Left: Guadeloupe breeder, Kodjo Tomekpe, with a CIRAD hybrid.
Right: Jean-Pierre Horry inspects a commercial scale planting of CIRAD 01.
Innovative Breeding at CIRAD
Since the inception of modern day conventional banana breeding in the 1920s in Trinidad, the basic approach had been to cross wild species or fertile diploid cultivars (male parent) onto existing popular triploid cultivars (female parent) to produce hybrids which hopefully combined disease resistance with acceptable agronomic and organoleptic qualities. However, this had a number of drawbacks including inefficient production of hybrids, the poor agronomic, organoleptic and post harvest qualities of the end product tetraploids and most importantly it precluded recurrent selection.
In 1986 Harry Stover and Ivan Buddenhagen published a radical paper on banana breeding (see Fruits Vol 41 pp 175-191) where they suggested resynthesizing new triploids by first doubling the chromosome number of suitable diploids, using the chemical colchicine, followed by crossing with other diploids. Successful breeding is a numbers game. The beauty of this approach was it meant that highly fertile diploid parents could be utilized ensuring many progeny for assessment and the incorporation of disease resistance genes from several sources to promote the durability of the disease resistance.
This approach formed the basis of the CIRAD program which commenced breeding in the late 1980s. The main emphasis of the breeding program was to develop hybrids with Sigatoka leaf disease resistance to reduce the need for fungicide application. Within a few years several interesting disease resistant hybrids had been developed. CIRAD needed to know their reaction to subtropical race 4 Fusarium wilt so the hybrids were sent to Australia in the late 1990s.
Closeup of CIRAD 01 bunch (left). CIRAD 01 has performed well in European consumer taste assessments.
Banana Streak Virus Causes Hiatus
Some may remember that unusual symptoms were detected in the hybrids by Qld DPI in the field trials in southern Queensland in the late 90s which were confirmed to be due to Banana Streak Virus (BSV). Everybody was astonished as quarantine inspections and lab tests indicated the material received was disease free. What was eventually discovered, for the first time in science, was that the BSV strain present was actually integrated into the DNA of the hybrids and was activated by stresses including the tissue culturing process. Fortunately it was found that not all parents used in the breeding program were carriers of this latent form of BSV so CIRAD regrouped, confining its activities to the ‘clean’ parents.
Hybrid CIRAD 01 Commercial Potential Investigated
Subsequently a group of BSV free hybrids were developed with the best of these, CIRAD 01 (see figures 3 & 4), being advanced to 6 multilocational grower evaluations in Guadeloupe and nearby Martinique. Features of this hybrid are:
- Moderate sized bunches [about 30% lighter than Williams Cavendish] but is quicker cycling in ratoons. The quicker cycling makes up for most of the difference in bunch size. Smaller bunches are also a potential advantage from a workplace health and safety perspective.
- Resistant to yellow and black Sigatoka.
- Resistant to burrowing nematodes and lesion nematodes
- Intermediate in height [about a metre taller than Williams Cavendish]. Associated with this it is more susceptible to wind damage. To offset this more attention may be needed to crop management that lessens plant height (e.g. plant crops and nurse suckering) as well as ensuring bunch support is in place.
- Well appreciated by consumer panels in metropolitan France – the same as Cavendish in many respects.
- Slightly shorter fruit than Williams.
- Longer fruit shelf-life than Williams (6-8 days vs 4-5 days)
- Requires screening for Fusarium wilt in Australia. If it has any tolerance of tropical race 4 this would be a real plus.
Major emphasis is now being placed at several stages in the breeding program on the development of dwarf selections. This includes the tissue culture multiplication of several thousand plants of CIRAD 01 seeking somaclonal variants that are dwarf in stature as well as chemical mutagenesis to do the same.
What does the Future Hold?
"We don’t know all that the future holds but we can be certain it will involve changes of various kinds which will likely include incursions of exotic pests and diseases and further restrictions on chemicals and how they can be applied plus increased competition in the marketplace. Sourcing a range of germplasm that is resistant to pests and diseases for evaluation is an important component of being prepared. New varieties may also offer the opportunity for managing supply in the marketplace. Collaboration between Queensland DAFF and CIRAD should continue to be fostered for the synergies it brings to the R&D efforts and the associated benefits to the respective banana industries."
For more information:
Frederic Bakry
CIRAD
Email: frederic.bakry@cirad.fr