Survey of Rice Genotypes of Southern India for Seed Zinc Concentration to Explore its Seed Endophytic Microbial Diversity

Background: Rice is a vital staple food for a large part of the global population and zinc deficiency poses health risks, particularly in rice-dependent regions. Studying genotypic differences in rice seed zinc content is vital for breeding zinc enriched varieties to address malnutrition and enhance food security. In the plant microbe partnership exploring the role of seed bacterial endophytes in influencing the plant physiology holds promise for Zn accumulation contributing to the broader goals of enhancing food quality, nutrition and crop production in a world facing increasing agricultural demands and challenges. Methods: Rice genotypes were surveyed and their seed zinc content was analysed using non-destructive X-ray fluorescence spectrometry. Surface sterilization of rice seed samples was performed to isolate endophytic bacteria, involving a series of treatments with distilled water, ethanol and sodium hypochlorite to remove surface microflora. The sterilized seeds were then macerated and diluted to obtain a countable number of colonies, which were subsequently spread-plated on nutrient agar, tryptic soy agar and soil extract agar to enumerate the different nutritional types of seed endophytic microflora. Result: In this study, 34 different rice genotypes, comprising traditional landraces and modern cultivars, were collected and analysed for their inherent zinc content. One variety in each category of low, medium and high seed Zn content was selected. The occurrence of all nutritional types of bacterial and their population was highest in the genotype Karuppunel followed by CO51 and ADT 39. Nutrient agar was found to promote a higher count of culturable bacterial endophytes compared to Tryptic soy agar and Soil extract agar.