After reading this article you will learn about: 1. Distribution of French Beans 2. Origin of French Beans 3. Races 4. Qualitative Genetics 5. Breeding Goals 6. Breeding Procedures 7. Plant Genetic Resources 8. Seed Production 9. Marker Assisted Selection 10. Varieties.
Distribution of French Beans:
French-bean (Phaseolus vulgaris L., 2n = 2x = 22) is an important legume crop to be used as green pod vegetable (known by various names as snap bean, string bean, garden bean, fresh bean) or dry seeds (known as dry bean). The dry seed type varieties are called as ‘Rajmash’ in India. Snap bean seed can also be used in dry state like the dry bean types. In that case, pinto, kidney, pink, small red, etc., terms are also used.
In Western World (USA, Western Europe), the fresh pod/processed pod consumption is quite substantial. The world annual production is estimated to be 18 million tons of dry beans and 3 million tons of snap beans compared to 35 million tons of total food legumes. The largest production (> 14 million ha) and consumption of P. vulgaris in the world is of dry beans followed by a much lower production of snap beans.
According to data published by FAO-2006, the world snap bean production in 2006 was 6.3 million tons of which Asia accounted for 72.3%, Europe 15.5%, Africa 8.0%, North America 3.3% and Central America 0.9%. Among leading producers of snap bean have been China, Indonesia, Turkey, India, Egypt, Morocco, Spain, Italy, Belgium, France and USA.
The countries producing substantial dry beans are Brazil, Mexico, Argentina, Chile, Central America and Latin America. In India, green pod as well as dry seed consumption is conspicuous, but figures on area and production are not available. In India, it is primarily grown in Jammu and Kashmir, Himachal Pradesh and hills of Uttaranchal. Production is spreading in plains in Maharashtra, Gujarat, Bihar, Jharkhand and Karnataka.
Origin of French Beans:
The common bean originated in the new world, principally Central and South America. Systematists concerned with the origin of the common bean have disagreed or have been inconsistent in what name should be applied to the closest wild relatives of the domesticated Phaseolus vulgaris L. Phaseolus aborigineus Burk, P. aborigineus var. hundorensis Burk, P. vulgaris forma aborigineus Burk, P. vulgaris ssp. aborigineus Burk are names which have been applied.
In Phaseolus, there are five cultivated species, each with its own ancestor, and about 50 rue wild species. The cultivated species are P. vulgaris (common bean/French bean), P. lunatus (lima bean), P. coccineus (runner bean), P. polyanthus (the year bean) and P. acutifolius (tepary bean).
During the process of domestication in common bean, several morphological changes have occurred. The cultivated French bean is an erect growing plant with determinate branching, whereas the wild type is indeterminate and profusely branched. The cultivated types have smaller number of nodes on the main axis, while the wild forms have more nodes. The internode length 5 relatively shorter in the cultivated types.
The changes under domestication are typically loss of seed dormancy and pod dehiscence mechanism, a change from perennial to the annual life form and a great change in seed size correlated with modified shoot architecture. Stems tend to be thicker, leaves larger, branches fewer, the number of nodes may be reduced and internode length is shortened.
This process culminates in evolution of self-supporting plants well adapted to mono-crop husbandry systems. This has also led to appearance of a vast variety of seed sizes, shapes and colour and selection for photoperiod insensitivity.
Races of French Bean:
The details have been provided by Singh (1991).
A brief description is as follows:
Middle American Races:
Mesoamerica:
This race includes small-seeded (< 25 g/100 seed) landraces of all seed colours and growth habits. The group is often characterised by an ovate, cordate or hastate terminal leaflet of trifoliate leaves and large, broad cordate or lanceolate bracteoles. Inflorescences are multinoded. Pods are 8-15 cm long, slender, fibrous or parchmented and easy to thresh. This race is distributed throughout the tropical low lands and intermediate altitudes of Mexico, Central America, Colombia, Venezuela and Brazil.
Durango:
These are predominantly of indeterminate, prostrate growth habit III, which is characterized by relatively small to medium ovate or cordate leaflets, thin stems and branches, short internodes, and fruiting commencing from and concentrated in basal nodes.
These landraces often possess small ovate bracteoles with a pointed tip. The pods are medium sized (5-8 cm), flattened with 4-5 flattened rhombohedric seeds of medium size (25-40 g/100 seeds). This race is distributed in semiarid central and northern highlands of Mexico and Southwestern USA.
Jalisco:
This race is often characterized by indeterminate growth habit IV. Plant height can be over 3 m in its natural habitat. The terminal leaflet of trifoliolate leaves is hastate, ovate, or rhombohedric and sometimes relatively large. Stems and branches are weak and have medium-sized or long internodes.
Most germplasm from this race possesses medium-sized, cordate, ovate, or lanceolate bracteoles. Fruiting is distributed either along the entire length of the plant or mostly in its upper part. Pods are 8-15 cm long and have five to eight medium-sized seeds, whose shape is round, oval, or slightly elongated and cylindrical or kidney-shaped. Their natural habitat is the humid highlands of central Mexico and Guatemala, where maximum diversity is found.
South American Races:
Nueva Granada:
Germplasm is mostly of growth habits I, II, and III with medium (25-40 g/100 seeds) and large seeds (< 40 g/100 seeds) of often kidney or cylindrical shapes which vary greatly in colour. Leaves are often large with hastate, ovate, or rhombohedric central trifoliolate leaflets and long, dense, straight hairs. Stem internodes are intermediate to long.
Bracteoles are small or medium, and ovate, lanceolate, or triangular. Dry pods are fibrous, hard, medium to long (10-20 cm), and leathery, and possess four to six seeds. The pod beak often originates between the placental and ventral sutures.
This race is distributed mostly at intermediate altitudes (< 2000 m) of the northern Andes in Colombia, Ecuador, and Peru, but it is also found in Argentina, Belize, Bolivia, Brazil, Chile, Panama, and some Caribbean countries, including the Dominican Republic, Haiti, and Cuba.
Chile:
Landraces are predominantly of indeterminate growth habit III. These are characterised by relatively small or medium hastate, rhombohedric, or ovate leaves; short internodes; small or medium, and narrowly triangular, spatulate, or ovate bracteoles; light pinkish or white flower; medium-sized (5-8 cm) pods, often with reduced fibre content; and round to oval seeds (three to five per pod).
Morphologically, these landraces largely resemble germplasm from race Durango, except that seeds of race Chile are round or oval, and fruiting is more sparse. In some of the landraces (e.g., ‘Coscorron’ (G 4474) and ‘Frutilla’ (G 5852), pods exhibit an attractive anthocyanin striping, and in many countries these are harvested for green seeds (green shelled or “granados”) before physiological maturity. This race is distributed in relatively drier regions at lower altitudes in the southern Andes (southern Peru, Bolivia, Chile, and Argentina).
Peru:
Key morphological characteristics of germplasm belonging to this race are the large hastate or lanceolate leaves (often basal) and long and weak internodes with either indeterminate or determinate type IV climbing growth habit. In its natural habitat, it is always grown in association with maize and other crops. Pods are often long (10-20 cm) and leathery.
Fruiting is distributed either along the entire stem length or only in the upper part of the plants. Seeds are large and often round or oval but can also be elongated. This group is highly photoperiod sensitive and is adapted to moderately wet and cool temperatures often requiring more than 250 days to maturity. The race is distributed from the northern Colombian highlands (>2000 m) to Argentina.
Varietal Groups on the Basis of Growth Habit and Plant Architecture:
Determinate Bush Habit:
1. Few nodded bush or dwarf types 3-7 trifoliate leaves on the main stem before terminal double raceme-early types in Europe and USA.
2. Many nodded types – 7-15 or 15-25 trifoliate leaves on the main stem of middle American or Andean origin respectively, with some climbing ability-Growth habit 1.
Indeterminate Habit:
1. Growth Habit II-Indeterminate, upright bush, erect stem, often without a guide.
2. Growth Habit III-Indeterminate prostrate with low or non-existing climbing ability.
3. Growth Habit IV-Indeterminate with long guide and high climbing ability.
Varietal Groups Based on Pod and Seed Characteristics:
1. Green bean
2. Wax bean (Yellow pods)
3. Romano/Italian/Flat podden bean
4. Round podden bean
According to Colour:
1. Green
2. Yellow (wax)
3. Purple
4. Multi coloured
5. Dark green (Blue Lake type)
Based on Fibres:
1. String bean – enough fibrous strands in each suture of pod, which had to be removed manually before cooking.
2. String-less bean-A single dominant gene prevents string formation.
Seed Shape:
1. Round
2. Round to elliptic
3. Elliptic
4. Kidney-shaped
Seed Coat Colour:
1. Black
2. White
3. Green
4. Grey
5. Yellow
6. Buff
7. Red
8. Violet
Varietal Groups Based on Mode of Consumption:
1. Horticultural beans – Consumed as fresh/processed, fibreless immature pods.
2. Green shell or fresh grain beans-consumed as fresh, full-sized seed.
Snap Beans:
1. Home garden types-Cover a wide range of pod sizes, shapes, colours, flavours, determinate bush to indeterminate types.
2. Fresh market types-Grown close to market, cover a wide range of types.
3. Shipper types-Appear fresh-looking after several days in transit.
4. Processing/freezing types-Fresh market types with light to medium green colour, e.g., Tender crop.
Qualitative Genetics of French Beans:
An exhaustive list of about 150 genes of Phaseolus has been compiled by Yarnell (1965). A few important genes from that list as summarised by Ram and Singh (1994) are given in Table 16.1.
There are at-least 8 genes controlling seed colour and one P is basic to coloured seeds so that all white seeded forms are homozygous recessive pp and breed true. Black seed is epistatic to all other colours.
Breeding Goals of French Beans:
1. High pod yield
2. Non-stringy, long pods, flat or round in shape
3. Early pod harvesting
4. Bush/pole plant type
5. High number of green pods/plant
6. High number of pod clusters/plant
7. High number of primary branches/plant
8. Free from inter-locular space
9. Abiotic stress tolerance (high and low temperature, drought, salinity, soil nutrient deficiency, N.fixation)
Resistance to diseases:
1. Bacterial brown spot (Pseudomonas syringae pv. syringae (Van Hall)
2. Bacterial wilt (Corynebacterium flacumfaciens pv. flacumfaciens (Hedges)
3. Common blight (Xenthomonas campestris pv. phaseoli)
4. Halo blight (Pseudomonas ryringae pv. phaseolicola (Burk) Dows
5. Alternaria leaf spot (Alternaria alternate)
6. Angular leaf spot (Isariopsis griseola)
7. Anthrocnose (Colletotrichum lindemuthianum)
8. Ascochyta leaf and pod spot (Ascochyta boltshauseri Sacc. and A. phaseolorum Sacc.)
9. Rust (Uromyces phaseoli)
10. White mould (Sclerotinia sclerotiorum)
11. Fusarium root rot (Fusarium solani f.s.p. phaseoli)
12. Rhizoctonia root rot (Rhizoctonia solani)
13. Bean Common Mosaic Virus (BCMV)
14. Beet Curly Top Virus (BCTV)
15. Bean Golden Mosaic Virus (BGMV).
Breeding Procedures of French Beans:
French bean is an autogamous crop and breeding procedures applicable to such crops are generally applicable to this. Pedigree selection is effective for such characters as height, maturity and disease resistance. However, single plant selection for yield in early generations has not been encouraging.
In this situation, the use of bulk-breeding is often suggested. Results often suggest that bulk-breeding does not lead to the elimination of high yielding genotypes. Therefore, bulk- breeding would appear to be a better use of resources, when selecting for seed yield. The populations are bulk-bred until F5 and then individual plant progenies are evaluated in replicated yield trials.
A procedure of gamete selection as suggested by Singh et al. (1998) and followed at CIAT, Cali, Colombia is given Fig. 16.1. Gamete selection is a selection based on F1 derived families that come from crosses that are multiple-parent, heterogeneous and heterogametic.
In bean breeding, the contributions of Anderson, Frazier Parker, Pierce, Zaumeyer, Silbernagel, Shree Pal Singh and Gepts deserve special mention and appreciation.
Disease Resistance:
There are nearly 30 major diseases of beans and the more important ones are listed in Table 16.2.
Sources of resistance to various diseases based on the information compiled by Schuster and Coyne (1981), Ockendon (1983), Silbernagel (1986), Nene (1988) and Sharma and Joshi (1993) are listed in Table 16.3.
At Pantnagar which is a ‘hot spot’ for several diseases, Pant Anupama and Pant Bean 2 (released varieties) have been found to be moderately resistant to bean common mosaic virus and rust.
To screen for multiple disease resistance, workers have used infected crop debris, planted spreader rows of susceptible cultivars, and depended on high natural incidence. For soil-borne diseases, a permanent disease nursery (sick plot) is used. Detailed screening techniques have been described by Schuster and Coyne (1981) and Silbernagel (1986).
It may, however, be emphasised that considerations of time, space, expense, and the requirements for large numbers often dictate that screening be done under field conditions. However, for confirmation of resistance with identified pathogen, controlled greenhouse or growth chamber conditions are needed.
It is therefore, suggested that screening for resistance should normally be carried out in the field preferably under ‘hot spot’ conditions, and laboratory and glasshouse procedures should be developed as a supplement to field screening.
From genetics point of view, resistance to BCMV is controlled by the dominant gene I originally found in the cv Corbett Refugee. Race specific additional genes bc 1, bc 2 or bc 3 have been identified and one of these genes should be combined with I gene to have broad resistance to both the necrotic and mosaic mottle reactions.
For fungal diseases, a variety Cornell 49/242 has been reported to have the dominant gene ‘Are’ for resistance to anthracnose. This resistance has been overcome by new races and new genes Mex 2 and Mex 3 will have to be combined with ‘Are’ gene to have more stable polygenic resistance.
One of the most widespread and severe diseases of common bean is angular leaf spot caused by Phaeoisariopsis griseola (Sacc.) Ferr. The fungus infects most aerial parts of the plant, especially pods, seeds, leaf petioles and lower surfaces of leaflets causing premature leaf drop, foliar and stem necrosis that culminate in poorly filled seeds and reduced seed quality. The screening under field experiments and laboratory are as follows.
Each genotype is sown in 2 m rows that are 0.6 m apart, with 30 plants per row. The controls known for their reaction to angular leaf spot are distributed every 20 rows. All common bean accessions and check cultivars are inoculated with a mixture of isolates of races of P. griseola originally isolated from the site.
Plants are inoculated four times starting 21 days after planting when most of the plants are in the second or third trifoliolate leaf stage, and thereafter, at weekly intervals, to ensure high and uniform levels of ALS infection. Inoculations consist of spraying with an aqueous suspension of P. griseola spores suspended in tap water to a final concentration of 2x 104 spores mL-1.
Plants are inoculated after sunset to benefit from the darkness and high relative humidity at night. Disease evaluations start 14 days after the first inoculation and continue till maturity, using a CIAT 1-9 scale described as follows: 1, plants with no symptoms; 3, plants with 5-10% of the leaf area with lesions; 5, plants with 20% of the leaf area with lesions and sporulation; 7, plants with up to 60% of the leaf area with lesions and sporulation, associated with chlorosis and necrosis; 9, 90% of the leaf area with lesions, frequently associated with early loss of the leaves and plant death.
Genotypes that have a score of 3 or less are considered resistant, 4-6, intermediate and a score greater than 6 are considered susceptible. All susceptible accessions are discarded. Accessions with resistant or intermediate reaction are reevaluated in replicated plots in subsequent cropping seasons, using the same procedures.
To estimate the usefulness of the potential sources of ALS resistance, wild accessions that display resistance in the field are further studied in the greenhouse using the same and other P. griseola races. Nine plants of each accession are sown in three pots, three plants per pot and inoculated with a spore suspension 1 X104 spores mL-1.
Plants are inoculated when the first trifoliolate leaf is fully expanded. Inoculated plants are placed in a humid chamber at approximately 22°C and relative humidity >95%, with a 12 h light/dark cycle. After four days in the humid chamber, plants are put on tables in the greenhouse and the temperature maintained between 24-30°C.
Plants are scored three times, starting 8 days after inoculation using the scale described previously.
The common bean accessions, available at CIAT, Cali, Colombia and resistant to Andean and Mesoamerican races of P. griseola under field conditions in Colombia are as follows:
Root rots caused by Fusarium solani, Rhizoctonia solani and Pythium spp. cause considerable yield losses. Generally, there is linkage between black seed coat colour and resistance to Pythium.
However, it has been possible to introduce resistance to Pythium ultimum Trow from a black- seeded variety into a white seeded line, thus breaking the association between seed coat colour and Pythium resistance. Resistance to Fusarium root rot has been due to several quantitative genes and is independent of resistance to thielaviopsis and pythium root rots.
Breeding for root rot resistance has been found to be difficult because of:
(i) Lack of high levels of stable resistance in horticulturally acceptable plant and pod types
(ii) General association of coloured seed coat and late maturity with resistance
(iii) Lack of clarity as to the genetics of resistance (which generally has a low degree of heritability) or the nature of resistance
(iv) Lack of reliable screening techniques
White mould is another fungal disease which causes considerable yield damage in India in the winter crop particularly during rains. The disease is more severe in fields with a previous history of white mould which often have a high density of sclerotia.
Wet weather promotes the production of apothecia. Ascospores discharged from the apothecia are responsible for primary infection. Secondary spread is achieved by plant to plant mycelial growth.
Secondary spread can be rapid in wet, warm weather. Ex Rico 23 a cultivar of white bean introduced into Canada from Colombia has shown tolerance to white mould. Plant architecture which allows a drier, warmer microclimate under the canopy, suffers less by white mould.
Miklas and Delorme (2003) reported QTL conditioning resistance to white mould in snap bean. According to them host resistance is an important component of integrated disease management strategies for control of Sclerotinia white mould disease in snap bean. Few resistant snap bean cultivars have been bred, however, genetic resistance to white mould is not well understood.
These authors examined inheritance and identified quantitative trait loci (QTL) for white mould resistance in an F5.7 recombinant inbred line (RIL) population (‘Benton’/NY6020-4). ‘Benton’ snap bean is susceptible to white mould. Snap bean germplasm line NY6020-4 has partial resistance.
The parents and 77 F5.7 RILs were tested for resistance to white mould across four greenhouse and two field environments. Moderately high heritability estimates were observed for straw test (0.73) and field (0.62) reaction. Selective mapping of 27 random amplified polymorphic DNA (RAPD) markers detected two QTL conditioning resistance to white mould on linkage groups B6 and B8 of the core map.
The B6 QTL explained 12% and B8 QTL 38% of the variation for disease reaction in the straw test. The two QTLs explained 13% and 26% disease reaction in the field, respectively. Favourable alleles for all the QTLs were derived from NY 6020-4, except for the B6 QTL conditioning resistance to white mould in the field, which was derived from ‘Benton’.
The B6 QTL was located near the Ur-4 rust resistance gene, and was associated with canopy height and lodging traits that condition disease avoidance. The B8 QTL was associated with increased internode length, an undesirable trait in snap bean, which may hamper use of white mould resistance derived from NY 6020-4.
Genetics and breeding of bacterial diseases are as follows:
Several patterns of qualitative genetic control and effect of genetic background have been reported for halo blight. Common blight is inherited quantitatively, with low heritability. For bacterial wilt, success has been realised in developing lines and cultivars of dry beans with high tolerance to Xp, Xpf and Cf using pedigree method of breeding.
Insect Resistance:
For insect resistance, the information is meagre and cultivars with identified resistance are not known. Pawar et al. (1987) evaluated 11 strains of French bean for resistance to stemfly (Ophiomya phaseoli) and found that cultivars Sel. 2, UPF 191 (now released as Pant Anupama), SVM 1, Sel. 9 and Sel. 4 had significantly lower agromyzid population than VL Boni 1, Sel. 5, Pusa Parvati and Contender.
Environmental Stress Tolerance:
Important environmental stresses for French bean are drought, heat and cold. Drought tolerance is often associated with a well-developed root system. Sensitivity of cultivars to high temperature (> 35°C) is reflected in reduced pollen production and/or viability. Heat tolerance is associated with the ability of pollen tubes to grow at high temperatures, allowing pod setting under these conditions.
A breeding line 5 BP 7 has been reported to be heat tolerant. There is a need to develop varieties which are able to grow more vigorously and reach flowering earlier under low temperature conditions. The characters contributing towards cold tolerance are large embryonic axis, rapid hypocotyl elongation, rapid mobilization of cotyledonary reserves, leaf area, and production of surplus photosynthate.
Yield Improvement:
In French bean, the yield components are the number of pods, the number of seeds/pod and seed weight. Number of pods/plants and seed weight are negatively correlated, i.e. there is yield component compensation effect between yield components, creating difficulty for yield improvement.
Davis and Evans (1977) demonstrated that selection indices for P. vulgaris which included the yield components were less efficient than those which included plant type characteristics particularly, total node number, inflorescence number and hypocotyl diameter.
In the second order yield components, leaf number is associated with pod number and leaf size with seed size. However, like the first order yield components, leaf number and size are negatively correlated.
In this contrasting situation of ‘size characters’ vs. ‘number characters’, ‘size characters’, e.g., raceme internode length, leaf size, hypocotyl diameter, basal internode length, average internode length, long internode length, pod length and pod distribution appear to have some yield advantage.
The concept of ideotypes has, since its formal introduction by Donald (1968) received mixed views as mentioned by Acquash et al. (1991). Coyne (1980) argued that information on relative merits and contribution of physiological yield components and morphological traits was insufficient to warrant such an approach to crop breeding.
Blixt and Vose (1984) observed that plant models are traditionally viewed from a phenotypic perspective, without considering the fact that morphology is derived from the expression of biochemical and physiological processes.
Theoretically, the consideration of an ideo-type from the genetic perspective is more meaningful because new re-combinations that emerge cannot be predicted by adding the phenotypic effects, but only by knowing the allele-environment interactions.
Rasmusson (1987) stated that breeders should be concerned not only with morphological traits, but also with physiological, biochemical, anatomical, and phenological traits, because these traits are interrelated or inter-dependent. This implies that in designing plant ideotypes, objectives should be set specifically, for both physiological processes and morphological structures.
It appears more progress would be made with ideo-type breeding if processes that determine morphology were better understood. However, it has been observed that little progress in the use of physiological and biochemical selection criteria for yield improvement has been achieved.
Adams (1982) proposed and developed an erect bean ideo-type suitable for mechanised farming in the humid Midwest (USA). The ideo-type was described as an architype because it emphasised specific architectural features of the plant.
These features include from three to five upright basal branches, a thick hypocotyl, narrow plant profile, high values of first order yield components and plant height between 50 and 55 cm, with main stem nodes numbering 12-15, upper internodes longer and more vigorous than basal ones, and a leaf area index (LAI) of 4 at flowering.
The architype also has a Type II growth habit (indeterminate with short terminal vine). Acquash et al. (1991) conducted an investigation to determine the substantive indicator of erect plant architecture in dry bean. A stepwise multiple regression procedure was used to determine traits that are effective indicators of erect plant architecture.
Hypocotyl diameter, plant height, branch angle, and pods on main stem and, especially in the midsection were selected for inclusion in the regression model, suggesting their important contributory role in dry bean ideo-type. Dry bean breeders should emphasise these four traits for effective selection and efficiency in a breeding programme for erect plant architecture.
Plant Genetic Resources of French Beans:
International Centre for Tropical Agriculture (CIAT), Cali, Colombia has the mandate for global germplasm collection and conservation of Phaseolus beans. The status of bean collections held at the CIAT Genetic Resources Unit, Colombia is given in Table 16.4.
CIAT, Cali, Colombia has mandate to conserve over 30,000 accessions of domesticated and wild beans, as well as newer collections made in collaboration with International Board for Plant Genetic Resources (IBPGR) now International Plant Genetic Resources Institute (IPGRI). The IPGRI database contains passport data of over 30000 accessions representing the Phaseolus collections maintained in European gene-banks (www(dot)gene bank(dot)at/phaseolus).
These accessions are maintained under two types of storage:
Short-medium term storage at 5° C-working collections.
Long term storage sealed in laminated bags at 5-8% seed moisture and stored at -20° C.
In India, French-bean germplasms are conserved at NBPGR-Regional Station, Bhowali Uttarakhand and Regional Station, Shimla.
Seed Production of French Beans:
For nucleus seed production, several hundred single plant selections are made and are planted as single-row plant progenies next year. Each row is checked carefully for off types and all the doubtful progenies are totally discarded. The harvest from the remaining progenies is bulked and this bulk-produce is known as nucleus seed which is used to produce breeder seed.
Breeder seed gives rise to foundation seed, and foundation seed is used to produce certified seed. The most common off types are flat or oval podded and stringy podded rogues which are the cause of greatest number of customer complaints.
The genes governing pod shape and pod feature (fibres) appear to be less stable and have a higher reversion rate. These need to be removed rigorously during seed plot monitoring. Seed lots of most snap beans need to be replaced every 3-5 years to keep the frequency of flat podded and string podded mutants within acceptable limits.
Isolation Distance:
Breeder/foundation seed – 50 m
Certified seed – 25 m
The higher isolation distances are basically to avoid admixture otherwise 3 m distance is adequate.
Roguing Stages:
1. Before flowering
2. At start of flowering
3. At seed set and first pod formation
Seed Yield:
1. Seed yield-1500 – 2000 kg/ha
2. 1000 seed weight – 250 – 600 g
Marker Assisted Selection of French Beans:
MAS adds speed and precision to the on-going conventional plant breeding programmes. Selection decision in a crop breeding programme can be based on phenotypic information, molecular information or a combination of both. However, at the end of the selection cycle based on phenotyping or genotyping or a combination of both, the final evaluation of the product has to be done on the basis of phenotypic performance at multi-locations/environments.
A random amplified polymorphic DNA marker directly linked with bean curly top virus has been reported. Larsen and Miklas (2003) reported that SCAR would be useful as MAS for bean curly top virus resistance in snap bean. In addition, a major gene for resistance to anthracnose, and QTL for resistance to common bacterial blight, white mould, and ashy stem blight mapped in the same region of the also chromosome B7.
Bct is located about 25 cM from P Locus that conditions seed coat colour and recessive gene p gives white seed colour. RAPD markers linked to gene for 5 classical marker traits, namely, dark green savoy leaf (dgs), blue flower (blu), silvery green pod (arg), yellow wax pod (y) and flat pod (a spontaneous mutation from round to flat pod in Hialeah snap bean) can be integrated to form a more complete and informative genetic linkage map as compiled and narrated by Koutsika-Sotiriou and Traka-Mavrona (2008). RAPD markers have been used in common beans. RAPD markers linked to disease resistance genes in common bean are given in Table 16.5.
Varieties of French Beans:
Bush Types:
Contender:
This is an introduction from USA. Plants are bush type and dwarf. Flowers are pink. Pods are round, green, about 15 cm long, non-stringy, meaty and slightly curved. Seeds are light brown. First green pod picking can be had in 50 – 55 days after sowing. It is susceptible to bean common mosaic virus. Green pod yield potential is about 80 q/ha. It has been recommended by IARI, New Delhi and is very old variety.
Pusa Parvati:
This variety has been developed as a mutant at IARI Regional Research Station, Katrain from irradiation of a yellow podded line EC 1906. The plants are bush type, early, taking about 50 days for first green pod picking. Pods are long (15 – 18 cm), straight, flattish round, string-less and green in colour. Green pod yield potential is 80 q/ha. It is susceptible to viral diseases.
VL Boni 1:
This variety has been developed as a selection from germplasm at Vivekanand Parvatiya Krishi Anusandhanshala, Almora. Plants are dwarf (40 cm). It was identified for release by 1985 vegetable workshop for the northern hilly regions. Flowers are white and purple tinged.
The pods are medium long (12 cm), round, fleshy, non-stringy with pale green colour. Pods are ready for harvesting in about 55 says. It can be planted in the hills from March to July. It is susceptible to viral diseases. The yield of green pods is about 80 q/ha.
Arkal Komal:
It is an Australian introduction by IIHR, Bangalore, accessioned as IIHR 60. It was identified by 1987 vegetable workshop for northern hills, semi-arid Lava plateau, central highlands and humid to semi-arid western Ghats and Karnataka plateau. Plants are erect and bushy. Pods are straight, flat, tender, green and suitable for transport. First green pod picking takes 65-70 days. The green pod yield potential is about 100 q/ha.
Pant Anupama:
This was obtained through selection in germplasm lines maintained at GBPUAT, Pantnagar. The line was evaluated as UPF 191 in the coordinated trials. The plants are dwarf with dark green foliage. It is a prolific bearer with smooth, tender, non-stringy, medium long, round, straight, translucent, and green pods concentrated at mid-height. The pods are below the canopy and thus, remain protected from sun light.
The pods are so tender and fibreless that these could be eaten as such as salad also. The seeds are dark brown. It was released by the U.P. state variety release committee in 1983 followed by its notification in 1984 by the central variety release committee.
It was formally identified by the vegetable workshop in 1987. First picking is done in 55-65 days. The yield potential is 90 q/ha. It is moderately resistant to bean common mosaic virus and resistant to rust.
Pant Bean 2 (UPF 626):
This variety was developed at GBPUAT, Pantnagar through pedigree method of breeding from a cross of Turkish Brown x Contender. It was released by the U.P. state variety release committee in 1995 and was notified by the central variety release committee in 1996. The plants are bush type and sturdy. The pods are flattish round, straight and non-stringy at edible stage. The seeds are brown with mottling and are bold.
Thus, this variety is dual purpose i.e. vegetable type as well as dry seed type (Rajmash). First green pod picking is done in about 60 days after sowing. The yield potential is 90 q/ha, green pods. It is moderately resistant to bean common mosaic virus and resistant to rust.
Arka Suvidha:
Bush type, high yielding, multiple disease resistant variety developed by IIHR, Bangalore has been registered by PPV FR and A, GOI.
Pole Types:
Kentucky Wonder:
It is an introduction from USA. The plants are tall, pole type and have creeping/viny habit. Green pods are ready for harvesting in 60 – 65 days. There are 4 – 5 pods/cluster. Pods are long (20 cm), flattish, meaty, string-less. Seeds are light brown. Green pod yield potential is 100-125 q/ha.
Canadian Wonder:
This is a white seeded cultivar. Plants are climbing type and need staking. Pods are straight, round, non-stringy, fleshy, green, about 10-12 cm long. Pods are in clusters of 4-5 pods. The variety is high yielding and widely adapted.