Development of more productive and persistent lucerne by selection under frequent cutting

Abstract

The area of luceme (Medicago sativa L.), regarded as the best adapted legume for dry areas of New Zealand, has declined by 67% over the last 2 decades. The major reason for the decline has been the effect of pests, diseases and poor grazing management on productivity and persistence. The development of disease- and pest-resistant cultivars has allowed plant breeders to investigate methods for developing grazing-tolerant lucernes. It has been suggested that frequent cutting is harder on plants than grazing and that it could be used to rapidly identify the survival characteristic of breeding lines. Lines surviving cutting every 4 m weeks for 2 seasons have been selected at Lincoln. To evaluate the breeding method these selected lines were compared with their parents, under 4- weekly cutting (frequent), 8-weekly cutting (infrequent) and frequent grazing. Frequent grazing was less severe on plants than frequent cutting and evaluation by this treatment was discontinued after 3 years. There was a trend towards increased production through selection under both frequent and infrequent cutting and there appeared io be line differences in response to selection. Persistence of lines after 7 years of frequent and infrequent cutting was significantly improved by selection for most lines. The different degrees of improvement between lines indicate that lines responded differently to selection. Cutting frequency had little effect on the final plant numbers of lines. The differences between cultivars and lines can be attributed to disease and pest resistance and adaptability of lines. The trial showed that selecting plants tolerant of frequent cutting can improve production and persistence. Keywords: frequent cutting, grazing, Medicago sativa, persistence, production, selection