Changes in Pollen Viability and Concomitant Increase in the Incidence of Sorghum Ergot with Flowering Date and Implications in Selection for Escape Resistance

Pollen viability atid ergot severity were ttiotiitored iti a litte evaluatioti nursery at Potchefstroom and Bethlehem (South Africa). Percentage grain fill was also evaluated at the latter locality. Changes in pollen viability with flowering date were closely correlated with changes in ergot severity (r = 0.91 and r = 0.81 at Potchefstroom and Bethlehetn, respectively). Pollen viabihty was significantly reduced by pre-flowering daily minimum temperatures < 16°C at both localities during the period 23- 27 days before flowering. The concomitant increase in ergot severity closely mirrored changes in pollen viability. Lines differed in their ability to tolerate low pre-flowering minimum temperature. Lines with pollen viabilities >60% despite pre-flowering minimum temperature < 14°C were observed. A number of lines with inherent low pollen viabihty, despite minimum temperatures >17°C were also found. Avoiding these in favour of vigourous pollen producers may contribute towards enhancing escape resistance in sorghum to ergot