Dry matter and N accumulation and translocation for Indica and Japonica rice under Mediterranean conditions

Part of the dry matter and N accumulated by rice (Oryza sativa L.) plants until anthesis is translocated to grain during the grain filling period. A field study was conducted to assess the dry matter and N accumulation and translocation of direct water-seeded rice and examine their association with grain yield. Five rice cultivars, Olympiada and L-202 (Indica type) and Ispaniki A', Melas and Dion (Japonica type), with contrasting characteristics were grown in a silty loam soil (Aquic Xerofluvents) in 1999 and 2000. Cultivar dry matter translocation efficiencies ranged from 8.5 to 39.3% and N translocation efficiencies from 44.7 to 66.7%. Differences among Indica and Japonica cultivars in translocation efficiencies were found, but these differences depended mainly on the agronomic characteristics of each cultivar. Dry matter and N translocation were greater for short and late maturing cultivars compared to the tall and early maturing or mid-season cultivars, respectively. Greater amounts of dry matter and N content at anthesis resulted in a greater dry matter and N translocation to grain. Grain yield was positively and significantly correlated with dry matter and N translocation efficiency, suggesting that the sink strength could be involved in the translocation efficiency. The contribution of pre-anthesis accumulated reserves to grain weight ranged from 9.1 to 42.2%, indicating the importance of pre-anthesis storage of assimilates for attaining high grain yield of rice under Mediterranean conditions. (C) 2002 Elsevier Science B.V. All rights reserved.