Enhancing the growth and yield of the common bean cultivar 'Nebraska' under high temperature conditions by combining different magnesium levels with arginine, glycine, and melatonin.

BACKGROUND

One of the most widely consumed legumes worldwide is the common bean. Abiotic stress factors such as heat stress significantly reduce crop productivity, and climate change models predict rising temperatures in many agricultural regions. In the 2021 and 2022 seasons, two field trials were conducted in the Wadi El Natrun Region, El-Behera Governorate, Egypt. A combined split-plot of the data was statistically evaluated using a Randomized Complete Block Design (RCBD). The following seven treatments were tested in this study: arginine at 1.25 and 2.5 mM, glycine at 12.5 and 25 mM, melatonin at 50, 100 µM, and control (distilled water). Magnesium fertilization treatments were added to the irrigation water at varying levels (0, 9.52, 19.05 and 28.57 kg/ha). Measurements of the physical and chemical characteristics, mature pods and seeds parameters, and vegetative features were made. This study aimed to ascertain whether common bean plants grown under natural field conditions in early April, thus exposes the plants to increasingly higher temperatures during critical reproductive stages towards late spring and early summer, particularly between May and July, when average daily temperatures in Egypt tend to exceed optimum values for common bean growth. This could benefit from the application of arginine, glycine, and melatonin to improve their development and yield, taking into account varying magnesium levels.

RESULTS

Melatonin at 100 µM produced the highest values across all measured characteristics, while the control treatment consistently showed the lowest values across all magnesium levels. Regarding magnesium levels, the highest values for all traits were observed at 28.57 kg ha⁻, whereas the lowest values were recorded at 0 kg ha⁻. There was a significant interaction between foliar application treatments and magnesium levels for plant height, potassium, phosphorus, and magnesium content. For each trait with a significant interaction, melatonin at 100 µM combined with magnesium at 28.57 kg ha⁻ resulted in the highest values, whereas the control treatment with 0 kg ha⁻ magnesium yielded the lowest values. Melatonin 100 µM under Magnesium level (28.57 kg ha⁻) increased plant height to 65.46 cm, chlorophyll content to 43.41 SPAD units, and seed yield per plant to 26.4 g from 18.1 g in the control. Protein content was increased from 22.54% in the control to 23.98%. Mg content in seeds was up to 0.84% under this treatment as against 0.52% in the control.

CONCLUSIONS

Results show that melatonin at 100 µM, combined with magnesium at 28.57 kg ha⁻ produced the most favorable outcomes. This suggests a synergistic effect between melatonin and magnesium in enhancing the studied traits. These findings may also contribute to the future development of productive common bean breeding strategies.