Selection for seed retention in Phalaris tuberosa L.

Abstract

Loss of seed from the maturing inflorescence (seed shattering) is common in grasses and constitutes a serious economic problem in many species. This paper reports the results of artificial selection to improve seed retention in Phalaris tuberosa, an important perennial grass in south-eastern Australia.

A study of the factors controlling the loss of seed in this species has revealed that the seed lies free within the inflorescence at maturity, and its loss is promoted by the opening of the glumes. This in turn is influenced by the structure of the inflorescence. The highest seed retention has been found in plants with a short rigid inflorescence containing a large number of densely packed spikelets.

Wide variation for seed retention exists between strains of P. tuberosa. The lowest value (25%) was found for natural ecotypes from Algeria and Morocco, and the highest for a selection from a strain of the Australian commercial type obtained from Argentina (81%). An estimate of the heritability for seed retention was high (0.92 ± 0.11), and most of the genetic variation appeared to be additive. There was a marked response to selection for high seed retention. With the Argentine variety as the base population, an increase of 29% in the average level of seed retention was achieved from the first cycle of selection. This level represents an increase of 60% by comparison with the widely grown commercial strain. The importance of high seed retention in relation to the economics of Phalaris seed production is briefly discussed.