Breeding disease resistant, aphid resistant lucerne for subtropical Queensland

Abstract

The breeding and preliminary evaluation of two new lucerne cultivars are described. Each is shown to possess a satisfactory level of resistance to Phytophthora megasperma f.sp. medicaginis (Phytophthora root rot), Colletotrichum trifolii (Colletotrichum crown rot), Therioaphis trifolii f, maculata (spotted alfalfa aphid) and Acyrthosiphon pisum (pea aphid) and a lower but adequate level of resistance to A. kondoi (blue-green aphid). The first cultivar, code-named APC Cycle 3 and subsequently released as cv. Trifecta, is a broadly based cultivar with a genetic background substantially based on cv. Hunter River. In a field trial at Gatton Research Station, it outyielded cv. CUF 101 by 19%, cv. Siriver by 24% and cv. Hunter River threefold over a 16-month period, and persisted significantly better than those cultivars. It showed some winter activity and was classified as winter active in Queensland. Polycross progeny testing showed that APC Cycle 3 contains significant genetic diversity for yield and persistence, and further response to selection for these characters could be obtained. Heritabilities ranged from 0.79 to 0.86 for yield and persistence. A positive genetic correlation (rg= 0.87) between winter yield and main season yield was measured, and yield was positively correlated genetically with persistence. The second cultivar, code-named SP Cycle 3 and subsequently released as cv. Sequel, was derived from cvv. Siro Peruvian and CUF 101. It is highly winter active.