Evaluation of Effect of Physiological Growth Indices of Potato (Solanum tuberosum L.) Cultivars in Farmian and Jolgeh- Rokh Regions

The importance of potato (Solanum tuberosum L.) is due to its high energy content. Potato is the world's fourth most important crop after wheat, rice and maize and plays a crucial role in human diet because of its high content of protein, essential amino acids, vitamins and minerals. Potato cultivars are cultivated in different climatic conditions. A suitable cultivar should be compatible with the region and have an acceptable yield. As to growth period length, potato cultivars are divided into early, intermediate and late maturing cultivars. Agria and Fontane cultivars with the highest cultivation area in Khorasan-Razavi province are considered as the main cultivars used in chips production. Sen et al., (2014) found that leaf area index increases 47 days after emergence. In addition to leaf area, the durability of the leaves and their arrangement on the stem affects potato final tuber yield. It has been reported that there is a correlation between leaf area durability and tuber yield. Ahmed et al. (2000) stated that tuber formation occurs in the early stages of growth about three weeks after tuber planting. Considering the lack of sufficient research on potato growth response to climatic conditions and given the importance of high-quality potato production the current study was aimed to evaluate the effect of climate conditions on Agria and Fontane potato cultivars with respect to growth indices under climatic conditions of Jolgeh-Rokh and Fariman regions.

This experiment was conducted to evaluate growth and physiological indices of Agria and Fontane cultivars grown in Jolgeh-Rokh and Fariman regions during 2005-2006. First, soil samples were collected to determine soil physicochemical characteristics. The experiment was a randomized complete block design arranged in factorial. The treatments consisted of two different regions (Jolgeh-Rokh (Razaghi and Khazaee fields) and Fariman (Mahdavi and Shariati fields)) and two potato cultivars (Agria and Fontane). The data were collected by random sampling method. For analyzing farm management, information on all agronomic practices such as land preparation, seeding, irrigation, fertilization, chemical pesticides, required work force, etc. were collected through interviews and questionnaire. During the growing season, every three weeks, three plants were harvested from each field and plant height, leaf area, shoot dry weight and tubers fresh and dry weight were determined. Crop growth rate and relative growth rate were calculated. The data were analyzed using SAS 9.1.

From the results the Fontane cultivar produced more tubers (40%) than Agria cultivar. The maximum and minimum tuber yields were obtained from Khazaee and Shariati, respectively. 135 days after emergence, the highest plants were related to Fontane cultivar. Furthermore, the highest plants were observed in Khazaee filed. In this regard, it has been reported that plant height is more affected by genetic background and is less affected by the nutritional conditions. The highest leaf area index was related to Fontane cultivar. The maximum leaf area index values were obtained from Khazaee and Mahdavi fields. Leaf area index reached to its maximum 90 days after planting and then started to decrease due to canopy closure, shading, leaf senescence and abscission. Moreover, leaf dry weight linearly increased and reached to its maximum 90 days after planting and the started to decrease. The maximum leaf dry matter accumulation was related to Fontane cultivar. Moorby (2005) stated that tuber growth is the main factor controlling photosynthesis in potato, and reported that any change in tuber growth rate changes dry matter production and accumulation. The maximum and minimum crop growth rate values (90 days after emergence) were observed in Fontane and Agria cultivars, respectively.

Considering the importance of potato production in Iran, identification and releasing high yielding and compatible potato varieties is necessary. Overall, the results showed that Fontane cultivar was better than Agria in terms of total yield, crop growth rate, tuber weight and tuber growth rate when grown in Jolgeh-Rokh region. Therefore, Fontane is recommended for this region. In addition, the maximum dry matter percentage, as an important trait for industries, was related to Jolgeh-Rokh region.