Genetic diversity of South African winter wheat cultivars in relation to preharvest sprouting and falling number

The falling number method, which is widely used to estimate alpha-amylase activity in wheat grain, was officially introduced as part of the South African grading regulations in 1998. The preceding two seasons had been characterised by abnormally wet conditions during harvest time, especially in the eastern parts of the Free State, resulting in major preharvest sprouting problems. Downgrading due to a low falling number is an intermittent problem in South Africa. In this study South African winter wheat cultivars were screened for their preharvest sprouting resistance in comparison with their inherent falling number. Wheat cultivars varied substantially in their ability to withstand moist harvest conditions. The falling number of cultivars which were exposed to optimal conditions for preharvest sprouting by using a rain simulator, dropped drastically in most cases. It is generally accepted that the long-term solution to this problem lies in the development of cultivars which are able to tolerate or resist the damaging effects of rain during the period between ripeness of maturity and the completion of harvest. By using the data generated from this study, it will be possible to select for more tolerant types which can be used in the development of cultivars with an inherently higher falling number.