Effect of Sowing Date, Gamma Irradiation and Intercultivar Differences on Growth, Pod Characteristics and Some Endogenous Plant Growth Regulators in Snap Beans

摘要

This study was conducted to compare some vegetative growth characters and yield of two snap bean cultivars sown under open field conditions in Egypt during early winter with the intent of production for export to the European market. The field experiment was conducted in the experimental field of NCRRT, Cairo, Egypt. Seeds of snap bean cvs. Xera and Bronco were irradiated with low gamma ray doses (0, 20 and 30 Gy) before they were sown on different sowing dates (Oct. 1", S* and 15*) in the two consecutive seasons of 2011 and 2012. The experiment was laid out in a split- splh- plot with three replicates, each consisting of two rows (2.5 m long and 0.6 m wide), where seeds were sown 5 cm apart on the top of the rows. Vegetative characters determined were plant height, number of branches, leaf area and leaf fresh and dry weight. Moreover, the concentration of endogenous GAs, auxins and ABA were determined in 30- days old leaves. Along with exportable yield and total yield, average pod weight, pod diameter and pod protein concentration were determined. Resuhs revealed that ahhough vegetative growth attributes were in favor of cv. Bronco but cv. Xera yielded more. Sowing on seeds on Oct. 8* resulted in increased plant length, leaf area, GAs concentration in leaves and enhanced exportable and total yields. Low gamma doses investigated in this study were found to be generally stimulatory. The 20 Gy dose led to the production of maximum number of branches, leaf dry weight and increased GAs and auxins concentrations in leaves and maximized yield. Moreover, the 30 Gy dose resulted in maximum leaf area, leaf fresh weight and increased pod protein percentage.