Identification and Characterization of Phosphorus Deficiency Tolerant Rice Genotypes in North-Eastern India

An essential element for healthy plant growth and development is phosphorus (P). Globally, lack of phosphorus (P) is a major factor affecting rice productivity. P insufficiency issues generally occur in iron-toxicity soils, soils with aluminium or manganese content, and acidic soils which accounts for over 80% of the area of land in North Eastern India. Also, 60-80% P of rice plants is deposited and stored in the form of phytate which also chelates the availability of Zn and Fe making them unavailable to human and monogastric animals and subsequently environmental pollution and eutrophication. To address the challenges to food and nutrition security, it is crucial to identify high P absorption ability from soil simultaneously reduced P in rice grains using available untapped plant genetic resources. In the present investigation, 96 rice germplasm were screened for phosphorous tolerance using Pup1 gene-based markers. Based on two markers (K46 and K20), only 15 genotypes (15.63%) were positive for PUP1 gene. Hydroponic treatment with low phosphorus revealed Mata Maha and Chakhao Lamhing as the most tolerant genotypes to P deficiency. The correlation analysis found that grained P content was significantly and positively correlated with grain Iron (0.551) and grain Zinc content with grain Fe (0.480). The range of grain P content was 0.27 mg/g (Insatang Makokching) - 3.78 mg/g (Allechisho) with an average of 1.81mg/g. Intriguingly, the PUP1 gene is also significantly associated with P content in grain by enhancing the P content which is an undesirable trait. However, Insatang Makokching rice genotype showed the least P content (0.27mg/g) in grain though the presence of the positive PUP1 gene. A single nucleotide substitution (G/C) in the eight-exon position of SPDT gene altering the amino acid glycine (G) to arginine (R) in Insatang Makokching rice genotype could be the reason for lowering P content via altering the function of the SPDT protein in node I of panicles. Therefore, convergent selection of PSTOL1 and SPDT genes in rice for low phosphorus tolerance and reduced P grain content would be advantageous but require further validation.