Honey bee contribution to canola pollination in Southern Brazil

Abstract

Although canola, (Brassica napus L.), is considered a self-pollinating crop, researchers have indicated that crop productivity increases as a result of honey bee Apis mellifera L. pollination. Given this crop's growing importance in Rio Grande do Sul State, Brazil, this work evaluated the increase in pod and seed productivity with respect to interactions with anthophilous insects and manual pollination tests. The visiting frequency of A. mellifera was correlated with the crop's blooming progression, and productivity comparisons were made between plants visited by insects, manually pollinated plants (geitonogamy and xenogamy) and plants without pollination induction. Pod set and seed production per plant were determined for each treatment. Among the 8,624 recorded flower-visiting insects, Hymenoptera representatives were the most prevalent (92.3%), among which 99.8% were A. mellifera. The correlation between these bees and blooming progression was positive (r = 0.87; p = 0.002). Pollination induction increased seed productivity from 28.4% (autogamy) to 50.4% with insect visitations, as well as to 48.7 (geitonogamy) and to 55.1% (xenogamy) through manual pollination. Key words: flower-visiting insects, blooming, canola productivity Abelhas melíferas na polinização de canola no Sul do Brasil RESUMO: A canola (Brassica napus L.) é considerada autocompatível, embora pesquisadores indiquem aumento na produtividade da cultura resultante da polinização efetuada por Apis mellifera L.. Considerando-se a crescente importância dessa cultura no Rio Grande do Sul, avaliou-se o incremento da produtividade de síliquas e sementes a partir de interações com insetos antófilos e com testes de polinização manual. A freqüência de visitas de A. mellifera foi relacionada com o desenvolvimento da floração da cultura e a produtividade foi comparada entre plantas visitadas por insetos, polinizadas manualmente (geitonogamia e xenogamia) e com ausência de indução de polinização. Em cada tratamento avaliou-se a produtividade de síliquas e de sementes formadas por planta. Dentre os 8.624 insetos visitantes florais registrados destacaram-se representantes de Hymenoptera (92,3%), dos quais 99,8% eram A. mellifera. A relação entre essas abelhas e o curso da floração foi positiva (r = 0,87; p = 0,002). A indução de polinização elevou a produtividade de sementes de 28,3% (autogamia) para 50,4% com livre visita de insetos e com polinização manual, respectivamente, para 48,7 (geitonogamia) e 55,1% (xenogamia). Palavras-chave: insetos visitantes florais, floração, produtividade agrícola

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

“…Experiments in the CTC-4 cultivar showed similar results (Adegas and Nogueira Couto, 1992). However, at Guarani das Missões (Hyola 61), the free visitation and xenogamy treatments resulted in higher production of seeds per silique (see Table 1), as has previously been observed for the Hyola 432 cultivar, to which free visitation conditions were shown to increase the numbers of seeds present in the siliques (Rosa et al, 2011). Durán et al (2010) also reported a greater number of seeds per silique when free insect visitation was allowed for flowers of the Artus cultivar.…”

“…For example, Mussury and Fernandes (2000) observed that pollination may occur during pre-anthesis, as flowers already presented dehiscent anthers at this time. Several studies have shown that even without visitation by pollinators, there is formation of siliques and seeds (Adegas and Nogueira Couto, 1992;Bommarco et al, 2012); nevertheless, as mentioned above and also shown in the present study, production is increased when insect pollination occurs (Adegas and Nogueira Couto, 1992;Durán et al, 2010;Rosa et al, 2011;Bommarco et al, 2012;Jauker et al, 2012). However, the positive effects on seed production and quality may vary between cultivars and plantation sites, as differences in the number of seeds per silique and seed weight were found between the study sites (see Figures 1 to 6).…”

“…Similar results have been found by other researchers. For the Hyola 432 cultivar, a treatment allowing free visitation by insects (mainly A. mellifera) was found to increase the percentage of siliques formed by 22% compared to autogamy (Rosa et al, 2011).…”

“…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).…”

Diversity of insect pollinators with reference to their impact on yield production of canola (Brassica napus L.) in Ismailia, Egypt

“…Pollination of canola can have positive effects, such as shortening of the period of flowering and raceme production, acceleration of ripening, increase in seed weight (Rosa et al, 2011;Bommarco et al, 2012), seed oil content (Bommarco et al, 2012) and seed yield. Klein et al (2007) highlighted the importance of insect pollination for the production of fruits and seeds.…”