CROP SCIENCE, VOL. 57, MAY– JUNE 2017 WWW.CROPS.ORG 1455 RESEARCH O ilseed rape is an important crop worldwide that was culti- vated on 35.7 million ha in 2014 (FAOSTAT, 2016). Oilseed rape is Europe’s largest oilseed crop and the second largest protein crop (FAOSTAT, 2016). The yield averages 2 tons ha –1 worldwide, 3.5 tons ha –1 in Western Europe, and 4.0 tons ha –1 in Belgium (FAOSTAT, 2016; FEDIOL, 2016) and depends on the number and the weight of the seeds. Pollination and fertilization are there- fore crucial to optimize yield. Winter oilseed rape cultivars are the most widely cultivated in the world, including in Belgium. The lowering of these winter oi lseed rape cultivars last from 20 to 69 d from early April to June (Delbrassinne and Rasmont, 1988; Man- ning and Boland, 2000). In the indeterminate inlorescences, the most productive lowers are in the lower half of the main raceme (Tayo and Morgan, 1975; Clarke, 1979; Lerin and Rivault, 1982; Williams et al., 1986; Diepenbrock, 2000). This mass-lowering crop is considered to be an insect-pollinated species because it pro- duces nectar in such quantities that bees can use it for abundant production of honey (Calder, 1986; Delaplane and Mayer, 2000; Westcott and Nelson, 2001; Kirk and Howes, 2012). However, the contributions of wind and spontaneous pollination remain under debate (Knuth, 1908; Free and Nuttall, 1968; Langridge and Good- man, 1982; Adegas and Nogueira Couto, 1992; Stefan-Dewenter, 2003; Gallai, 2008; Munawar et al., 2009; Durán et al., 2010; Breeding System and Pollination Biology of Belgian Oilseed Rape Cultivars ( Brassica napus ) Pierre Ouvrard,* M. Quinet, and A.-L. Jacquemart ABSTRACT Oilseed rape (Brassica napus L. ssp napus) is considered to be an insect-pollinated spe- cies, but the degree of insect-dependent pol- lination differs among cultivars and the contri- bution of wind pollination remains a matter of debate. In addition, the breeding system has not been assessed for several new cultivars and spontaneous self-pollination has rarely been addressed. This study aimed to clarify the cur- rent situation in Belgium by analyzing the breed- ing system and pollination biology of the most cropped Belgian cultivars. We performed hand pollination under controlled conditions to ana- lyze the breeding system and conducted ield observations to identify the main pollen vectors. The results show that the studied cultivars were highly self-compatible (self-compatibility index = 1). Nevertheless, pollen vectors were neces- sary to produce high fruit and seed set because spontaneous self-pollination occurred at a low rate under greenhouse conditions. All cultivars produced abundant nectar (1.2 mL per lower per 24 h) with a high sugar content (48%). Surpris- ingly, very few insects were observed: only 1.1% of the lowers received insect visits during their lifespan. Moreover, wind pollination was only responsible for a small portion (2.5%) of the pol- len deposition on stigmas. Despite the lack of pollen vectors, approximately 300 pollen grains were present per stigma. The indirect effects of insects and wind, which favor contact within and between lowers, ensure high fruit and seed set in the main Belgian oilseed rape cultivars. “Genetics, Reproduction, Populations”, Research Team, Earth and Life Institute- Agronomy, Univ. catholique de Louvain, Croix du Sud 2, Box L.7.05.14, 1348 Louvain-la-Neuve, Belgium. Received 2 Sept. 2016. Accepted 23 Jan. 2017. *Corresponding author (pierre.ouvrard@ uclouvain.be). Assigned to Associate Editor Vasu Kuraparthy. Abbreviations: BBCH, Biologische Bundesanstalt, Bundessortenamt and CHemical industry; PL fruit , pollen limitation index for fruit; PL seed , pollen limitation index for seeds; SCI, self-compatibility index; SFI, self-fertility index; W, Kruskal–Wallis test statistic. Published in Crop Sci. 57:1455–1463 (2017). doi: 10.2135/cropsci2016.09.0735 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. Published online June 16, 2017