Influence of high temperature during pre- and post-anthesis stages of floral development on fruit-set and pollen germination in peanut

Peanut (Arachis hypogaea L.) crops are often exposed to day temperatures > 35 degreesC for short periods during flowering, resulting in lower yields. Research was conducted to study and quantify the effects of short episodes (1-6 d) of high temperatures during the pre- and post-anthesis stages of floral development on fruit-set, pollen viability, germination and tube growth. Plants of peanut cv. ICGV-86015 were grown in controlled environments at 28/22 degreesC (day/night). High daytime air temperature treatments ranging from 28 (control) to 48 degreesC were imposed at different times between 6 d before anthesis (DBA) and 6 d after anthesis (DAA) for 1, 3 or 6 d. Floral buds or flowers were tagged at different stages to determine fruit-set. Exposure to bud (tissue) temperature greater than or equal to 39 degreesC for 1 d significantly reduced fruit-set compared to the control at 28 degreesC, and the magnitude of the reduction varied with stage of floral development. Floral buds were most sensitive to high temperature at 4 DBA and at anthesis, coinciding with micro-sporogenesis and pollination or fertilisation, respectively. The critical bud temperature at these stages was 33 degreesC, above which fruit-set was reduced by 6% degreesC(-1). Lower fruit-set due to high temperatures at pre-anthesis and anthesis stages were due to pollen sterility and retarded pollen tube growth, respectively.