After reading this article you will learn about:- 1. Origin and General Botany of Faba Bean 2. Floral Biology of Faba Bean 3. Breeding Goals 4. Major Breeding Achievements 5. Breeding Scheme and Selection Criteria 6. Variety.
Origin and General Botany of Faba Bean:
The origin of Vicia faba L. is still debated. No wild progenitor has been found, and major differences exist between V. faba and other species belonging to the Narbonensis complex (V narbonensis, V galilea, V. johannis, and V. hyaeniscyamus. Raina and Ogihara (1995) report that In = 12 for Vicia faba and In = 14 for species of the Narbonensis complex. All attempts at interspecific hybridization between Vicia faba L. and these other species have failed.
It is generally accepted that the geographic origin of Vicia faba L. is the Near East and that the subspecies V. faba paucijuga, presently found from Afghanistan to India, is a primitive form. The main characteristics of this ancestor are a short stem, small leaves and seeds (1000-seed weight lower than 250 g) and preferential autogamy. Vicia faba is known to have been cultivated from early Neolithic times.
The evolution of the species accompanied expansion of its cultivation with selection for different sizes and shapes of seeds, various levels of allogamy and differential winter tolerance. Large seeded types (Vicia faba major) with 1000-seed weight greater than 1 kg have developed in South Mediterranean countries and China.
These types expanded in the sixteenth century toward Mexico and South America. Small seeded types with 1000-seed weight less than 500 g (Vicia faba minor) are found in Ethiopian area and have been favoured by North European agriculture. Medium seeded types (Vicia faba equina) have developed throughout Middle east and North Africa with major concentration in Egypt.
The faba bean plant is an annual which requires cool conditions for best development. It is normally planted in the spring in northern latitudes, in the winter in warm-temperature and subtropical areas, but is also a popular crop at higher elevation.
Winter cultivars have 4-6 stems/plant and the spring cultivars have 1-2 stems/plant. The root is typical tap root with secondary roots and nodules due to Rhizobium leguminosarum by vicie. Stem growth is indeterminate. There are leaves up to 5th to 10th node followed by raceme of 2-12 flowers in the leaf axils. There are 2 leaflets/leaf at the bottom and 6-8 leaflets/leaf at the top.
Flowers, 2-3 cm long at anthesis, have a typically papilionaceous structure. They can be completely white, brown or violet. In most cases they concentrate their colour on black or brown melanin spots on the wings.
Pods are short and erected in minor and paucijuga types (3-4 ovules per pod) and long and hanging in major types (8-12 ovules per pod). V. equina types are intermediate having 4 to 8 ovules per pod. Seed colour can be yellow, green, brown, black, or violet and the seed may sometimes carry punctuations, brown spots or stripes around the hilum. The hilum can be black or clear.
Floral Biology of Faba Bean:
Generally, anthers dehisce before the flowers open, but pollen germination is delayed until anthesis. When a frontal visit by an insect occurs, auto or allo-pollen is brought into contact with a disrupted stigmatic surface, and pollen germination and fertilization results.
Auto-fertility defined as fertilization without insect tripping, has been detected in V. faba paucijuga, many winter accessions, and hybrids in general. It has a complex inheritance and seems to be based on several mechanisms among which early production of exudates by stigmatic papillae, large auto-pollen quantity, short style and other floral morphological features are identified.
There are reports suggesting natural out-crossing 2-84% with a mean of 32%. The outcrossing is done by insects/honey-bees. Obligate autogamy has been sought in faba bean by breeding for auto fertility together with closed flower character. Sources of nuclear male sterility are available. The plant breeders have focused on CMS system for hybrid breeding.
Breeding Goals of Faba Bean:
1. High yield
2. Stable yield
3. Desirable seed size and colour as per consumers’ preference of the region
4. High seed protein (current range-27-34% on dry matter basis)
5. High methionine and cysteine
6. Low tannins
7. Low pyrimidine glucosides (vicine and convicine)
10. Resistance to:
i. Chocolate spot (Botrytis fabae)
ii. Ascochyta blight (Ascochyta fabae)
iii. Rust (Uromyces viciae-fabae)
iv. Bean Leaf Roll Virus
v. Bean Yellow Mosaic Virus
11. Tolerance to drought and salt
Major Breeding Achievements of Faba Bean:
Progress in the breeding of Vicia faba results from many individual contributions. These include Darwin’s studies on outcrossing effects, Taylor’s and many other cytogeneticists’ studies on faba bean root tip DNA, and the empirical mass breeding activity of local farmers in the period prior to 1950.
Crisis in world soybean market in 1971, then motivated significant effort at the EEC level culminating in the European Vicia faba multi-locational trials which were conducted under the coordination of D.A. Bond and later P.D. Hebblethwaite.
These trials helped in the definition of adapted genotypes and in the registration on national lists of diverse improved cultivars (short-strawed, stiff-strawed, early-flowering, winter-hardy, Ascochyta and Botrytis resistant, high in protein, zero-tannin, low in vicine-convicine, etc….).
The creation of the International Center for Agriculture in Dry Areas (ICARDA) in 1977 was also a strong support to faba bean research. ICARDA maintains more than 9000 germplasm lines.
With more than 200 characters and their genetic bases described in the third conspectus of genetic variation within Vicia faba, this is the largest world collection and is used by many breeding programs. Other collections with a wide geographical range of accessions are maintained at ZIGuK-Gatersleben/Germany, CNR-Bari/Italy, ETSIA-Cordoba/Spain. INRA- Dijon and Rennes/France.
Molecular knowledge of legumin genes and identification of genetic diversity and genetic linkages with RFLP and PCR markers; have established the steps in the application of molecular biology to Vicia faba breeding. Link (1999) have determined genotypic variation in faba bean for drought tolerance and suggested breeding strategy.
Four sets with 10-19 faba bean genotypes each were evaluated in multi-location field trials between 1992 and 1996. Stress occurred due to natural drought in one experiment and artificial terminal drought in three experiments. Artificial drought was induced by rain shelters; the control treatment was irrigated.
Tolerance was assessed as the ratio of yield under drought (Yd) to well-watered yield (Yw). Highly significant variances between genotypes occurred ; heritability of tolerance was 0.51 < h2 < 0.88. Exotic (North African, Latin American) genotypes were more tolerant than adapted material.
Correlations between Yw and Yd were 0.77** < r < 0.97**, and variance of Yd was less than one-third of the variance of Yw. Drought tolerance was negatively correlated with Yd (-0.41 < r < – 0.22).
Relative reduction of plant height due to drought was a promising trait to improve drought tolerance indirectly in two sets. The prospects of improving Yd are good, heritability was 0.68 < h2 < 0.86. Genetic improvement of drought tolerance also seems feasible. A specific cross was proposed to create improved material.
Breeding Scheme and Selection Criteria of Faba Bean:
The basic scheme of faba bean breeding programs is pedigree selection, the limitation being the inbreeding effect. For this reason many breeders stop this filiation process after the F5 to build population cultivars, or continue up to F7 – F10 to build synthetics or experimental hybrids which will exploit heterosis.
The degree of uniformity required in cultivars by the national registration authority also limits the possibilities for exploiting heterogeneity and heterozygosity.
Due (1997) reviewed many criteria which are of interest to breeders. Table 36.1 summarizes these criteria, the corresponding screening technique, and the stage in the program when they are taken into account according to their heritability and cost. Each additional new criterion used adds to the cost of a breeding program so breeders must consider priorities.
Variety of Faba Bean:
Attractive, dark green pods in clusters, first picking in 65-70 days, green pod yield 180 q/ha.