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Using a Moisture Transport Model for Identifying the Genes Expressing Field Fissure Resistance in Rice Seed

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  036193,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.15423)
Authors:   Audrey T. Waggoner, G. Scott Osborn, Shannon R. Pinson
Keywords:   Moisture diffusivity, fissure, rice, moisture transport model, genetics

Field rice fissuring is one of the leading factors in reduction of whole head rice yield. Through research and careful design, engineers have made great progress over the past several decades in preventing reduction of head rice yield caused by harvesting and processing operations. However, one of the leading factors in reduction of head rice yield is infield fissuring, which cannot be prevented through equipment design since it occurs prior to harvest. In-field fissuring occurs mainly from re-adsorption of ambient moisture from rain or high humidity into the endosperm as the seed dries during maturation, but before full harvest maturity is attained. The fissures cause breakage during milling resulting in reduce whole kernel yield. Weather cannot be controlled and the most likely control point for reducing field fissuring is at the genetic level as different varieties of rice have been observed to resist in-field fissuring better than other varieties. The objective of this project was to develop a tool to identify if a genetic line in development is resistant to field fissuring and determine the physiological mechanism within the seed mainly responsible for conveying this resistance. By identifying the physiological component of fissure resistance, the search space for the responsible genes within the genome can be reduced. This work examined 4 representative varieties of rice with know field fissure resistance: ‘Cypress’ (high resistance); ‘Lemont’ (medium); ‘LaGrue’ (medium); and’ Teqing’ (low). Tests were conducted to compare the moisture transport properties between these varieties by determining moisture adsorption and desorption rates for white, brown and paddy rice. A three dimensional finite difference model was written to account for moisture transfer within paddy, brown, and white seed. Diffusivity values were determined for seed components. These values were used in the model to determine the magnitude, location and elapsed time of moisture gradient formation within the endosperm to compare varieties under ambient drying and rewetting conditions. The magnitude of the gradients directly corresponded with observation of field fissuring. The source of fissure resistance was not the same for each variety as hull and bran layer moisture resistance was important, but high endosperm diffusivity also appeared to play a significant role.