ABSTRACT
Physiological, biochemical and morphological responses of diverse tomato genotypes to early drought stress

Shormin Choudhury1, Sarwar Hossain1, Nazrul Islam1, Rezwan Sarker1, Md Arif Hussain2, Fatmah A. Safhi3*, Areej S. Jalal3, Nora M. Al Aboud4, Mohammed O. Alshaharni5, and Md Sazzad Hossain6*
 
Drought stress is a major environmental constraint that significantly affects tomato (Solanum lycopersicum L.) productivity, particularly during early stages of plant development. This study evaluated the physiological, biochemical, and morphological responses of 19 tomato genotypes under early drought stress to identify drought-tolerant cultivars. Seedlings were subjected to drought stress by withholding irrigation for 14 d at 35 d after sowing. Across genotypes, drought caused significant reductions in chlorophyll a by 28%-46%, chlorophyll b by 25%-41%, relative water content (RWC) by 22%-39%, shoot biomass by 30%-55%, and root biomass by 27%-49% compared to non-stressed control plants. Conversely, reducing sugars and phenolic content increased by up to 32% and 47%, respectively, reflecting osmotic adjustment and antioxidant activation. Significant genotypic variation was observed; tolerant cultivars such as BARI-F1-5, BARI-15, BARI-11, and Pathorkuch maintained higher RWC (> 60%), chlorophyll levels more effectively (≥ 70% of control), and stronger root-shoot development (root length up to 24 cm, shoot dry weight up to 1.5 g). In contrast, sensitive genotypes including ‘Roma-VF’, ‘BARI-2’, and ‘BARI-21’ showed significant reductions with chlorophyll content declining below 50% of non-stressed control and RWC reducing to 45%. Multivariate analyses (hierarchical clustering, heatmap, principal component analysis) grouped the genotypes into tolerant, intermediate, and highly sensitive classes. The results indicate that integrating physiological (chlorophyll, RWC), biochemical (sugars, phenols), and morphological (root-shoot growth) parameters provides an effective strategy for screening drought-tolerant tomato germplasm. The identified tolerant genotypes represent valuable genetic resources for breeding programs aimed to enhance tomato resilience in water-limited environments.
Keywords: Early-stage drought screening, genotypic variation, osmotic adjustment, phenolic compounds, photosynthetic pigments, physiological response to drought, shoot and root biomass, Solanum lycopersicum, tomato physiology.
1Sher-e-Bangla Agricultural University, Department of Horticulture, Dhaka, Bangladesh.
2Sher-e-Bangla Agricultural University, Department of Biochemistry and Molecular Biology, Dhaka, Bangladesh.
3Princess Nourah bint Abdulrahman University, College of Science, Department of Biology, Riyadh 11671, Saudi Arabia.
4Umm Al-Qura University, Faculty of Science, Department of Biology, Makkah 24372, Saudi Arabia.
5King Khalid University, College of Science, Biology Department, Abha 61321, Saudi Arabia.
6Sylhet Agricultural University, Department of Agronomy and Haor Agriculture, Sylhet, Bangladesh.
*Corresponding author (faalsafhi@pnu.edu.sa, sazzadmh.aha@sau.ac.bd)