Heat stress in temperate and tropical maize hybrids: Kernel weight determination

RATTALINO EDREIRA, J.I.; OTEGUI, M.E.

Bento Gonçalves, Rio Grande do Sul

Congreso; VI International Crop Science Congress; 2012

International Crop Science Society

Heat stress affects kernel growth as it influences both rate and duration of grain filling. The former has been linked with potential kernel weight and may be affected by heating around flowering. The latter depends on assimilate availability per kernel during effective grain filling (i.e. postflowering source-sink ratio), and may be affected by heating during this period. The magnitude of these effects has not been documented for heat stress. In this work we evaluated mentioned traits in ?eld experiments (Exp1 and Exp2), including (i) two temperature regimes, control and heated during daytime hours (ca. 33-40 °C at ear level), (ii) three 15-d periods (GS1: presilking; GS2: from silking onwards: GS3: active grain filling), and (iii) three hybrids (Te: temperate; Tr: tropical; TeTr: Te×Tr) with contrasting tolerance to heat stress. We also assessed the dynamic of water-soluble carbohydrates (WSC) in stem. Heat stress reduced final kernel weight (KW) in most of heated plots, but the magnitude of this effect was larger for (i) the Te (-20%) hybrid than the TeTr (-11%) and Tr (-9%) hybrids, and (ii) GS3 (-22%) than GS1 (-6%) and GS2 (-11%). Negative effect of heating on final KW was mostly related to changes in the duration of grain filling (r2= 0.49; P