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Heat stress effects around flowering on kernel set of temperate and tropical maize hybrids |
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| Authors: | JI Rattalino Edreira E Budakli Carpici D SammarroME Otegui |
| Institution: | a Instituto de Fisiología y Ecología Vinculado a la Agricultura del Consejo Nacional de Investigaciones Científicas y Tecnológicas (IFEVA-CONICET), Facultad de Agronomía Universidad de Buenos Aires (FAUBA), Av. San Martín 4453, Buenos Aires, Argentina b Departamento de Producción Vegetal, FAUBA c Department of Field Crops, Faculty of Agriculture, Uludag University, 16059 Bursa, Turkey |
| Abstract: | Final kernel number in the uppermost ear of temperate maize (Zea mays L.) hybrids is smaller than the potential represented by the number of florets differentiated in this ear, and than the number of silks exposed from it (i.e., kernel set <1). This trend increases when stressful conditions affect plant growth immediately before (GS1) or during (GS2) silking, but the magnitude of change has not been documented for heat stress effects and hybrids of tropical background. In this work we evaluated mentioned traits in field experiments (Exp1 and Exp2), including (i) two temperature regimes, control and heated during daytime hours (ca. 33-40 °C at ear level), (ii) two 15-d periods during GS1 and GS2, and (iii) three hybrids (Te: temperate; Tr: tropical; TeTr: Te × Tr). We also measured crop anthesis and silking dynamics, silk exposure of individual plants, and the anthesis-silking interval (ASI). Three sources of kernel loss were identified: decreased floret differentiation, pollination failure, and kernel abortion. Heating affected all surveyed traits, but negative effects on flowering dynamics were larger (i) for anthesis than for silking with the concomitant decrease in ASI, and (ii) for GS1 than for GS2. Heat also caused a decrease in the number of (i) florets only when performed during GS1 (−15.5% in Exp1 and −9.1% in Exp2), and only among Te and TeTr hybrids, (ii) exposed silks of all GS × Hybrid combinations, and (iii) harvestable kernels (mean of −51.8% in GS1 and −74.5% in GS2). Kernel abortion explained 95% of the variation in final kernel numbers (P < 0.001), and negative heat effects were larger on this loss (38.6%) than on other losses (≤11.3%). The tropical genetic background conferred an enhanced capacity for enduring most negative effects of heating. |
| Keywords: | ASI anthesis-silking interval CST cumulative stressful temperatures E1 apical ear Expn experiment n GSn growth stage n H hybrid KNE kernel number per E1 KSE1 kernel set per developed floret in E1 KSE2 kernel set per exposed silk in E1 NES number of exposed silks from E1 FPE florets number per E1 Pop proportion of the population of plants TC non-heated control plot Te temperate hybrid TeTr temperate per tropical hybrid TH heated plot Tmax maximum temperature Tr tropical hybrid TR temperature regime |
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