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

Abstract

. 1998. The utilization of heterosis for seed yield in hybrid and synthetic cultivars of summer turnip rape. Can. J. Plant Sci. 78: 383-387. 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 Syn 1 seed was produced by mixing equal proportions of each parent to form the base seed (Syn 0 ) 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. Nous avons observé, chez quatre cultivars de navette, le comportement agronomique d'hybrides simples réciproques de cultivars et de leurs synthétiques correspondants. Les semences hybrides étaient produites en serre par pollinisation manuelle et les semences Syn 1 étaient le produit de la culture au champ en condition d'isolement des semences Syn 0 formées du mélange en proportion, égale, des graines de chaque parent. Le rendement grainier des hybrides synthétiques et des cultivars parentaux était comparable en 1985, mais en 1986 les hybrides produisaient 25 % et les synthétiques 23 % de plus que les cultivars parentaux. Les rendements réels et prédits des synthétiques correspondaient, sauf en 1986 pour le synthétique Echo-Torch dont le rendement réel dépassait les prédictions. Il est possible que la méthode de prédiction choisie ait sousestimé le rendement des hybrides dans le cas de la navette d'été et que les potentialités de rendement des hybrides soient effectivement plus grandes que celles des synthétiques. Mais, en attendant la mise au point d'un système convenable de maîtrise de la pollinisation pour cette espèce, les cultivars synthétiques constituent une alternative valable et viable aux hybrides.

Genetic variability of Canadian elite cultivars of summer turnip rape (Brassica rapa L.) revealed by simple sequence repeat markers

“…Higher seed yields are required to increase the competitiveness of B. rapa cultivars, and this represents a great challenge for B. rapa oilseed breeding (Dewan et al 1998). One feasible approach is to develop hybrid B. rapa cultivars (Hutcheson et al 1981); however, the success of this approach requires a better understanding of the seed yield potential and genetic variability of either hybrid or synthetic cultivars (Falk et al 1998;Warwick et al 2008).…”

Revitalizing the winter turnip rape crop in the northern latitudes

“…The commercial production of F 1 hydrids based on male sterility depends on repeated back-crossing of an inbred maintainer line into the cytoplasmic male-sterile A-line, and the production of highly inbred restorer lines. High levels of heterosis have been achieved in F 1 hybrids of spring turnip rape (25%; Falk et al, 1998) and other forms of the species such as Chinese cabbage. With less investment effort, almost as much heterosis can be captured in composite and synthetic cultivars (23%; Falk et al, 1998), where two or more inbred lines are mixed and allowed to cross-pollinate in the production of foundation seed.…”

“…High levels of heterosis have been achieved in F 1 hybrids of spring turnip rape (25%; Falk et al, 1998) and other forms of the species such as Chinese cabbage. With less investment effort, almost as much heterosis can be captured in composite and synthetic cultivars (23%; Falk et al, 1998), where two or more inbred lines are mixed and allowed to cross-pollinate in the production of foundation seed. This strategy has been applied to spring turnip rape in Canada (Falk et al, 2002) and Finland (Niemelä et al, 2006).…”

Yield potential of spring turnip rape synthetics and composite hybrids compared with open-pollinated commercial cultivars

“…Synthetics are formed by mechanically mixing two or three parental lines (Buzza 1995) to constitute the Syn 1 generation, which is generally the commercial seed. The heterotic impact of synthetic cultivars of summer turnip rape on seed yield has been demonstrated recently by Falk et al (1998) and by Falk and Woods (2003). In these studies, however, not all the turnip rape material met the quality requirements of low erucic acid and low glucosinolate content.…”

“…Turnip rape is self-incompatible and traditionally most of the commercial cultivars are open-pollinated, heterotic populations. During the 1980s and 1990s, significant heterosis was reported in a large number of studies in oilseed rape, B. napus L. (Sernyk and Stefansson 1983;Grant and Beversdorf 1985;Brandle and McVetty 1989) and in turnip rape (Hutcheson et al 1981;Schuler et al 1992;Falk et al 1994Falk et al , 1998. Attempts to exploit heterosis to produce higheryielding cultivars led to the development of synthetic and hybrid cultivars of oilseed rape and turnip rape.…”