Impact of Plant Breeding on the Grain Yield and Genetic Diversity of Spring Oats1

Abstract

The genetic relationships among, and grain yields of spring oat (Avena sativa L.) cultivars released in the north central and northeastern USA between 1941 and 1980 were investigated using coefficients of parentage (r) and least squares means (LSM). These parameters were evaluated in two data sets, Early and Midseason, which were based on uniform regional nursery trials conducted between 1944 and 1980. The mean coefficient of parentage (r̄) among oat cultivars released within the same 5‐year period has oscillated between approximately 0.1 and 0.3 since the mid‐1940's in each data set with no apparent long‐term positive or negative trend. The level of r̄ during 1976–1980 was 0.22 and 0.13 in the Early and Midseason data sets, respectively. The LSM's were used to estimate genotypic value for grain yield of each cultivar tested for 3 or more years. The LSM's of cultivars released within the same 5‐year period were averaged (x̄LSM) and compared with the LSM of ‘Gopher’ (LSMG), a selection from the 19th century cultivar ‘Kherson’. Increases in x̄LSM were relatively modest from 1941 to 1975. In the 1971–1975 period, the x̄LSM's were 116 and 111% of LSMG for the Early and Midseason data sets, respectively. However, in the 1976–1980 period, a substantial increase in x̄LSM to 134% of LSMG was observed in the Early data set indicating a genetic gain during this 5‐year period which equaled that of the entire 35‐year period prior to 1976. A breakthrough in yield was also suggested in the Midseason data set because two recently released cultivars, ‘Ogle’ and ‘Porter’, had LSM's ≥130% of LSMG. The recent large increases in oat grain yield were obtained over a broad base of germplasm. Coefficients of parentage among the five cultivars having LSM's ≥130% of LSMG indicated that a minimum of three distinct sources of germplasm with high yield potential was involved.