Modalités de la pollinisation chez deux lignées de féverole de printemps ( Vicia faba L var equina Steudel). Effets sur les coulures, la productivité et les taux de croisementsJ. Mesquidaa, J. Le Guenb, J.N. Taseic, S. Carrec and G. Morinb
a INRA, centre de recherches de Rennes, laboratoire de zoologie, 35650 Le Rheu, France
b INRA, centre de recherches de Rennes, station d'amélioration des plantes, domaine de la Motte au Vicomte, BP 29, 35650 Le Rheu, France
c INRA, centre de recherches de Poitou-Charentes, laboratoire de Zoologie, F 86600 Lusignan, France
Abstract - Effect of pollination treatments on reproductive organ abortion rates, yield and crossing rates in 2 lines of spring faba bean (Vicia faba L var equina Steudel)
The effects of 5 pollination treatments on reproductive organ abortion rates, fruiting rate, yield components and crossing were studied in a self-pollinating (D-27) and a non self-pollinating (D-23) line of faba bean. The experimental design consisted of a completely randomized block with 3 replications, 5 treatments and 2 varieties per treatment. Pollination treatments were as follows: 1) cages with honeybees (Apis mellifera L) (a small hive consisting of 5 frames of honeybees per cage), 2) cages with bumblebees (2 queens of Bombus lapidarius L per cage), 3) cages without insects (self-pollination), 4) cages without insects but hand pollinated (= tripped), 5) outside standard open pollination. Cages used in this experiment were 3 × 3 × 2 m (L × W × H) and made of 2-mm mesh cloth. Two rows of 10 plants for each of the 2 lines were sown in each cage. Observations were conducted on insect foraging behaviour, abortion rate of reproductive organs (nodes, flowers and pods) for 5 plants per line, per treatment and per block. In all cages with honeybees, flower abortions at the bottom of the plants were significantly higher than at the top (38% and 13% at the bottom versus 13% and 5% at the top for D-27 lines and D-23 line respectively), indicating possible "over visitation" due to overpopulation (bees/plant) of honeybees per cage. Line D-27 showed a greater susceptibility to flower abortion than line D-23. When compared to selfing, entomophilous pollination (honeybees or bumblebees) had no significant effect on flower abortion, pod set and yield components for line D-27. Self-pollination was thus considered predominant in this genotype. This genotype also seemed to possess good capacities for compensation when exposed to various environmental conditions. In contrast, entomophilous pollination appeared necessary for line D-23. In the absence of bees, the abortion rate of yound pods (< 2 cm long) increased significantly (83% vs 33% with honeybees and 32% with bumblebees, P = 0.001). The same was also observed for older pods (> 2 cm long; 28% vs 4 and 7%, P = 0.01 but less than 4 cm long). Absolute abortion rate was higher under selfing conditions when compared to insect pollination (86% vs 41 and 39%, P = 0.001). With self-pollination there was a significant restriction of the pod setting rate (8.6 vs 69.4 and 80.2, P = 0.001), the number of seeds per pod (2.25 vs 2.83 and 3.12, P = 0.001) and the yield (5.7 vs 31.1 and 33.5, P = 0.001). Nevertheless, fructification for this line under self-pollination (ie without insects or tripping) was 23% of that with insects. The outcrossing rate of line D-27 by line D-23 was = 10% in treatments 1 or 2 and 5% in treatment 5.
Key words: Apis mellifera / Bombus / pollination / organ abortion / Vicia faba