PLANT GROWTH PROMOTING PSEUDOMONAS ENHANCES SALINITY TOLERANCE IN CARROT (DAUCUS CAROTA L.) THROUGH MORPHOLOGICAL AND BIOCHEMICAL MODULATION ACROSS DIVERSE GENOTYPES

Abstract

Salinity is a key abiotic restriction on carrot (Daucus carota L.) productivity worldwide. Plant growth-promoting rhizobacteria (PGPR) are an environmentally friendly way to improve crop tolerance to salinity. This study examined the morphological and biochemical responses of 30 carrot genotypes to control (T₀), salt stress (T₁), and salt stress combined with Pseudomonas bioinoculation (T₂). The experiment was conducted using a randomized complete block design with three replications. Morphological features such as root length, root weight, and root diameter were assessed, as well as biochemical measures such as total soluble sugars (TSS), reducing sugars (RS), phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD). Salinity significantly (P < 0.001) decreased root growth, PAL, PPO, and decreasing sugar levels, but raised TSS and POD activities, indicating osmotic correction and activation of antioxidant defence systems. Bioinoculation with Pseudomonas partially restored root growth and antioxidant enzyme activities while reducing oxidative stress under saline conditions. Significant genotype-treatment interactions were found for morphological features and PPO activity, indicating genetic heterogeneity in salinity tolerance. Pearson correlation study found a substantial positive relationship between root weight and diameter (r = 0.942). PCA explained 51.85% of total variation, with root morphological features playing the most important role in genotype discrimination, while hierarchical cluster analysis classified the examined genotypes as salt-tolerant or salt-sensitive. Genotypes 9, 11, 21, 26, 28, and 30 consistently showed superior growth in saline circumstances, indicating that they could be useful genetic resources for breeding salt-tolerant carrot cultivars. These data show that Pseudomonas bioinoculation efficiently reduces salinity-induced damage and offers a potential technique for long-term carrot production in salt-affected soils.