In the recent past, Snap bean has been an important crop in ensuring food security and economic stability.Research towards improving the crop is therefore timely.

1. SNAP BEAN BREEDING IN EASTERN
AFRICA
KENNETH TEMBE ODUOR
A56/69956/2013
MSC. AGRONOMY
DEC 2013

2. CONTENT
1. INTODUCTION
2. ORIGIN AND CYTOGENETICS
3. REPRODUCTIVE SYSTEMS
4. BREEDING OBJECTIVES
5. BREEDING METHODS
6. WORK DONE IN EASTERN AFRICA, MAJOR
ACHIEVEMENTS AND LESSONS LEARNT
7. CONCLUSIONS AND FURTHER WORK
8. LIST OF REFERENCES

3. INTRODUCTION
• Green bean is the immature green pod of the
P.vulgare primarily grown for export .
• major export vegetable commodity in Eastern Africa
with the main producing countries being Kenya,
Tanzania, Uganda and more recently Rwanda. Kenya
exported about 44 thousand metric tonnes of snap
beans in 2012 valued at about KES 1.7 billion. (HCDA
2012)
• estimated that over 90% of the crop produced in
Eastern Africa is exported to regional and global
markets (CIAT 2006).
• grown by both small- and large-scale farmers in
Eastern Africa for fresh and processing markets (KARI
2004).

4. cont’ introduction
• Compared to dry beans, snap beans have a high
market value, mature much earlier and have a longer
harvest duration (Ugen et al. 2005)
• snap beans with quality characteristics demanded by
target markets is vital to increasing consumption and
export value (Ndegwa et al. 1999; Muchui et al. 2006;
Ndegwa et al. 2008; Kimani et al. 2009;).
• high seed costs, lack of high yielding pest and disease
resistant commercial snap bean varieties is perhaps
the most critical constraint to snap bean production
(Kimani et al. 2004).

5. cont’ introduction
• snap beans grown in Eastern Africa were developed in
temperate regions particularly North America and Europe
and are therefore not well adapted to biotic and
environmental conditions in Kenya and other countries in
Eastern Africa.
• foreign varieties are very susceptible to bean rust, angular
leaf spot, root rots and bean common mosaic virus among
other diseases and pests, especially bean stem maggot,
thrips, spiny bugs, pod bores, bean aphids, red spider mites
and white flies (Nderitu et al. 1996; Kimani et al. 2004)
• to depend on very expensive fungicides and insecticides to
reduce production and post-harvest losses associated with
disease and pests. However, this option is not viable
because of the recently instituted maximum residual limits
(CIAT 2006)

6. ORIGIN AND CYTOGENETICS
• Domesticated in central and south America more than
6000years ago. Mexico and Guatemala, and Peru and
neighbouring countries
• Dry seeds were introduced and planted in Spain during
the 16th
C . It was taken to France. The unripe pods soon
became popular as a vegetable in Europe.
• use of the green pods was made possible by a
considerable reduction of ‘parchment’ consisting of
cross-intersecting fibres in the fruit wall.
• This character, polygenic in heredity, was improved by
breeding in Europe during the 18th
and 19th
centuries.
• hard fibres along both satures (strings) were first
eliminated by a dominant mutation, which appeared
spontaneously during the 19th

7. Cont’ orgn and cytgn
• Presently French beans is produced all over
the world and can be found in all countries of
tropical Africa.
• Popular in Francophone than Anglophone
countries, more in urban than in rural areas,
more in highlands than lowland regions, and
more during the cool season than during the
hot season.
• Snap bean just like other bean varieties have
a chromosome number of 2n=22

8. REPRODUCTIVE STRUCTURE
• The Inflorescence forms an axillary or terminal
raceme up to 15(–35) cm long,
• Flowers are bisexual, hence snap bean is
autogamous in nature.
• corolla is white to pale purple or red-purple,
hood-shaped, of about 1.5 cm long, wings ;
• has 10 stamens , 9 fused and 1 free;The
ovary is superior and laterally compressed.

9. SNAP BEAN BREEDING OBJECTIVES IN
EASTERN AFRICA (CIAT 2006)
• Regional snap bean programme supported in
2006 by ASARECA, was initiated to develop
improved snap bean varieties with :
 high yield potential,
 resistant to biotic stresses, and
 high pod quality for smallholder producers .

10. objectives of the snap bean breeding
in Kenya (Kimani 2010):
1. To select bush snap beans with multiple resistances
to rust, angular leaf spot and anthracnose.
2. To evaluate advanced bush snap bean lines for pod
quality, marketability, shelf life and high
productivity, and resistance to aphids, thrips and
bean stem maggot.
3. To select climbing snap bean lines with multiple
resistances to rust, angular leaf spot and
anthracnose.
4. To evaluate advanced snap climbing bean lines for
pod quality, marketability, shelf lifeand high
productivity and resistance to nematodes and root
rots

11. BREEDING METHODOLOGY IN SNAP
BEAN
• pedigree method- developing new snap bean
cultivars -effective for traits with moderate to
high heritabilities
• The disadvantage is that by selecting traits
with high heritability in early generations,
genetic variation with low heritability is lost
(Fouilloux and Bannerot, 1988).

12. Cont’ breeding method
• single seed descent and bulk breeding methods
(Fouilloux and Bannerot, 1988) - more efficient
for cultivar development than pedigree in
preserving genetic variation with low heritability
• Bulk breeding is more efficient than single seed
descent when labour costs and land use were
considered (Fouilloux and Bannerot, 1988). Single
seed descent allows genetic analysis of traits in a
population whereas bulk breeding does not.
• Recurrent backcrossing has also been used as a
standard procedure for the introgression of
qualitative traits into an elite background.
Silbernagel (1986)

13. Cont’ breeding method
 lack of recombination in snap bean may be part of the
bottleneck to trait transfer. Common bean chromosomes
are small with an average of less than two chiasmata per
bivalent (Marechal, 1971).
 The low rate of crossing over limits the amount of
recombination that can occur in any one reproductive
cycle.
 determine why quite often in a cross between two
separate bean types, types that resemble the parents are
recovered in high frequency, with very few that show
intermediate or recombinant characters.
 breeding methods, such as recurrent selection, and
congruity backcrossing and inbred-backcross method can
give more opportunities for recombination (Urrea and
Singh, 1995; Anderson et al., 1996; Wehrhahn and Allard,
1965; Bliss, 1981).

14. Cont’ breeding method
• The use of molecular markers may help facilitate the transfer of
traits from an unadapted background into snap beans.
• Two approaches are conceivable. The conventional approach would
be to use molecular markers to tag genes or QTL of interest such
has been done for several traits in bean (Adam-Blondon et al.,
1994a; Alzate-Marin et al., 1997a, 1997b)
• Many of these markers for disease resistance have been of interest
to some snap bean breeding programs
• The tags would facilitate introgression of the trait of interest during
some recurrent crossing procedure (such as backcrossing)
• The advanced backcross QTL analysis proposed by Tanksley and
Nelson (1996) may be a useful method for introgressing genes from
a dry bean into a snap bean background, particularly where
molecular markers for a trait are unknown

15. Cont’ breeding method
• Molecular maps that have been developed for bean (Adam-
Blondon, et al., 1994b; Nodari et al., 1992, 1993a, 1993b;
Skroch et al., 1996; Vallejos et al., 1992) have significantly
facilitated breeding of snap .
• With the number of RFLP, AFLP, and RAPD markers known,
it should be possible to develop a set of polymorphic PCR-
based markers to tag a snap bean cultivar’s genome, a
process described as Whole Genome Selection (Tanksley
and Rick, 1980).
• A marker would be placed on each chromosome arm.
From segregating cross progeny, selection for individuals
with the most complete set of markers and the trait of
interest should result in the recovery of progeny with most
of the snap bean traits intact and with the novel trait of
interest as well.

16. WORK DONE IN EASTERN AFRICA
• Work at Kawanda (Uganda) focused on screening snap
bean varieties with farmers and developing production
packages. Three lines were selected after four years of
evaluation with farmers. These are HAB 433, J12 and
L3.
• Moi University, Kenya aimed at developing locally
adapted snap bean cultivars with improved pod yield,
resistance to anthracnose and rust, and marketable
pod quality. Four lines were rated resistant to rust,
• had good pod quality, comparable to that of
commercial cultivars
•

17. Cont’ work done in E.A
• At KARI-Thika focused on developing a working
collection of snap and runner bean varieties, and on
developing segregating populations
• Twenty F4 selections from a cross between a
commercial variety and a locally improved rust
resistant variety (‘Kutuless’) were made. Two
promising F4 lines showed a type 1 growth habit, good
ground-pod clearance, high pod load (30-40
pods/plant), acceptable pod characteristics and good
snapping ability.
• At the University of Nairobi, crosses were made to
transfer rust resistance to three susceptible snap bean
varieties

18. Cont’ work done in E.A
• Availability of public commercial varieties which
will increase access to seed by smallholder
• likely to lower production costs due to improved
access to seed and
• reduced reliance on fungicides in the region and
pesticides-farmers to meet stringent export
requirements for residue levels, essential if this
crop is to continue providing incomes and
employment in rural areas.

19. FURTHER WORK
• With much of the world bean germplasm
adapted to the tropics, problems with daylength-
sensitivity, and adaptation to specific
temperature regimes can obscure performance
at the higher latitudes. One solution to this
problem is to convert daylength-sensitive
material to daylength insensitivity.
• A process has been initiated to convert tropical
dry bean lines .
• A similar process should be used with tropically
adapted snap bean lines.

20. CONCLUSION
• Breeding activities in snap beans in the region
have been successful.
• Varieties developed are:
 high yield potential,
 resistant to biotic stresses, and
 high pod quality for smallholder producers

21. REFERENCES
• Kimani PM, van Rheenen HA, Mathenge P, Ndegwa A. 2004.
Breeding snap bean for smallholderproduction in East and Central
Africa. Annual Report 2004. CIAT, Cali, Colombia. p 49–51.
• CIAT [International Center for Tropical Agriculture]. 2006. Snap
beans for income generation by Fouilloux, G. and H. Bannerot.
1988. Selection methods in the common bean (Phaseolus vulgaris).
p. 503-542. In P. Gepts (ed.), Genetic Resources of Phaseolus beans.
Kluwer, Netherlands
• Silbernagel, M.J. 1986. Snap Bean Breeding. p. 243-282. In Bassett,
M. (ed.), Breeding Vegetable Crops. AVI Publ. Co., Westport, CT.
• ASERECA [Association for Strengthening Agricultural Research in
Eastern and Central Africa] . 2009 Proceedings of the Regional
Stakeholders’ Workshop on Snap Beans Commodity Value Chain by
Maureen Katafiire, Michael Ugen and Mwamburi Mcharo

23. THANK YOU