Micro-fibre pollination bags and high viability Pinus patula pollen enhance cone survival and seed set during controlled pollination

Abstract

The influence of four types of isolation material and pollen viability on cone survival and seed set during controlled pollination of Pinus patula Scheide et Deppe was investigated. Very low cone-survival figures for controlled pollination of P. patula are reported by the forestry industry in South Africa. The reported studies were conducted over two pollination seasons in 1997 and 1998 and the effect of treatments was monitored during the cone development period (22 months) and was extended to a cone-analysis study after harvest. Cone-survival 20 months after pollination varied between 36% and 46% for micro-fibre isolation material compared to 19% to 32% for polythene. Developed seed yields also improved when micro-fibre material was used, with white micro-fibre (98) yielding best results compared to green micro-fibre (64), polythene (67) and sponge (56). Relative humidity (RH) inside the microfibre bags was up to 20% below ambient during daytime hours, while the polythene and sponge treatments maintained increased levels of relative humidity, 40-50% higher than ambient. All bag types displayed increased temperatures over ambient, with the sponge treatment reaching temperatures as much as 10°C higher than ambient. The use of high viability pollen increased cone survival at harvest by 23% and mean number of developed seeds by 21 seeds per cone. The type of isolation material used during controlled pollination has a major impact on cone survival and seed set, while the role of pollen viability and self-pollination in successful controlled pollination was demonstrated.