Phenological stages and growing degree days for different soybean cultivars [electronic resource].

Includes reference.

Nine soybean cultivars belonging to different maturity groups (MG) in the green house of Crop Physiol. Res. Dept., Giza, 2007 and 2008 seasons. The main objectives were to study the initiation and duration of the different growth stages, growing degree days (GOD) and heat unit efficiency (HUE) in relation to yield and other plant traits. Results indicated that completely unrolled leaf at unifoliolate node (V₁) needed about 191̊ C GOD and this amount was almost constant for cultivars. Number of days (NO) and GOD accumulation for the initiation of reproductive stages varied significantly among cultivars. The earliest cultivar was "Giza 83" (MG II), while the latest was either "Holladay" or "Toano" (MG V). Cultivars of MG IV, i.e., "Giza 21", "Giza 22", "Giza 111" and "Crawford" needed more days to the iniliation of reproductive stages than those of "Giza 35" (MG III) or MGII cultivars. Similar results were obtained when GOO was taken into consideration. There were significant differences among cultivars in the length of vegetative growth, flowering period, pod formation, seed filling and reproductive growth duralions and their degree days sum. "Giza 83" had the shortest stage durations and needed the lowest GOD for full rate of phenological stage. However, "Holladay" and "Toano" had the longest durations and accumulated the most GDD during all developmental stages. Other cultivars were in-between, due to their maturity groups. Cultivars of MG V surpassed the others in plant traits and yield, while "Giza 83" (MG II) had the lowest values of these traits and the rest cultivars were in-between Concerning HUE in seed yield, all cullivars followed the same trend of their productivity with no significant differences between MG IV and MG V cultivars.

Summary in arabic.

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