APPLICATION OF RICE GENOMICS TO DEVELOP SUSTAINABLE CROPPING SYSTEMS FOR THE GULF COAST
Title: GENETIC DIVERSITY AMONG WEST AFRICAN RICE VARIETIES FOR GRAIN QUALITY TRAITS USING CHEMICAL AND DNA MARKER ANALYSES
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 1, 2003
Publication Date: June 1, 2004
Citation: Traore, K., Fjellstrom, R.G., McClung, A.M. 2004. Genetic diversity among West African rice varities for grain quality traits using chemical and DNA marker analyses. In: Rice Technical Working Group Meeting Proceedings, February 29-March 4, 2004, New Orleans, LA. 2004 CDROM.
Development of rice cultivars that are accepted by consumers requires evaluation of both objective and subjective quality factors. Because rice is generally consumed as a whole grain, physical properties, cooking quality, and sensory traits are very important. In some areas of West Africa, rice that has a short cooking time and slow digestibility is preferred by consumers. The objective of this study was to evaluate rice accessions from West Africa for genetic diversity in grain quality parameters and identify genetic resources for novel quality traits relative to U.S. germplasm. Thirty-nine rice varieties were introduced from the West Africa Rice Development Association (WARDA) located in the Ivory Coast. These included upland, rainfed, and irrigated cultivars as well as 'Nerica' varieties which are derived from interspecific crosses with Oryza glaberrima. DNA marker analyses were performed at the USDA-ARS Rice Research Unit in Beaumont, TX using leaf tissue from plants growing in a quarantine greenhouse and milled rice samples obtained directly from WARDA were analyzed for grain quality traits. The WARDA samples demonstrated a wide range for all quality parameters measured. They included grain shapes similar to long, medium, and short grain classes; aromatics and non-aromatics; red bran cultivars; chalky and translucent grains; etc. Using standard protocols, alkali spreading value (ASV), apparent amylase content, Rapid Visco Analyzer (RVA) pasting properties, Differential Scanning Calorimeter measurements, and cooking time were determined. DNA marker analysis was performed using random fingerprint markers as well as markers that are associated with the Waxy and alk loci, which are associated with amylose content and ASV, respectively.
The results showed that ASV varied from 4.0 to 7.0 and amylose content varied from 15.0% for Khao Dawk Mali 105 to 26.1% for CG14 which is an O. glaberrima cultivar. Cooking time varied from 11.7 minutes for Pusa Basmati to 24.0 minutes for WAB 56-104. Using the RM 190 marker which is associated with the Waxy gene, alleles common to those found in U.S. cultivars were identified as well as some rare alleles (103, 114, and 116). The three cultivars that had the 114 allele for RM190 were very similar in grain shape and all other quality measurements but ranged in cooking time by 4.9 minutes. The long grain cultivar Nerica 5 was unusual in that it possessed an amylose content and Waxy allele like Dixiebelle but had a weak RVA curve similar to L202. Jaya is a chalky medium grain cultivar that has the same amylose content and Waxy allele as Dixiebelle but a much stronger RVA curve. Bieu is a long grain cultivar with a short (15.5 minute) cooking time and a Waxy allele like Lemont, however it had a high amylose content and a strong RVA curve like Dixiebelle. The fingerprint marker data showed polymorphism among the varieties with markers RM210, RM214, RM224, RM234, RM247, and RM304 having 10 or more alleles among the 39 cultivars. The marker with the lowest amount of polymorphism was MRG6102 which is associated with the Pi-ta2 blast resistance gene in U.S. cultivars. Many crosses have been made between these WARDA lines and U.S. cultivars to develop mapping populations for further study.