Genotypic differences in morphological, physiological and agronomic traits in response to drought in tobacco genotypes

The detrimental effects of drought stress on the growth, productivity, and quality of tobacco (Nicotiana tabacum L.) underscore the necessity of identifying drought-tolerant germplasm for breeding programs. This study evaluated the drought tolerance of 295 tobacco genotypes, primarily from East Asia and North America. A preliminary screening involved withholding water until soil moisture reached 6%, followed by assessment of various morphological and physiological traits from which an integrated score was calculated. Considerable genetic diversity was found among the genotypes with respect to drought tolerance, leading to the identification of 16 tolerant and 6 sensitive genotypes. The drought tolerance of these 22 genotypes were validated in a subsequent pot experiment, confirming the preliminary screen. Most drought-tolerant genotypes were Chinese landraces, with T218 (An Shun Da Diao Zhi Bian Zhong) identified as the most tolerant and T180 (Long She Yan) as the most sensitive; both are Chinese landraces. Further analysis showed that under well-watered conditions, T218 and T180 had similar agronomic traits, with T180 had slightly superior photosynthetic performance at the seedlings stage. Under drought stress, T218 exhibited less growth inhibition, higher antioxidant enzyme activities, greater glutathione (GSH) accumulation, and lower malondialdehyde (MDA) levels compared to T180. The findings of this study have identified valuable germplasm for the genetic improvement of drought tolerance in tobacco and material that will facilitate a better understanding of the effects of drought on the regulation of metabolism, physiology, and biochemistry.