Studies on tillering ability of rice under phosphorus stress

Abstract

A series of experiments were conducted in solution culture in the greenhouse, growth chamber, controlled environment room, and in the field on P-deficient rice soil at the Texas A&M University Agricultural Research and Extension Center near Beaumont. The objectives were the following: (1) develop screening techniques to identify tillering ability under P stress, (2) evaluate tiller development, grain yield and yield components of rice under P deficient and sufficient conditions, and (3) determine the heritability of tiller and panicle development under P stress. Screening rice for tolerance to P-deficiency, as exhibited by tillering ability, was best when plants were grown in a P-deficient nutrient solution in the greenhouse during the normal growing season. Studies indicated that higher tillering type cultivars could partially compensate for a mild P-deficient condition. Results also indicated that tiller production of each cultivar was markedly affected by the climate and the P level in the culture solution. Field experiments in P-deficient Beaumont clay soil (5 ppm P as determined by 1.0 M NH4OAc-1.4 M HCl-0.01 M EDTA, pH 4.2) were conducted in 1982 and 1983. The design included two P levels, 0 and 45 kgP2O5/ha, with 19 cultivars in 1982 and 12 cultivars in 1983. Phosphorus application promoted tiller development and increased plant height, panicle weight, and grain yield. The plants receiving P exhibited earlier first tillering, heading, and maturity dates. The grain yield increase in the plots receiving P was due to the increase in panicle number. Grain number per panicle, filled grain percentage, and thousand filled grain weight were not statistically increased at the .05 probability level by the application of P. The high environmental effect may have masked the occurrence of cultivar x P level interactions. Cultivars were classified as tolerant to low levels of soil P if their grain yield performance was similar whether grown under low or adequate soil P conditions. Eight crosses between P-deficiency tolerant, and susceptible cultivars were evaluated for tillering response to soil P levels. Parents and F2's were grown under conditions of adequate and low P. The influence of environment on the cultivars appeared to be greater than the influence of genetic factors for the cultivars and environmental conditions used in these tests.