Evaluation of introduced potato colons during spring and fall cropping systems for quantitative and qualitative traits, multiplication rates and storability of the tubers

Identifying potentials of new potato genotypes and required growth conditions for expression of the desirable traits are necessary steps for investment on this crop production. Processing, table qualities and storability of the tubers of the new variety are the main factors for successful introduction. Presence of natural variation among potato colons is the prerequisite for variety selections for adaptation to environmental conditions, agricultural practices and tuber shelve-life. Objectives of this study were to evaluate yield, storability and propagation rate of colons under filed conditions. Eight new potato colons were propagated through in vitro culture, produced mini-tubers under the greenhouse conditions and are planted in experimental fields in Karaj, Hamadan and Jiroft provinces. Yield, visual traits, dry weight and tuber storability of colons were compared with those of control varieties. In year 2009 and in Karaj experimental station, some of the control varieties had lower tuberizations and yields compared to the colons, however, the traits were comparable to those of controls. Lower plant heights and life lengths of colons compares with control varieties. Probably, many more number of days to maturities observed amog colons may be related to the prolong growth periods of colons; however, maturity days of some colons may be actually longer than control varieties. Dry matters of the 3 colons were higher that of Santeh, while two other colons (533 and 780) had comparabily lower dry matters. It was known that normally there is a negative correlation between tuber dry matters and tuber yields of vaieties. Dormancy periods of tubers of colons were longer than that of Santeh variety. Most of the colons had a delayed-maturity days compared with that of Santeh (early maturing variety). Reminding that there has been positive relationship between dormancy period and days to maturity. In year 2010-2011, the trial separated colons 783, 782, 777, 776, 533 and 531 from the rest of the colons. Multiplication rate and tuber yield of potato colon 782 were superior to those other varieties, therefore it must be superior as well to the rest of the colons. Colon 777 had an average tuber weight, high multiplication rate and without yield reduction compared with conrol varieties, was considered as the second best colon. Colon 2 had a lower yield, but produced higher number of tubers per squre meter, providing with adequate amounts of fertilizer, it would be a suitable colon for minituber production. Colons with long leaves (781, 777 and 782) are better deflect irradiated heat from sun by reduce leaf boundry layers and remain cooler for optimum assilimation. In Hamadan research station, except for high yielding colon 780, numbers of tubers in various classes produced by different colons were silimar to that of Santeh. Number of tubers produced by five different colons were comparable to that of the Santeh. Yields of colon 776 and 780 were significantly superior to the control varieties and yield of colon 533 was comparable to two control varieties. Dry matter percentages of 3 colons were higher than Santeh. Negative correlation between tuber dry matters and tuber yields was recorded. Dormancy periods of the tubers produced by the colons were longer than that of the Santeh. Maturity days of the colons tends to be shorter than that of Agria but comparable to that of Santeh. Only correlations between total yields and weights of large and medium tubers were significant, therefore, small tubers had not significant effects on the total tuber yields. Positive correlation between number of large tubers and malformed tubers suggested after increase in certain tuber sizes, during tuber bulking period, there will be good chances of production of the malformed tubers. In years 2009 and 2010 in Jifort research station, performances of nano-silver pre-treated (specially treated with 75 ppm( tubers of the colons depended on the type of the colon tested. Tuber treated with 75 ppm nano-silver in few cases (532, 533 and 776) rendered in increased individual tuber weights and in more cases the treatment increased (781, 780, 777, 776, 533 and 532) the colons' tuber weights comparable to those of the control varieties. Contrary to this, preteated tuber seeds with 25 and 50 ppm nano reduced individual tuber weights of the colons. In year 2011, exceptionally, single tuber weights of the colon 533 were higher than that of the best control potato variety. Nano-silver (specially with 75 ppm) treated seed tubers of colon 776, 779 and 780 either made tuber weights similar or increased them in compared with those of the controls. Genrally, multiplication rates of the colons were not influenced by chemical treatments. Finally, during two years of the testing, tuber yield of colon 776 treated with 50 ppm nano-silver made first or second rank among other colons. However, tuber yield of colon 533 treated with 75 ppm for one year was comparable to that of Santeh and also its yield was significantly superior compared with Agria and Arida varieties