May 7, 2009 - News release: Update on Pollination Variations in Three White Maize Hybrids in South Africa

As previously reported, three white maize hybrids (DKC78-35R, DKC78-45BR and DKC77-71R) showed variable pollination (kernel set) in some farmers’ fields during the 2008/2009 growing season in South Africa. Based on our survey of these fields, we determined that the variation in pollination resulted in an average yield reduction of around 25 percent in fields where variable pollination occurred.

In an effort to determine the cause of the variable pollination, we conducted extensive observations and research including an evaluation for the presence of the biotechnology traits (YieldGard^® and Roundup Ready^®) in these hybrids. The data conclusively showed that the biotechnology traits were not responsible for the variable pollination observed in some farmers’ fields this year.

We further evaluated these three hybrids and the parental inbred lines and determined that the reduced pollen viability was caused by the naturally occurring condition known as cytoplasmic male sterility (CMS). This naturally occurring system which controls pollination through pollen sterility are found in over 150 plant species, including many crop species. It has been known for about 80 years in maize. The maize system has been used by the seed industry for many years to circumvent the labor-intensive need to remove the tassel (the pollen-producing structure) from the female parent in hybrid seed production fields. These practices (de-tasseling or using CMS) ensure pollination by the male parent inbred only –essential for hybrid production- and the CMS system tends to improve hybrid seed purity and quality.

As previously reported, the hybrids in question were produced by reversing the male and female parents. CMS can be passed to hybrid seed only through the female line. The female used in the breeding of the three hybrids contained CMS that was not previously detected. Then a combination of other factors, including weather and farming practices, reduced the pollen production still further. Thus, the three resulting hybrid varieties exhibited variable levels of pollination in some farmers’ fields which in turn reduced yields.

In the future, the CMS-containing plant line will not be used as a female in hybrid seed production. This will solve the problem in future growing seasons. Monsanto also has tested all white and yellow maize seed offerings in South Africa, and the female line in question is the only one with CMS.