J. Le Guen

Present status and future strategy in breeding faba beans (Vicia faba L.) for resistance to biotic and abiotic stresses

Progress is being made, mainly by ICARDA but also elsewhere, in breeding for resistance to Botrytis, AScochyta, Uromyces, and Orobanche; and some lines have resistance to more than one pathogen. The strategy is to extend multiple resistance but also to seek new and durable forms of resistance. Internationally coordinated programs are needed to maintain the momentum of this work.

Genetic variability for feeding value of faba bean seeds ( Vicia faba ): Comparative chemical composition of isogenics involving zero-tannin and zero-vicine genes

In a preliminary experiment, 74 faba bean genotypes including winter genotypes (autumn-sown) and spring genotypes (spring-sown) and isogenic population pairs (tannin-containing v . tannin-free and vicine/convicine-high v . vicine/convicine-low), were analysed for the chemical composition of their seeds. A large variability was found for the main constituents (starch, protein and fibre). Autumn-sown genotypes contained 2·3% less proteins but 2·5% more starch in the seed dry matter (DM) than spring-sown genotypes. The vc − gene, which lowers the vicine and convicine contents, did not significantly modify the main seed components in the isogenic comparisons. The zt1 and zt2 genes, which eliminate condensed tannins in the seed coats, lowered by 2·1% the proportion of the seed coat in the DM. In the isogenic comparisons, the zt2 gene had a stronger effect than zt1 in reducing the total seed fibre and increasing the protein content. In a second experiment, from the original 74 genotypes, 12 contrasted genotypes were selected and multiplied for animal nutrition trials. Their chemical analysis confirmed the variability between the faba bean categories observed in Expt 1, but detailed chemical analyses illustrated the variability in amino acid, fatty acid, amylose and oligosaccharide composition, trypsin inhibitory activity, condensed tannins, lectins and phytic phosphorus contents.

Variation in outcrossing levels in faba bean cultivars: role of ecological factors

Understanding the role of pollinators in determining the outcrossing rate is very important for the development of synthetic varieties of faba bean. Isozyme markers have been used to study the multilocus outcrossing rate in five cultivars under field conditions and in two locations. The study was carried out at Cordoba (Spain) and at Rennes (France). These two locations were chosen because previously studies showed strong differences in cross-pollination. Multilocus outcrossing rates at both locations, Cordoba and Rennes, were 0.65 and 0.33 respectively. Local differences in pollinator abundance and foraging activity were 26 and 32 times higher, respectively, at Cordoba than at Rennes which could explain an outcrossing rate twice at Cordoba compared with Rennes. So, pollinators may play a prominent role in determining the differences in outcrossing between locations. However, at a local level, there is a highly significant positive correlation between foraging activity and outcrossing only at Rennes (where the number of pollinators is scarce) but not at Cordoba (where pollinators are abundant). We suggest that although pollinators have a major impact on the level of outcrossing, in circumstances where there are a lot of pollinators the differences in outcrossing between cultivars depends on other factors among which is the ability of the genotype itself to outcross. No type of floral display seems to be clearly important in the determination of the outcrossing level in such a case. The implication of our results for faba bean breeding strategies is discussed.

Influence des facteurs climatiques sur la phenologie de la feverole (Vicia faba (L.))

This study is an analysis of 33 years (1953–1985) of phenological data for faba bean (Vicia faba (L.)), variety Ascott, grown at Rennes, in western France. The effects of temperature, radiation and water balance on the duration of “sowing to emergence”, “emergence to start of flowering”, “flowering”, “end of flowering to start of ripening” and “start of ripening to harvest” were found. Temperature acts on all the stages with “emergence to start of flowering”, “flowering” and the post-flowering period being the most sensitive. By assuming a linear response to temperature, the base temperatures for each stage were found by four different methods. The bases were near 0°C for “sowing to emergence”, but rose to ∼ 12°C for “end of flowering to start of maturity”. High evaporation rates reduced the duration of periods involving flowering. High rainfall extended the flowering and maturation periods. High solar radiation made the onset of maturity quicker. Linear regression equations relating the duration of the phases and weather were derived and applied to independent data at Rennes and Dijon in 1987.

Influence des facteurs climatiques sur le rendement de la féverole (Vicia faba L. var. ‘Ascott’) et ses composantes

The yield and yield components of a spring bean cultivar (Vicia faba L. cv. ‘Ascott’) grown in Rennes, western France, were collected for 33 years (1953–1985). Variability in these components has been related to climatic factors during different growth stages: until the beginning of flowering, high rainfall promotes yield and seed number per ground area, but incident radiation is negatively correlated with these components and to thousand seed weight; flowering is not a very sensitive stage; high air humidity is prejudicial to thousand seed weight and a large daily temperature variation reduces seed number but not final yield; for the largest yield, the period from the end of flowering to the beginning of ripening must last as long as possible with moderate temperatures (effects on thousand seed weight) and low water deficits (effects on seed number); from the beginning of ripening, heat shocks up to 30°C reduce yields. General diagrams are presented to show the role of different climatic factors.

Variety X Environment Interaction in Vicia faba in Relation to the Genetic Structure of Varieties

Yield stability is an important character to breed into field beans. This stability depends on various parameters among which genetical structure predominates.