A Study of methods of varietal identification and mechanical separation in selected varieties of rice (Oryza sativa L.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University, New Zealand

Abstract

Varietal identification and mechanical separation methods were studied using 10 rice varieties (C12, C22, C168, C4-63G, C4-137, BPI-Ri4, IR36, IR40, IR42 and IR44) obtained from the Philippines. Three sets of characters were considered; seed and plant morphological characters as well as a biochemical character. The seed morphological characters assessed were the 1000 grain weight, length, width and thickness. Enlarged photographs were taken of whole seed and photographs of the seed surface were also taken with the use of the scanning electron microscope at 40x and 240x magnifications. Morphological differences were observed between the varieties except in closely related ones and where the dimension distribution overlapped. Enlarged photographs were valuable aids for the observation of macroscopic characters. There are possibilities of differentiating varieties through the micromorphological characters of their seed coats. Plant morphological characters were observed during the entire period of growth. The more discernible ones were coleoptile colour, date of heading, plant height, leaf length, leaf width and tillering capacity. Extreme variability was observed as the plants were affected by environmental factors. Electrophoresis of the glutelin fraction of rice protein was conducted on polyacrylamide gel. No significant differences were observed in the mobility as well as relative intensity of the protein bands. An attempt was made to separate 45 mixtures of the different varieties in five laboratory models of processing machines (Bardex Ql, Specific Gravity Separator, Indented Cylinder Separator, Air-Screen Cleaner and Seed Blower). Promising separation results were obtained with all the machines but for practical purposes, three machines; Bardex Ql, Indented Cylinder Separator and Air-Screen Cleaner proved most useful.