Effects of Different Sowing Dates on Photosynthetic Pigments and Stress-Related Biochemical Traits in Common Bean (Phaseolus vulgaris L.)

The present study investigated the effects of different sowing dates on photosynthetic pigments and stress-related biochemical characteristics in the leaves of seven common bean (Phaseolus vulgaris L.) genotypes under the ecological conditions of Bayburt, Türkiye. Field experiments were conducted during the 2019 growing season using a randomized complete block design with three replications. Three sowing dates (7 May, 22 May, and 6 June) and seven bean genotypes were evaluated. Chlorophyll a, chlorophyll b, carotenoid, proline, malondialdehyde (MDA), and total phenolic compound contents were determined using standard spectrophotometric methods. Sowing date significantly affected chlorophyll a and carotenoid contents, whereas chlorophyll b, proline, malondialdehyde, and total phenolic compound contents were not significantly affected. The second sowing date (22 May) resulted in the highest mean chlorophyll a and chlorophyll b contents, although the effect on chlorophyll b was not statistically significant, whereas the highest carotenoid content was recorded in the earliest sowing date (7 May). Genotypic differences in the investigated biochemical traits were generally not statistically significant. These findings indicate that sowing date primarily affected selected photosynthetic pigments, particularly chlorophyll a and carotenoids, while the evaluated sowing dates did not significantly alter the measured stress-related biochemical parameters under the environmental conditions of Bayburt.