INTEGRATED MANAGEMENT OF INSECT PESTS IN STORED GRAIN AND IN PROCESSED GRAIN PRODUCTS
Location: Stored Product Insect Research Unit
Title: Methodology for assessing rice varieties for resistance to the lesser grain borer, Rhyzopertha dominica
Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 19, 2007
Publication Date: February 28, 2008
Citation: Chanbang, Y., Arthur, F.H., Wilde, G.E., Throne, J.E., Subramanyam, B.H. 2008. Methodology for assessing rice varieties for resistance to the lesser grain borer, Rhyzopertha dominica. Journal of Insect Science 8.16: 1-5.
Interpretive Summary: The lesser grain borer is an insect pest of stored rice throughout the world. One method for controlling lesser grain borers is through development of insect-resistant varieties of rice. In most cereal grains, kernel hardness is correlated with resistance to damage from the lesser grain borer; however, the hull of rough rice could offer some level of protection. We exposed young larvae of the lesser grain borer on different rice types with solid hulls, cracked hulls, and brown rice with the hull removed, and analyzed kernels for hardness and amylose content. More larvae penetrated the hull and developed to the adult stage on the kernel when the hulls were cracked, but neither the hardness of the rice kernel nor the amylose content of the kernel were correlated with development of the lesser grain borer larvae. This study shows that intact rice hulls are a barrier to lesser grain borer larvae, and that the characteristics of the kernel itself may not be as important in determining risk or susceptibility to this insect as the hull characteristics.
Single varieties of long-, medium-, and short-grain rough rice, (Oryza sativa L.), were analyzed for differences in percentage of broken hulls (splits and cracks in the husk), progeny production by Rhyzopertha dominica (F.), kernel hardness, amylose content of de-hulled brown rice, and neonate preferences for brown rice. The percentage of broken hulls was greater in long- and short-grain rice than medium-grain rice. Progeny production was lower in medium-grain rice than in long- or short-grain rice, and the number of adults in all three rice types was positively correlated with the percentage of broken hulls. Kernel hardness, amylose content, neonate preference for brown rice, and adult emergence from neonates introduced on the brown rice did not differ among rice types. Results of this test indicate that the soundness and integrity of the rice hull is a major factor in susceptibility to damage by R. dominica.