Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/1998
Publication Date: N/A
Citation: Romeis, J., Shanower, T.G., Peter, A.J. 1999. Trichomes on Pigeonpea [Cajanus cajan (L.) Millsp.] and Two Wild Cajanus spp.. Crop Science. 39(2): 574-578 DOI:10.2135/cropsci1999.0011183X003900020045x. Interpretive Summary: Pigeonpea is an important grain legume in south Asia and the semi-arid regions of Africa and Latin America. Many species of insects attack the cro though the pod borer is the most damaging and difficult to control. Considerable effort has been devoted to identifying less susceptible pigeonpea genotypes, but with only limited success. Recent research has indicated that wild relatives of pigeonpea may possess insect resistance mechanisms not found in pigeonpea. One of these mechanisms is a dense layer of hairs which cover the pods of a related wild species. This study was conducted to identify and characterize the distribution of trichomes on pigeonpea and two wild species. Five trichome types were identified. The density of the different types varied substantially among plant parts, amon species, and between field-grown and greenhouse-grown plants. Cajanus scarabaeoides had the highest density of nonglandular trichomes and it may be possible to transfer this trait to cultivated pigeonpea to reduce damag due to insects.
Technical Abstract: Trichomes have been modified in a number of crops to develop insect-toleran genotypes. Pigeonpea, Cajanus cajan (I.) Millsp., is often heavily damaged by insect pests, and trichomes provide a potential insect resistance mechanism. The following study was conducted to identify and characterize the distribution of trichomes on pigeonpea and two wild species, C. platycarpus (Bentham) can der Maesen and C. scarabaeoides (L.) Thours. Three glandular (Type A, B, and E) and two nonglandular (Types C and D) trichome types were identified with light and electron microscopy. Types A B, C, and D were found on leaves, pods, and calyxes of all three Cajanus spp., except for Type A, which was not found on pods and calyxes of most C. scarabaeoides accessions examined. Because of their small size and rarity, Type E trichomes were not considered tin this study. Pods of C. cajan and C. platycarpus. Trichome density on pods varied significantly among pigeonpea genotypes and different accessions of C. Scarabaeoides. Differences across seasons and in greenhouse versus field-grown plants were also significant. Leaves of C. platycarpus possessed the fewest trichomes, while C. cajan and C. scarabaeoides had highly pubescent leaves. The resistance of C. scarabaeoides pods to Helicoverpa armigera (Hubner) larvae reported in an earlier study is due to the high density of nonglandular trichomes. This wild species may thus be an important source for developin insect resistant pigeonpea.