Deciphering Seedling-Stage Salinity Stress Tolerance in Maize Genotypes Through Morpho-Physiological and Ionic Traits

Area of Science:

• Agricultural Science
• Plant Physiology
• Genetics

Background:

• Salinity stress significantly impacts maize (Zea mays L.) growth and development, especially during the critical seedling stage.
• Key detrimental effects include osmotic stress, chlorophyll degradation, and disruption of ionic homeostasis, leading to reduced biomass and yield potential.
• Understanding genotypic variations in response to salinity is crucial for developing salt-tolerant maize varieties.

Purpose of the Study:

• To investigate the morpho-physiological and ionic responses of diverse maize genotypes under varying salinity levels.
• To identify key physiological traits and genetic markers associated with salinity tolerance in maize seedlings.
• To elucidate the adaptive mechanisms employed by maize to cope with salt stress.

Main Methods:

• Maize seedlings were subjected to controlled salinity treatments (0, 3, 6, and 9 dS/m).
• Morphological parameters (biomass, plant height) and physiological indicators (photosynthetic pigments, K+/Na+ ratio) were measured.
• Statistical analyses, including stress tolerance indices and principal component analysis (PCA), were employed to evaluate genotypic differences and trait correlations.

Main Results:

• Increasing salinity levels significantly reduced plant height, shoot fresh weight, and shoot dry weight across genotypes.
• Genotypic variability was observed in photosynthetic pigment content (chlorophylls and carotenoids) and the K+/Na+ ratio.
• Chlorophyll stability, carotenoid accumulation, and maintaining a high K+/Na+ ratio were identified as critical determinants of salinity tolerance.
• Principal component analysis indicated a shift from biomass-driven variation to pigment- and ion-driven variation under high salinity stress.

Conclusions:

• Maize genotypes exhibit distinct physiological and ionic regulation strategies in response to salinity stress.
• Genotypes BML 6 and HKI 163 demonstrated superior salinity tolerance, characterized by higher pigment content and better K+/Na+ balance.
• These findings highlight crucial traits for early-stage salinity tolerance and provide a basis for breeding salt-resistant maize cultivars.