Carbon isotope discrimination and yield of upland rice as affected by drought at flowering

• Published in: Pesquisa agropecuaria brasileira 2000-10, Vol.35 (10), p.1939-1947
• Main Authors: Pinheiro, B.S, Austin, R.B, Carmo, M.P. do, Hall, M.A
• Format: Article
• Language: English
• Subjects: AGRICULTURE, DAIRY & ANIMAL SCIENCE; AGRICULTURE, MULTIDISCIPLINARY; ARROZ DE SECANO; ARROZ SEQUEIRO; CARBON; CARBONE; CARBONO; CROP YIELD; DEFICIENCIA HIDRICA; DROUGHT RESISTANCE; DROUGHT STRESS; ESTRES DE SEQUIA; FLORACAO; FLORACION; FLORAISON; FLOWERING; internodes; ORYZA SATIVA; PRODUTIVIDADE; RENDEMENT DES CULTURES; RENDIMIENTO DE CULTIVOS; RESISTANCE A LA SECHERESSE; RESISTENCIA A LA SEQUIA; RESISTENCIA A SECA; RIZ PLUVIAL; spikelets fertility; STRESS DU A LA SECHERESSE; UPLAND RICE
• ISSN: 0100-204X; 1678-3921; 1678-3921; 0100-204X
• DOI: 10.1590/S0100-204X2000001000004

Field experiments involving upland rice genotypes, sown in various dates in late season, were carried out to assess the relationship of carbon isotope discrimination with grain yield and drought resistance. In each one of the three years, one trial was kept under good water availability, while other suffered water shortage for a period of 18-23 days, encompassing panicle emergence and flowering. Drought stress reduced carbon isotope discrimination measured on soluble sugars (deltas) extracted from stem uppermost internode at the end of the imposition period, but had relatively less effect on bulk dry matter of leaves, sampled at the same period, or that of uppermost internodes and grains, sampled at harvest. The drought-induced reduction in deltas was accompanied of reduced spikelet fertility and grain yield. In the three trials subjected to drought, genotypes with the highest yield and spikelet fertility had the lowest deltas. However, this relationship was weak and it was concluded that deltas is not a sufficiently reliable indicator of rice drought resistance to be useful as a screening test in breeding programs. On the other hand, grain yield and spikelet fertility of genotypes which were the soonest to reach 50% flowering within the drought imposition period, were the least adversely affected by drought. Then, timing of drought in relation to panicle emergence and to flowering appeared to be a more important cause of yield variation among genotypes than variation in deltas. Experimentos de campo, envolvendo genótipos de arroz de sequeiro, em várias datas de semeadura, realizadas tardiamente na estação de cultivo, foram conduzidos para investigar a relação da discriminação isotópica de carbono com a produtividade de grãos e resistência à seca. Em cada ano, um experimento foi mantido em boas condições hídricas, enquanto o outro sofreu falta de água, por período de 18-23 dias, abrangendo a emergência da panícula e florescimento. A deficiência hídrica reduziu a discriminação isotópica de carbono dos açúcares solúveis (deltas) extraídos do último entrenó do colmo, ao final do período de estresse, causando um efeito relativamente menor sobre a matéria seca das folhas amostradas na mesma ocasião, ou dos entrenós superiores e grãos amostrados na colheita. A redução de deltas induzida por deficiência hídrica foi acompanhada de redução da fertilidade das espiguetas e do rendimento dos grãos. Nos três experimentos submetidos a estresse hídrico, os genótipos de m