Genetic improvement of drought survival ability in Phalaris aquatica L

Abstract

The cultivars, Sirocco and Sirolan (or its predecessors) were found to be more persistent than Seedmaster or Australian under drought conditions on the South West and Central West Slopes of New South Wales (NSW). Survival of five cultivars and 150 half sib families through a severe drought at Temora was negatively correlated with the level of regrowth activity of the underground buds after summer rainfall (r = -0.25, P < 0.01). The families from which the parents of Sirolan were selected were as drought hardy as Sirocco, but regenerated more actively after summer rain. Reduced summer dormancy appeared to be advantageous for the establishment of PX 17 U, a predecessor population four generations removed from the 32 plants which produce breeders' seed of Sirolan, relative to that of Sirocco, when both were sown under a cover crop of wheat near Stockinbingal, NSW. In the second winter, the plants of the breeding population were larger and more frequent than those of Sirocco, apparently because they regenerated more actively in late summer and hence competed more successfully against the resident annual ryegrass population. These differences were still apparent four years later. Sirocco and Sirolan also persisted better than Sirosa and Australian phalaris and cultivars of tall fescue and cocksfoot through the 1980-81 droughts near Mendooran and Binnaway, NSW. Under favourable conditions near Canberra, Sirocco, El Golea, Sirolan and Sirosa were more productive during autumn and winter than Seedmaster. Sirocco and Sirolan appear to have somewhat different drought-escaping mechanisms, and the effectiveness of these systems for ensuring survival under different drought conditions is discussed.