Recurrent selection for grazing tolerance in winter-active populations of the perennial grass, Phalaris aquatica L.

Abstract

Phalaris (Phalaris aquatica L.) is a perennial grass of Mediterranean origin used widely by the sheep and cattle industries of south-eastern Australia. Winter-active cultivars released since the 1970's have the potential for higher herbage productivity than the earlier, semi-winter dormant cultivars but have been reported to be less persistent under sub-optimal grazing management and soil conditions. To improve genetic potential for persistence in winter-active phalaris, a program of recurrent selection was conducted by subjecting three populations of half-sib families to two cycles of selection for persistence under heavy, largely continuous grazing pressure. Cycle 2 progeny families and bulked seedlots of each generation were grown in separate grazed plot trials in Western Victoria and the Southern Tablelands and North-West Slopes of New South Wales from 1999-2003 to assess response to selection. Positive linear response to selection was observed in all populations at the Western Victorian and Southern Tablelands sites. Response to selection was absent and persistence was very low under higher temperature and drought stress on the North-West Slopes. This high level of genotype × environment interaction for persistence was also observed among final generation families. Families with better persistence than current winteractive cultivars at the two southern sites were identified in each population and a new cultivar is being formed from the parents.