Growth, biochemical constituents and yield of snap bean as influenced by low gamma irradiation doses under different sowing dates

Abstract

The field experiment was conducted within the two successive growing seasons of 2008/2009 and 2009/2010 to study the effect of low gamma irradiation doses (0, 10, 20, 30, 40, 50 and 60 Gy) on growth and productivity of snap bean cv. Bronco grown in 3 sowing dates 1st, 15th and 30th of October in the two seasons. Data revealed that the early sowing date on 1st of October showed the highest seedling emergence percentage but the lowest seedling emergence rate in the field, 30 Gy doses produced the highest seedling emergence percentage in the two seasons. Vegetative growth, i.e., plant height, leaf number, leaf area and plant dry weight at 50 days after planting recorded significantly the highest values at the early sowing date on 1st of October in the two seasons. With respect of gamma irradiation doses, all the previously mentioned parameters of plant vegetative growth recorded the highest values with 30 Gy. However the late sowing date in the two seasons positively increased total sugars in leaves. The early sowing date increased the total chlorophyll reading in leaves and protein in green pods. Also the early sowing date on 1st of October combined with 30 Gy dose led to the highest auxins, gibberellins, cytokinins values while it gave the lowest values of abscisic acid. The early sowing date gave the highest percent of fruit set, the influence of gamma irradiation on fruit set, 20 or 30 Gy doses gave the highest fruit set percentage. Also the early sowing date in both seasons gave the highest number of pods and pod yield per plant and feddan. In addition, 30 Gy of gamma irradiation doses recorded the highest values of pod number and pod yield per plant and feddan and marketable yield per feddan. Gamma irradiation at 30 Gy dose recorded the highest values of protein in green pods and increased total sugars in leaves. Yield per feddan significantly (0.997) correlated with seedling emergence percent, plant height (0.996), leaf number (0.928), leaf area (0.980), dry weight (0.978), chlorophyll reading (0.953), fruit set (0.995), number of pod (0.972), total protein (0.998) and total fiber (-0.935).