Edson A. Bastos1, Milton J. Cardoso1, Ricardo S. de Sousa2, Aderson S. de Andrade Júnior1, Valdenir Q. Ribeiro1, Ramilos Rodrigues de Brito3
Embrapa Mid -North, Av. Duque de Caxias, 5650, Teresina, Piauí State, ZIP 64006-220, Brazil 2 Post-Graduate Program in Agronomy, Federal University of Piaui(UFPI), Ininga Campus, Teresina, Piaui State, ZIP 64049-550, Brazil 3 Post-Graduate Program in Agronomy, State University of São Paulo (UNESP), Botucatu, São Paulo State, ZIP 18610-307, Brazil *Corresponding author. E-mail: firstname.lastname@example.org Abstract Maize has a great socio-economic importance in Brazil. However, there are many Brazilians regions that present irregular or low rainfall, reducingdrastically the grain yield due to water deficit. Therefore, it is essential to develop studies focused on the evaluation and identification of drought tolerant maize genotypes. Forty-two maize hybrids were evaluated in Teresina, Piauí State, northeastern Brazil, from September to December, 2010, under two irrigation water regimes: no water deficit (NWD) and water deficit (WD) during thereproductive phase, aiming identify genotypes tolerant to drought. The experimental design was randomized blocks with four replications. Irrigation was applied by conventional sprinkler system. Soil moisture content from 0.10 to 1.0 m was measured by Diviner 2000 probe. Grain yield and water use efficiency were evaluated. During the crop cycle irrigation depth plus rainwater were 692 mm and 491 mm for NWDand WD, respectively, implying in maximum soil water depletions of 26% (NWD) and 75% (WD). The water use efficiency was 11.7 kg.ha-1.mm-1 and 4.6 kg.ha-1.mm-1 for NWD and WD, respectively. Under water deficit, the average grain yield was 2,270 kg.ha-¹, i.e. 72 % lower than no water deficit regime (8,058 kg.ha-¹). Moreover, 18 hybrids produced above the average, especially the hybrids ALFA 10 (4,770kg.ha-¹), 30 A 37 (4,724 kg.ha-¹ ) and BX 1200 (4,562 kg.ha-¹ ). Key words: Zea mays L., water deficit, water use efficiency. 1. Introduction The maize (Zea mays L.) is one of the three most widely cultivated crops in the world. In the Brazilian Northeast is one of the most planted grain crops but with low productivity. Among the factors that impact this productivity, there is the water deficitcaused by the unevenness of the rainy season, where dry spells occur, often prolonged and at critical stages of growth and development of the crop. It is noteworthy that water scarcity is a growing problem in many parts of the world. Predictions of climate change such as increased mean air temperature and decreased rainfall indicate that water is becoming even scarcer. However, agriculture is themain water user, about 70% (Frenken & Kiersch, 2011), suggesting that its efficiency is necessary to preserve this limited resource. For Zwart and Bastiaanssen (2004), increased water use efficiency can be achieved by different approaches; one of these being the use of genotype capable of producing acceptable yields under water stress. Studies on drought tolerance involving maize can bringimprovements in growth and yield of crop grains in regions with limited water resources (Li et al., 2009). In Brazil, few studies have been developed to identify maize genotypes tolerant to water stress (Silva et
al., 2008, 2009, Teixeira et al., 2010, Cardoso et al., 2010; 2011a; 2011b; Brito et al., 2011, Bastos et al., 2008; 2011). Cardoso et al. (2011b), in order to identify maize cultivarswith drought and heat tolerance and more efficient water use observed mean values ranging from 1,157 kg.ha-1 to 7,946 kg.ha-1 for grain yield and 2.2 kg.ha-1.mm-1 at 14.9 kg.ha-1.mm-1 for water use efficiency under water deficit condition. There was average reduction in grains yield and water use efficiency by 53.6% and 38.6%, respectively. For Durães et al. (2004), providing tolerant genotypes to...