Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings
Publication Acceptance Date: January 29, 1999
Publication Date: N/A
Interpretive Summary: Improvement of cultivated sunflower can takes place at several levels. One is making selections at the pollen level using large pollen populations to increase the frequency of desirable genes. This would allow breeders an opportunity to shorten the selection and breeding process. Investigations have shown that genes imparting resistance to many biotic and abiotic stresses such as herbicides, salinity, low temperature, and phytotoxins ar expressed in the pollen. A requisite for using pollen is being able to germinate pollen grains for selection to various stresses. The wild sunflower species, the ancestors of the cultivated sunflower, offer a vast genetic resource for improving the sunflower crop, but lack a reliable method of pollen germination. Research was conducted to determine the optimum germination medium and germination technique for wild sunflowers. Preliminary results indicated that macerated stigmas of a cytoplasmic sterile line in a pollen germination medium with polyethylene glycol was effective in germinating fresh pollen of the wild species. It was much less effective on pollen stored under cold conditions for four months. Germinat- ion of wild species did not approach 100% indicating that a single pollen germination technique may not be applicable for all wild species. Stigmas from other cytoplasmic male sterile sources also may be more effective than the one used in the present study. The influence of pollen and stigma sources on pollen germination, whether stigmas can be stored, and the optimum storage conditions need further investigation. The ability to increase pollen germination of some of the wild species gives us the opportunity to explore the sunflower ancestors for desirable traits for improving cultivated sunflower.
Technical Abstract: The wild sunflower species, the ancestors of the cultivated sunflower, offer a vast array of genes for improving the crop. Selection at the gametophytic or pollen (haploid) level would greatly facilitate selection for desirable traits for incorporation into cultivated sunflower. The problem is that a reliable pollen germination technique is needed to exploit the potential of these ancestors. The objective of this study was to develop a pollen germination technique for a wide range of annual and perennial wild sunflower species. A modified technique using a fresh stigma of a cytoplasmic male sterile line and a germination medium containing polyethylene glycol was most effective for inducing pollen germination in wild sunflowers. Preliminary results indicated that the technique was most effective when used on fresh pollen, and less effective on pollen stored four months in liquid nitrogen. The low pollen germination of some species also indicates that a single pollen germination technique for all species may not be applicable. More research is also needed on the influence of pollen and stigmas sources on pollen germination. Preliminary results indicated that the use of fresh stigmas from cytoplasmic male sterile lines significantly increased pollen germination of fresh pollen of wild sunflower species giving us the opportunity to explore the vast genetic resource of the wild species gene pool.