Comparing hydroponics, sand and soil medium to evaluate contrasting rice N22 mutants for tolerance to phosphorus deficiency

Abstract

Soils deficient in P are widespread in major rice ecosystems. In view of declining reserves of rock phosphate and rising costs of P-fertilizers, breeding rice varieties tolerant to low P becomes important for future food security. Four different methods 1. Hydroponics without sand (H), 2. Hydroponics with sand (HS), 3. Large pots with soil (PS) and 4. Glasses with soil (GS) were evaluated using rice aus variety Nagina 22 (N22) and its known gain/loss of function (gof/lof) mutants to screen for low P-tolerance in field. In –P shoot dry weight was significantly more in gof mutant NH787 than in N22 in HS, PS and GS but not in H with fold increase of 1.8 in HS, 5.2 in GS and 9.4 in PS. In HS, in -P, out of 6 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 40d in GS and 70d in PS to differentiate between growth in –P/ low P and +P and also between gof and lof mutants. Thus shoot dry weight at 30d in HS and both root and shoot dry weight at 40d in GS are best to differentiate between genotypes grown in –P/lowP and +P and also between gof and lof mutants for low P tolerance. The HS method can be carried out in ambient conditions and needs 70% lesser medium compared to H. If germplasm is to be screened for low P tolerance on a large scale, and there is no access to low P soil, then screening using HS is best.