Heat stress effects around flowering on kernel set of temperate and tropical maize hybrids

RATTALINO EDREIRA, J.I.; BUDAKLI CARPICI, E.; SAMMARRO, D.; OTEGUI, M.E.

FIELD CROPS RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2011 vol. 123 p. 62 - 73

0378-4290

Final kernel number in the uppermost ear (KNE1) of most commercial maize (Zea mays L)crops is substantially smaller than the potential represented by the number of complete florets differentiated in this ear (NFE1), and than the number of silks exposed from it (NES1). Therefore, kernel set (KSE11= KNE1 NFE1-1; KSE12= KNE1 NES1-1) is usually <1, and is abstantially reduced when stressful conditions affect plant growth immediately before (GS1) or during (GS2) silking. In this work we evaluated mentioned traits in two field experiments (Exp1 and Exp2), including (i) two thermal regimes (TR), non-heated controls (TC) and plots heated (TH) during day-time hours (ca. 33-40 ºC 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, and silk exposure of individual plants. We computed the anthesis-silking interval (ASI), and three sources of kernel loss, identified as Loss 1 (decreased floret differentiation), Loss 2 (pollination failure), and Loss 3 (kernel abortion). Heating affected all surveyed traits, but (i) negative effects on flowering dynamics (reduced number of plants that reached the event and rate of development) were larger for anthesis than for silking with the concomitant decrease in ASI, and for GS1 than for GS2, (ii) caused a decrease in FPE1 only when performed during GS1 (-15.5% in Exp1 and -9.1% in Exp2), and only among Te and TeTr hybrids, (iii) promoted a reduction in NES1 of all GS × Hybrid combinations, and (iv) caused a steep decrease in KNE1 (mean of -51.8% in GS1 and -74.5% in GS2), KSE11 (mean of -28.5%), and KSE12 (mean of -38.6%). Kernel abortion (Loss 3) explained 95% of the variation in final KNE1 (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.