Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/8/2002
Publication Date: 6/1/2002
Citation: THOMAS, A., PINSON, S.R., OSBORN, G.S. DETERMINING THE EFFECT OF MOISTURE DIFFUSIVITY ON FISSURE RESISTANCE OF FOUR RICE VARIETIES. RICE TECHNICAL WORKING GROUP MEETING PROCEEDINGS. 2002. p. 119.
Technical Abstract: Kernel fissuring is one of the leading causes of reduced milling yield. Any reduction in fissuring will result in direct increases in yield and profit for the producer and miller. A clearer understanding of the contributions of each physiological component of the paddy rice seed toward the overall mechanism of fissuring is needed to identify the physical, chemical and genetic components responsible for fissure resistance in rice grains. Grain fissuring is triggered by readsorption of moisture into drying kernels. The rate at which the moisture enters and moves through the rice grain (a.k.a. diffusivity) likely plays a major role in fissure response. The objective of this study is to clarify how differential diffusivity determines fissure response. Four varieties ranging from high to low fissure resistance were selected for this study; Cypress, Lemont, LaGrue, and Teqing. Moisture diffusivity of the hull, bran, and endosperm was calculated by determining the diffusivity of water through white rice, brown rice, and paddy rice. Hull diffusivity accounted for the difference in diffusivity between paddy and brown rice and bran diffusivity accounted for the difference in diffusivity between brown and white rice. We first modified and optimized a laboratory method for determining fissure resistance so that differences between paddy and brown rice and the four rice varieties were detectable at a 0.5 significance level. Cypress shows the most fissure resistance, Teqing the least, with Lemont and LaGrue having intermediate resistance. We find a clear correlation between fissure resistance and diffusivity of paddy rice. We are still investigating association between fissure resistance and diffusivity of individual grain components i.e. hull, bran and endosperm.