Faba bean

Abstract

Faba bean is a cool-season annual grain legume that originated in the southwestern Asia. It is now grown on all continents but on only 2.5 Mha when compared with 5.5 Mha in 1960. The largest production is in Mediterranean environments, but it is also grown in high altitude subtropical environments and extends to cold-temperate areas. Faba bean is a productive C3 species with maximum crop growth rates of 25–30 g m− 2 d− 1, yields of 6–7 t ha− 1, and RUE reaching 1.79–1.85 g MJ− 1 PAR. It is, however, sensitive to moisture stress and to high and low temperature. Temperature range for growth is 5–35°C with optimum temperature for photosynthesis of 25°C. Flowering is destroyed by frost, and few cultivars can tolerate temperatures <–10°C. Current cultivars are grouped in two ways. First, phenologically as spring, Mediterranean and winter types according to a zero, mild, or strong vernalisation requirement for flowering. These groups provide adaptation, respectively, to spring sowing in cold and warm areas, areas without severe winters, and areas where winters are cold but do not severely damage the crop. Second, as indeterminate, semideterminate, and determinate according to long, short, and zero vegetative growth after the last flower. Faba bean has an effective N2 fixation system by which crops consistently fix high rates of ca. 150 kg N ha− 1. It is grown in a range of rotations, principally with cereals and increasingly in intercrops. Determinate cultivars are used under irrigation (yield target 6 t ha− 1) to avoid excessive vegetative growth, lodging, and suppression of yield by excess biomass. Semideterminate cultivars are replacing indeterminate ones in many rainfed areas, where yield targets are more appropriately 4 t ha− 1. The success of faba bean in Mediterranean environments is due to development and physiological mechanisms by which it avoids, rather than tolerates, water and temperature stresses. The current market for faba bean is dominated by animal feed for which other options are available. The great variability within the domesticated gene pool of faba bean provides options for increasing yield potential through breeding, including determinate cultivars. Faba bean is a partial allogamous species so that partial cross-pollination represents both challenges and opportunities for population development and breeding. To expand autumn sowing in cooler areas, breeding for winter hardiness and frost tolerance can rely on existing genetic variation for these traits. Given the partial allogamy of this species, existing cultivars are either open-pollinated populations or synthetics. Selecting for self‐fertility and developing inbred lines simplifies breeding and seed multiplication but does not take maximum profit of heterosis. The instability of cytoplasmic male sterility systems precludes commercial-scale production of hybrids. Faba bean can be affected by a wide range of biotic stresses, including foliar fungal diseases, soil-borne pathogens, viruses, parasitic weeds, nematodes, and insect pests.