RESPONSE OF SOME SNAP BEAN CULTIVARS TO SOWING DATES AND GAMMA IRRADIATION

Abstract

The field experiment was carried out during the early winter season of 2011/2012 and 2012/2013 at the experimental farm of the National Center for Radiation Research and Technology, Nasr City, Cairo , Egypt. The aim of this study was to investigate the response of some cultivars of snap bean (Paulista, Xera and Bronco) to gamma irradiation doses (0, 20 and 30 Gy) under different sowing dates (the 1st, the 8th and the 15th of October). The treatments were arranged in a split split plot design with three replicates. The main plot was for the sowing dates, the sub plot was for the cultivars and the sub sub plot was for the different doses of gamma irradiation. The obtained results could be summarized as follows:

5.1. Vegetative growth 5.1.1. Sowing dates At 30 days after planting, the 1st of October significantly increased, leaf number, leaf dry weight and stem dry weight. Plant length, leaf number and leaf and stem fresh weight, number of branches, leaf dry weight and leaf area scored the highest values at the 8th of October. At 45 days after planting, the 1st of October significantly increased leaf and stem fresh weight, leaf and stem dry weight. The 8th of October led to the highest value of plant length, leaf number, stem fresh weight, number of branches and leaf area. At 60 days after planting, leaf number , leaf fresh weight and stem fresh weight in the first season , leaf and stem dry weight, number of branches and leaf area significantly increased at the 1st of October .While plant length increased at the 8th of October. 5.1.2. Cultivars At 30 days after planting, cv. Bronco significantly increased plant length, leaf and stem fresh weight, leaf number in the second season only and leaf area, while cv. Xera significantly increased plant length, number of branches in the second season. At 45 days after planting, cv. Bronco significantly increased plant length, leaf and stem fresh weight, leaf dry weight and leaf area. On the other hand cv. Paulista scored the highest leaf number, stem dry weight and number of branches. Whereas cv. Xera scored the highest leaf number, stem fresh and dry weight. At 60 days after planting, results show that cv. Bronco significantly increased plant length and stem fresh weight in the first season, leaf fresh and dry weight and leaf area in both seasons. Whereas cv. Paulista significantly increased, leaf number , stem dry weight and number of branches. 5.1.3. Gamma irradiation At 30 days after planting, 20 Gy significantly increased plant length, leaf number, stem dry weight and leaf fresh weight in the second season .While 30 Gy increased leaf fresh weight in the second season. At 45 days after planting, 20 Gy significantly increased all growth parameters except leaf fresh weight. The 30 Gy of gamma irradiation dose significantly increased leaf number and leaf fresh weight. At 60 days after planting, 20 Gy significantly increased plant length, leaf number, leaf and stem dry weight , number of branches in the second season and leaf area in both seasons .Whereas 30 Gy increased plant length, leaf number in both seasons and number of branches in the second one and leaf dry weight and leaf area.

5.1.4. The interaction At 30 DAP, the interaction between sowing dates and cultivars showed that seeds of cvs. Bronco and Xera sown on the 1st of October scored the highest leaf dry weight. While seeds of cv. Bronco sown on the 8th of October significantly increased leaf and stem fresh weight, leaf dry weight, number of branches and leaf area. Seeds of cv. Xera sown on the 8th of October significantly increased plant length, leaf dry weight and number of branches. Leaf dry weight and number of branches gave the highest values when seeds of cv. Paulista were sown on the 8th of October. As for the interaction between sowing dates and gamma irradiation. The obtained results showed that the interaction between the 1st of October and 20 Gy significantly increased leaf number and stem dry weight, and 30 Gy increased leaf dry weight. The interaction between the 8th and unirradiated seeds scored the highest stem fresh weight, number of branches in the first season and leaf area. While the interaction between the 8th of October and 20 Gy led to the tallest plant, leaf and stem fresh weight and leaf area. The interaction between the 8th of October and 30 Gy produced the highest values of leaf and stem fresh weight and leaf dry weight, number of branches in the first season and leaf area. Regarding the interaction between cultivars and gamma irradiation, seeds of cv. Xera irradiated with 20 Gy led to the the tallest plant and with 30 Gy scored the tallest plant and number of branches. Unirradiated seeds of cv. Bronco scored the highest leaf fresh weight and leaf area. Seeds of cv. Bronco irradiated with 20 Gy scored the highest values of leaf number, leaf fresh weight and leaf area and with 30 Gy scored the highest leaf fresh weight and leaf area. Respecting the interaction among sowing dates, cultivars and gamma irradiation. It was found that the interaction among the first sowing date, cv. Xera and 30 Gy and with cv. Bronco and 20 Gy led to the highest leaf dry weight. The interaction among the second sowing date, cv. Paulista and all gamma irradiation doses led to the highest number of branches. The interaction among the second sowing date , cv. Xera and all gamma irradiation doses led to the highest number of branches , with 20 Gy led to the tallest plant .The interaction among the 8th of October and unirradiated seeds of cv. Bronco scored the highest stem fresh weight, number of branches and leaf area , with 20 Gy led to the highest leaf and stem fresh weight , number of branches and leaf area and with 30 Gy scored the highest leaf and stem fresh weight, number of branches and leaf area. At 45 days after planting, th