The utilization of heterosis for seed yield in hybrid and synthetic cultivars of summer turnip rape

Abstract

Hybrids of summer turnip rape (Brassica rapa L. syn. B. campestris L.) have been shown to exhibit high levels of heterosis. This study was undertaken to determine whether the heterosis for seed yield observed in hybrids could be captured by synthetic cultivars of turnip rape. The agronomic performance of reciprocal inter-cultivar hybrids and their corresponding two-component synthetics was studied using four turnip rape cultivars. Hybrid seed was produced by hand pollination in the greenhouse and Syn1 seed was produced by mixing equal proportions of each parent to form the base seed (Syn0) of each synthetic, and planting these in isolation in the field. The seed yield of hybrids, synthetics and parents were similar in 1985 while in 1986, hybrids yielded 25% and synthetics 23% more than parents. Actual versus predicted synthetic yields were similar except for one synthetic, Echo-Torch in 1986, where the actual yield exceeded the predicted value. Hybrid yields may have been underestimated by the chosen prediction method and therefore the yield potential of hybrids would be greater than for synthetics in turnip rape. However, until a suitable pollination control system is developed in this species, synthetic cultivars are a viable alternative to hybrids. Key words: Turnip rape (summer), synthetic, hybrids, Brassica rapa, B. campestris