Apis mellifera (Hymenoptera: Apidae) as a potential Brassica napus pollinator (cv. Hyola 432) (Brassicaceae), in Southern Brazil

Abstract

Brassica napus Linnaeus is considered a self-compatible crop; however, studies show that bee foraging elevates their seed production. Considering bee food shortages during the winter season and that the canola is a winter crop, this study aimed to evaluate the foraging behaviour of Apis mellifera Linnaeus, 1758 regarding those flowers, and to verify if it presents adequate behaviour for successfully pollinating this crop in Rio Grande do Sul State. The study was carried out in a canola field, in Southern Brazil. The anthesis stages were morphologically characterised and then related to stigma receptivity and pollen grain viability. Similarly, the behaviour of A. mellifera individuals on flowers was followed, considering the number of flowers visited per plant, the amount of time spent on the flowers, touched structures, and collected resources. Floral fidelity was inferred by analysing the pollen load of bees collected on flowers. The bees visited from 1-7 flowers/plant (x = 2.02; sd = 1.16), the time spent on the flowers varied between 1-43 seconds (x = 3.29; sd = 2.36) and, when seeking nectar and pollen, they invariably touched anthers and stigmas. The pollen load presented 100% of B. napus pollen. The bees' attendance to a small number of flowers/plants, their short permanence on flowers, their contact with anthers and stigma and the integral floral constancy allows their consideration as potential B. napus pollinators.Keywords: behavior, canola, honey bees, anthesis, pollination.Apis mellifera (Hymenoptera: Apidae) como potencial polinizador de Brassica napus (cv. Hyola 432) (Brassicaceae), no Sul do Brasil ResumoBrassica napus Linnaeus é considerada uma cultura autocompatível, entretanto, estudos indicam que o forrageio de abelhas eleva sua produtividade de sementes. Considerando-se a escassez de alimento para abelhas no inverno e a canola sendo uma cultura desse período, objetivou-se avaliar o comportamento de forrageio de Apis mellifera Linnaeus, 1758 nas suas flores e verificar se apresenta comportamento propício ao sucesso de polinização dessa cultura no Rio Grande do Sul. O estudo foi desenvolvido em lavoura de canola, no Sul do Brasil. Os estágios da antese foram caracterizados morfologicamente e relacionados à receptividade do estigma e à viabilidade dos grãos de pólen. Paralelamente, o comportamento de indivíduos de A. mellifera nas flores foi acompanhado, considerando-se o número de flores visitadas por planta, o tempo de permanência nas flores, as estruturas tocadas e os recursos coletados. A fidelidade floral foi inferida analisando-se a carga polínica de abelhas coletadas em flores. As abelhas visitaram entre 1-7 flores/planta (x = 2,02; sd = 1,16), o tempo de permanência nas flores variou entre 1-43 segundos (x = 3,29; sd = 2,36) e, ao buscarem néctar e pólen, invariavelmente tocavam anteras e estigmas. A carga polínica apresentou 100% de pólen de B. napus. A visita a poucas flores/planta, a curta permanência sobre as flores, o contato das abelhas com anteras e estigma e a plena constâ...

Comparative study of the floral biology and of the response of productivity to insect visitation in two rapeseed cultivars (Brassica napus L.) in Rio Grande do Sul

“…Additionally, both cultivars displayed pistil growth as the flowers matured, which resulted in growth of the stigma to the same size as the anthers, then surpassing them, as observed in other studies (Rosa et al, 2010).…”

“…In addition to pistil growth, torsion of the stamens was observed, positioning the dehiscent side of the anthers toward the flower's exterior, as reported in other studies on rapeseed (Mussury and Fernandes, 2000;Rosa et al, 2010). When the flowers were partially open, the anthers of the long stamens faced inward, though some flowers also displayed anthers facing outward.…”

“…Other rapeseed cultivars have been reported to show different anthesis periods. For example, CTC-4 has been reported by different authors to exhibit an anthesis period of 32.5 ± 8.6 hours (Adegas and Nogueira Couto, 1992) or 48 hours (Mussury and Fernandes, 2000), and Hyola 432 shows an anthesis period of 72 hours (Rosa et al, 2010).…”

“…Rapeseed (Brassica napus L., Brassicaceae) is an agricultural crop that benefits from animal pollination (Kevan and Eisikowitch, 1990;Adegas and Nogueira Couto, 1992;Durán et al, 2010;Rosa et al, 2010Rosa et al, , 2011Ali et al, 2011;Bommarco et al, 2012). It is the third most highly produced oleaginous plant worldwide (Tomm, 2005).…”

“…However, several studies have shown that insect pollination of these flowers increases the amounts of seeds produced (Kevan and Eisikowitch, 1990;Rosa et al, 2010;Ali et al, 2011), seed weight and quality (amount of oil) (Durán et al, 2010;Bommarco et al, 2012) and even the seed germination rate (Kevan and Eisikowitch, 1990), resulting in higher market values (Bommarco et al, 2012).…”