Sterility in winter wheat: Review of occurrence in different varieties and possible causes

Summary

This review examines the sterility observed in winter wheat in the UK in the variety Moulin in the mid-1980's and in trials in Northern Scotland in 1997. The review suggests that, although sterility appears to result from a failure of pollen development instigated at or around meiosis, a number of factors contribute to the problem. An examination is made of the possibility of a repetition of sterility in the UK and of the capability of the official trials system to identify varieties with a proclivity to sterility. In addition to investigating examples of high levels of sterility in wheat, the review concluded that 'sub-clinical' sterility cannot be ruled out by an examination of trials data and may be a factor in yield variation in certain varieties.

Sterility in wheat generally affects the male although other factors, such as female sterility, could play a part. Although sterility is triggered by environmental factors, the problem is of genetic origin. More than one gene appears to be involved with unadapted germplasm the likely source. It is unlikely that the specific male sterility genes used in hybrid wheat production are the cause. It has been postulated that the dwarfing (Rht) genes may be a factor: possibly through allowing gibberellic acid accumulation to levels, which affect anther development adversely. The frequent use of Rht genes in wheat, however, suggests that they are not the prime cause. On the other hand, they may be a contributory factor because improved levels of spikelet fertility associated with semi-dwarfs seem to be more vulnerable to environmental effects than in other varieties.

Many environmental factors have been thought to affect fertility in wheat. These include increases and reductions in temperature; reductions in light, water, boron and copper; the use of plant growth regulators, fungicides or herbicides; attacks by the orange blossom midge. The review has eliminated plant growth regulators and fungicides as causing sterility in the RL trials because untreated and treated trials were similarly affected by sterility in Moulin and in 1997. Reductions in temperature, light or boron can certainly cause sterility under experimental conditions. Low boron may be a prime cause of sterility with low light and temperature being responsible for inducing such a condition through their adverse influence on transpiration and thereby boron uptake. However this link needs to be established.

It was concluded that the existing RL trialling system is adequate to detect varieties with serious tendencies to male sterility.