Iranian Journal of Seed Research

In addition to common vegetative multiplication, potato crop can be reproduced by true potato seed (TPS). Only the limited number of pests and diseases, which are the most important causes of a decrease in potato production, can be transmitted by true potato seed. Hence, to evaluate the potential of true potato seed in comparison to potato seed tuber and mini tuber, an experiment was conducted in Marvdasht in Fars Province during summer of 2012. Treatments were arranged in a split plot experiment using a randomized complete blocks design with three replications. The main factor consisted of three planting date including 10 July, 20 July, 30 July and sub-factor was allocated to different multiplication methods in 7 levels composed of 3 seed tuber cultivar (Agria, Marfona, Santé), 3 mini tuber varieties, the same as seed tuber varieties, and BSS296 hybrid of true potato seed. The results showed that the effect of the main factor (planting date) on the yield of a tuber, weight of marketable tuber, number of the marketable tuber, and biomass was significant. The interaction effect between main and sub-factors on all characteristics was significant except for yield of the tuber, number of marketable tuber and dry matter traits. The highest yield of a plant was achieved in Santé seed tuber (36.5 t/ha) in the first planting date (10 July) and the lowest one was observed in Marfona mini tuber (19.07 t/ha). The maximum biomass was measured at the first planting date of TPS (338.1 g/plant). The marketable tubers yield in second planting date of TPS was in the lower level than Marfona seed tuber however, it was placed at the same statistical level with other seed tubers but it was better than all mini-tubers. The results of this study suggested that TPS was better than mini-tubers in mostly measured characteristics, but TPS in comparison to different seed tubers at three mentioned planting date indicated variable situations.

Extended Abstract
Introduction: Sweet corn (Zea mays var. saccharata) is a corn variety that is distinguished from other varieties due to the presence of genes that affect starch production in the endosperm. Given that the most of plants including sweet corn face with problems such as non- uniform germination and poor seed emergence in the early stages of germination. Thus, the use of organic stimulants is one of the ways to reduce the harmful effects of non-biological stresses, increase seed germination, uniform appearance and increase their yield and quality. The present study was carried out to investigate the effect of different concentrations of chitosan on seed germination and some biochemical traits of sweet corn under osmotic potential conditions.
 Materials and Methods: To investigate the effect of chitosan and osmotic stress on germination and biochemical parameters of sweet corn, a factorial experiment was conducted in a completely randomized design with four replications at the Seed Technology Laboratory, Faculty of Agriculture, Yasouj University in 2017. The first factor was osmotic stress at 0, -3, -6, and -9 bar osmotic potentials and the second factor was pre-treatment at five levels of chitosan zero, 0.25%, 0.5%, 0.75% and 1% and one level of distilled water. The seeds were immersed in the desired solutions of chitosan for 3 hours at 25 °C and under dark conditions, and then the pre-treated seeds were germinated under standard germination condition. In each petri dish, 25 seeds were placed on a filter paper and osmotic potential was applied using polyethylene glycol 6000. Seed germination was carried out in the germinator at 25 ± 1 ° C for 7 days under dark conditions. The germination traits and biochemical traits were measured according to standard methods.
Results: Osmotic stress reduced germination percentage and germination rate, seedling vigour length index, germination uniformity coefficient, allometric coefficient, and soluble protein content and also increased the mean germination time, proline, soluble sugar content and hydrogen peroxide. Pre-treatment of seeds with a concentration of 0.5% chitosan increased protein, proline, and soluble sugars content at all osmotic stress levels. At the osmotic stress levels, the highest and lowest levels of hydrogen peroxide respectively were observed in 0.5% chitosan treatment and distilled water treatment. The results showed that pre-treatment with 0.5% chitosan increased germination percentage and rate and seedling vigour length index, and also reduced the mean germination time and malondialdehyde. Pre-treatment of seed with zero and 1% chitosan led to reduction in some of the germination and biochemical traits in comparison with 0.25, 0.5, and 0.75% chitosan.
Conclusions: The results showed that seed treatment with 0.5% chitosan could reduce the harmful effects of osmotic potential on some germination and biochemical traits in sweet corn seedlings and improve seedling growth.
 
Highlights:
1-Chitosan increases the germination percentage and germination rate.
2-Chitosan increases soluble sugars, proline, and soluble protein.
3-Chitosan reduces the amount of malondialdehyde and hydrogen peroxide.