Comparing Hydroponics, Sand, and Soil Medium To Evaluate Contrasting Rice Nagina 22 Mutants for Tolerance to Phosphorus Deficiency

Abstract

Soils deficient in P are widespread in major rice (Oryza sativa L.) ecosystems. In view of declining reserves of rock phosphate and the rising costs of P fertilizers, breeding rice varieties tolerant to low P has become important for future food security. Four different methods (hydroponics without sand [H], hydroponics with sand [HS], large pots with soil [PS], and glasses with soil [GS]) were evaluated using rice aus variety Nagina 22 (N22) and its known gain‐of‐function (gof) and loss‐of‐function (lof) mutants to screen for low P tolerance in the field. In −P (no addition of NaH2PO4) shoots, dry weight was significantly higher in gof mutant NH787 than in N22 in HS, PS, and GS but not in H, with fold increases of 1.8 in HS, 5.2 in GS, and 9.4 in PS. In HS, in −P, out of six traits only shoot dry weight was significantly higher in gof and lower in lof mutants. However, in GS both root and shoot dry weight could confirm gof and lof mutants. It took 40 d in GS and 70 d in PS to differentiate between growth in –P/low P and +P (0.32 mM NaH2PO4) and between gof and lof mutants. Thus, shoot dry weight at 30 d in HS and root and shoot dry weight at 40 d in GS are best to differentiate between genotypes grown in –P/low P and +P soil and also between gof and lof mutants for low P tolerance. The HS method can be performed in ambient conditions and needs 70% less medium compared with H. If germplasm is to be screened for low P tolerance on a large scale and if there is no access to low‐P soil, then screening using HS is the best approach.