The self fertility status of some sunflower cultivars in Australia

Abstract

Abstract Sunflower self fertility, as measured by the effects of autogamous pollination and genetic self compatibility, was found to vary between hybrids and between seasons. Of 24 hybrids tested under uniform fertile, irrigated conditions, only two achieved high yields without honey bees. Three were self fertile in terms of seed numbers. Seven achieved self fertility in terms of seed yield due to artifact effects (e.g. compensatory seed growth), and of these only three were high-yielding and satisfactory agronomically. A good seed set of 80% or more in terms of seed number needs to be supported by an artifact ratio (AR) for self fertility (% by weight divided by % by number) of between 1.25 and 1.30 to ensure 100% self fertility in terms of seed yield. For Sunfola 68.2, the open-pollinated cultivar, and for most of the 23 hybrid cultivars examined, a significant positive response in seed set was obtained due to the presence of honey bees. For exclusion of insects tulle net bags were greatly superior to paper bags, and for trials on farmers' properties bags were much easier to use than cages. Pollination due to wind and insects smaller than honey bees did not exceed 9%, confirming that wind was of neglegible importance, and that the honey bee was the principal insect pollinator. Consequently, until self fertility is achieved genetically under a wide range of environmental conditions, honey bees are needed to maximize sunflower yields, especially under ideal growing conditions.