Multi-Site Evaluation on Acid Soils of a Phalaris Aquatica x P. Arundinacea x P. Aquatica Backcross Population Bred for Acid Soil Tolerance

Half-sib families in the AT98 Phalaris aquatica × P. arundinacea × P. aquatica backcross population bred for acid soil tolerance were compared for establishment, persistence, and yield with phalaris (P. aquatica L.) controls and cocksfoot (Dactylis glomerata L. cv. Porto) at 4 sites in south-eastern Australia with the aim of selecting the parents of a new cultivar. The sites had strongly acid soils but differed in parent material, pH profile, soil fertility, and suitability for phalaris. Establishment by AT98 was clearly superior to all phalaris controls and similar to cocksfoot in an acid soil high in Al to depth at Chiltern, north-eastern Victoria, after sowing in early spring 2000. It was considered likely that better establishment by AT98 was due to its higher Al tolerance. In contrast, little variation in establishment was observed at 3 other sites sown in late autumn 1999, possibly due to a longer period free of moisture stress compared with the later sown Chiltern site. Once established, the control cultivars of phalaris at the autumn-sown sites in general persisted and yielded similarly to the mean of the AT98 families. Significant family variation was observed and predicted heritability on a family mean basis was high for persistence measured as basal frequency and moderately high for yield in the third year. Family by site interaction was relatively low for both attributes. A cultivar based on the best families should give more reliable establishment on acid soils high in Al under conditions where rapid root growth to depth is needed for survival, and give more flexibility of sowing date on these soils. Its best performance relative to cv. Landmaster in terms of third-year yield was predicted to occur on granite-derived soils in north-eastern Victoria.