Grain quality variation and relationships with morpho-physiological traits in rice (Oryza sativa L.) genetic resources in Europe

Improvement of grain quality is the aim of all rice breeders, because it affects the commercial value of rice grains. The purpose of this research was to assess the variation in grain quality traits among rice (Oryza sativa L.) lines maintained in collections of five European rice-producing countries and to investigate possible relationships with morpho-physiological traits. A total of 318 lines were grown in the field. Milling, cooking, processing and nutritional qualities of grains, time to heading, time to maturity, plant height and panicle length were determined. There was considerable genetic variation among lines for all traits examined. Brown rice grain length (GL) ranged from 4.3 to 8.5 mm, grain width (GW) from 1.9 to 3.6 mm and grain length-to-width ratio (L/W) from 1.3 to 4.0. GL was negatively correlated with GW, indicating that selection for long grains would result in a negative response of GW. Grain pearl (GP) ranged between I and 100%, and was negatively correlated with GL and grain L/W. Total milling yield (TMY) and whole grain yield (WGY) ranged from 53.8 to 76% and from 7.8 to 69.8%, respectively. Differences in TMY and WGY among lines were associated with line maturity. Both milling yield parameters were higher for early maturing lines than for late maturing lines. Amylose content (AC) ranged from 12.8 to 27.6% while grain protein content (PC) ranged from 4.8 to 11.9%. PC was greater in tall and late maturing lines than in short and early maturing ones. Gelatinization temperature ranged from 50.1 to 77.5 degreesC with a mean value of 61.56 degreesC. The variation among lines found in this study offers opportunities to breed for grain quality in either direction in order to meet the specific requirements of each country. By the material examined, 25 lines met all the requirements of Indica type rice. These lines could be used as parents for introducing desired traits to current Indica cultivars grown in Europe. Additionally, the interrelations among grain quality traits found in this study may be useful to understand the relationship among grain quality components and to optimize the selection criteria. (C) 2003 Elsevier B.V. All rights reserved.