tuber weight per plant was obtained from Colomba cultivar in autumn cultivation of first year and Ottawa cultivar in winter cultivation in both years. The lowest weight percentage of non-marketable tubers belonged to Colombus cultivar in autumn cultivation of the first year and winter cultivation of the second year, but the highest weight percentage of non-marketable tubers related to Georgina and Ribera cultivars in winter cultivation in both years and Challenger cultivar in autumn cultivation of second year. Sante, Challenger, Atosa and Ottawa cultivars in autumn cultivation and Challenger, Sante and Atosa cultivars in winter cultivation had the highest tuber dry matter content. Production and quality of potato tubers are affected by several factors, including cultivar and temperature stresses (Aien et al., 2017). The highest harvest index (78.4%) was obtained from Colomba cultivar in autumn cultivation. Georgina, Coronada and Atosa cultivars produced the highest haulm dry weight in winter cultivation. In the present study, plants in the winter cultivation in the first year from the beginning of the bulking stage and in the second year from the middle of the bulking stage were exposed to high temperatures. High temperatures reduce the production of assimilates in potatoes and decline the partitioning of assimilates to the tubers and increase their movement towards the haulm (Aien et al., 2017; Lizana et al.,2017). Marketable tuber weight per plant, harvest index, biological yield in both years and tuber dry matter percentage in the first year had a positive and significant correlation with marketable yield. However, the correlation between the number and weight of non-marketable tubers per plant, weight percentage of non-marketable tubers and haulm dry weight with marketable yield was negative and significant. Colomba, Ottawa and Sante cultivars in the first year of autumn cultivation with marketable yields of 44.23, 44.19 and 42.94 tons/ha, respectively, and in the second year by 42.35, 40.65 and 40.37 tons/ha, were superior than other cultivars. Also in winter cultivation, Ottawa and Colomba cultivars were superior with production of 46.1 and 42.36 tons/ha in the first year and by 48.4 and 43.02 tons/ha in the second year. Therefore, Colomba, Ottawa and Sante cultivars are recommended for autumn cultivation and Ottawa and Colomba cultivars for winter cultivation in the tropical regions of south of Kerman.