Variability of initial and final nut set in elite macadamia selections using different pollination methods

Abstract

Selection for yield in macadamia is a major component of the Australian industry breeding program because of its high economic weighting. Pollination success initially determines the nut set and consequently the yield of a tree. The method of pollination may affect the initial nut set (INS) and final nut set (FNS). Tested genotypes are currently involved in a regional cultivar trial across northern New South Wales and South East Queensland, Australia. Pollinations took place in a high density macadamia orchard containing 12 elite genotypes. Each genotype was pollinated using three methods; autogamous pollination, supplementary cross pollination by hand and natural open pollination. INS was recorded 90 days post pollination and FNS 180 days post pollination on 15 racemes tree-1 with 3 reps for each genotype. Pollination methods varied for both INS and FNS. The most efficient pollination method across genotypes was supplementary cross pollination. Autogamous pollination had low INS and lower FNS and the highest mean abscission rate (83.7%). Supplementary cross pollination can increase nut set and cultivars 'HAES 741' and 'HAES 344' were identified as compatible pollinisers. From the elite selections five genotypes were identified as self-fertile by producing nut set through the autogamous pollination method. The greatest difference between the initial and final nut set was for autogamous pollination. Nut set could be utilised for selection of potential high yielding candidate macadamia cultivars.