# Use of apple genetic resources in apple breeding programmes at Inra: present status and perspectives

François Laurens

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François Laurens. Use of apple genetic resources in apple breeding programmes at Inra: present status and perspectives. European Malus Germplasm, European cooperative programme for crop genetic resources networks., Jun 1995, London, United Kingdom. hal-01603372

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EUROPEAN COOPERATIVE PROGRAMME FOR CROP GENETIC RESOURCES NETWORKS (ECP/GR)

# European *Malus* Germplasm

Proceedings of a workshop

21-24 June 1995

Wye College, University of London

Helen J. Case, editor
# Use of apple genetic resources in apple breeding programmes at INRA: present status and perspectives

F. Laurens

Station d'Amélioration des Espèces Fruitières et Ornementales, Centre INRA Angers,
49071 Beaucouze CEDEX, France

French apple breeding programmes are carried out at INRA Angers and INRA Bordeaux, and coordinated by INRA Angers.

## Breeding aims

Aims of the dessert apple breeding programmes are concentrated on three main points:

1. The primary breeding objective is to release high-quality fruits. Attractiveness, taste, long storage life and shelf life are then taken into account.

2. Disease and pest resistance. All the material released is scab resistant. We try also to include in the selections resistance or less susceptibility to mildew (Podosphaera leucotricha), rosy apple aphid (Dysaphis plantaginea) and fire blight (Erwinia amylovora).

3. Tree habit. J.M. Lespinasse at INRA Bordeaux is performing very interesting work on this topic. There is a large variability for tree habit in apple; from Wijcick to Granny Smith, a wide range of habit exists (Lespinasse 1977).

While almost all the apple breeders in the world highlight their programmes on spur-type trees, INRA's breeding aim is to create weeping and not too vigorous trees, which give good and regular cropping, and are easy to prune and harvest. Parents which transmit the character for one fruit per cluster are also introduced in the scab-resistant genotypes.

## Breeding population set

A major part of the breeding population (70%) consists of genotypes coming from the previous selection cycle. All are scab resistant. Commercial varieties and other new susceptible (to scab) accessions are also included in the population (about 20%). Old and local varieties are also present, but in a very small amount (2%).

The breeding population is composed of 30 genotypes, and 30 crosses are made between them each year.

Selection inside the main population is performed according to two common objectives: fruit quality and scab resistance. It is structured in three subpopulations which have more specific objectives.

**Subpopulation no. 1: management of scab resistance.** The Vf gene from *Malus floribunda* clone 821 has been used in all the breeding programmes throughout the world. Vf resistance was considered durable until 1984, when the first scab symptoms on Vf selections were detected in the field at Ahrensburg (Germany) which proved the existence of a new race of *Venturia inaequalis*. Studies on this new race have been performed at the Pathology Station of INRA Angers (Parisi *et al.* 1993). For several years, strategies have been carried out at INRA Angers, to select efficient and durable resistance (Laurens and Lespinasse 1995). Seventy percent of the crosses realized each year aim to manage scab resistance. Table 1 shows the sources of scab resistance in use. Vf is still the most used. Other major genes of resistance (Vr, Vjonsib) have been included. Most of the polygenic sources of resistance are selections of Antonovka. Other
included. Most of the polygenic sources of resistance are selections of Antonovka. Other interesting sources of durable resistance have been found in old and local French cultivars. These are starting to be included in the breeding programmes.

<table><caption>Table 1. Parents used for scab resistance management programmes at INRA Angers</caption><thead><tr><th>Resistance</th><th>Varieties/cultivars</th></tr></thead><tbody><tr><td>Vf</td><td>R. Beauty x Mf.821 → F2 26829-2-2 → 6-7 generations</td></tr><tr><td>v</td><td>commercial varieties (Golden, Gala)<br>new released varieties<br>old French varieties (Rtte Clochard, Rtte du Man)</td></tr><tr><td>V</td><td>Vr → Nova easygro<br>V jonsib<br>generos</td></tr><tr><td>Polygenic</td><td>Rouchetaude<br>Antonovka<br>old varieties</td></tr></tbody></table>

Subpopulation no. 2: add in one genotype; resistances to various pests and diseases. Some selections which are carrying resistances to scab, mildew, rosy apple aphid and fire blight have already been selected. Mildew-resistant parents used are White Angel and essentially *Malus zumi* derivatives (PI2 gene). Various cultivars carrying multiple resistance (Prima, Florina) have also been used as parents (Table 2). Further crosses will be made to improve fruit quality.

<table><caption>Table 2. Various sources of resistance used in the breeding programmes of INRA Angers</caption><thead><tr><th>Resistance</th><th>Parents</th></tr></thead><tbody><tr><td>Mildew</td><td><i>M. zumi</i> (PI2)<br>White Angel<br>Robusta 5<br>Old French varieties</td></tr><tr><td>Multiple</td><td>Prima (Scab + Mildew)<br>Liberty (Scab + Fire blight)<br>Florina (Scab + Fire blight + Rosy Apple Aphid)<br>Priscilla (Scab + Fire blight + Rosy Apple Aphid)</td></tr></tbody></table>

Subpopulation no. 3: add scab resistance and good tree habit characters which allow regular cropping and facilitate picking procedures. Various parents have been used (Granny Smith, Idared, Rome Beauty, Cassou); many selections came from the cross Idared × Prima.

### Cycle of selection

The cycle of selection is shown in Figure 1. The first part of the selection takes place in the greenhouse. All the seedlings are tested for scab resistance. After two inoculations, the susceptible plants are eliminated. The 5000 remaining resistant plants are planted in the nursery and tested according to their behaviour to mildew. After 18 months, the
most mildew-resistant trees are planted in the orchard. Then, 3-4 years of cropping are useful to test fruit quality (appearance, taste, storage abilities), assess tree habit and to detect the behaviour of each individual against diseases and pests present in the orchard. An index of selection is used which takes all these criteria into account. The best 35 individuals are then selected.

<figure><img src="image_2.png" /><figcaption>Fig. 1. Apple breeding programme of INRA Angers: cycle of selection</figcaption></figure>

The next step of selection is at the national level (stage A varietal trials under the responsibility of INRA Angers, Fig. 2). Cultivars, selections (mutants or hybrids) from different countries and INRA's selections are tested together at three sites in France (INRA Angers; Ctifl Lanxade, southwest; Ctifl Balandran, southeast). Each year more than 100 accessions are introduced, grafted onto M9 and tested for 3 years. More than 40 criteria are used to characterize and evaluate them.

At the end of the experimentation, the best clones are selected to follow the next steps of selection (stage B trials); very few are released as commercial varieties.

A proportion of the tested material could be used as parents in further breeding programmes. The stage A experimentation is also a way to enlarge the apple collection.
Cultivars which proved to be interesting for at least one character are planted in the germplasm orchard.

<figure><img src="image_3.png" /><figcaption>Fig. 2. Stage A varietal test</figcaption></figure>

## Results

A few cultivars have been released from the dessert apple breeding programmes of INRA Angers. Some of them are issued from old cultivars which gave good fruit taste quality, resistance, etc.

Chantecler comes from a cross between Golden Delicious and Reinette Clochard, a local French variety which transmitted a very good taste. It is not scab resistant (LeLezec 1990).

Florina, a scab-resistant variety, is also resistant to rosy apple aphid and has a good behaviour against fire blight and red mites (Lespinasse et al. 1985).

Baujade was released in 1991. It is a green-skinned apple very similar to Granny Smith but scab resistant. Baujade has in its pedigree Reinette du Mans, an old French variety which gives Baujade more flavour than Granny Smith (Lespinasse et al. 1992).

A large number of promising scab-resistant selections have been selected. Four of them are being tested in large-scale trials at 12 sites in France (more than 50 trees/hybrid/site). In the next 2 years, one or two of them should be released.

## Perspectives

In the future, it is the intention of INRA to carry on with the creation of new cultivars. The released cultivars and advanced selections already exhibit a few interesting characters (at least scab resistance). But, in the long term, it is intended to associate more
characters in one individual: durable resistances, good fruit quality, good storage ability, no biennial bearing, trees easy to train.

A brief analysis of apple breeding and selection strategies developed around the world shows the similar characteristics: small size of population with a very narrow genetic variability, phenotypic selection, very high intensity of selection. This type of strategy is well-adapted for cultivar but entails in the long term an increase in the level of inbreeding and depletion of the genetic variability in the populations. The selection to enlarge the size of New Zealand's limited breeding population put emphasis on the diversity of genes contributed by each genotype rather than on its commercial value. So wild species, primitive cultivars, and cider apples have been included in a large breeding population (500 parents) that has been managed in order to maximize genetic variability.

Such a project could be set up in Europe. As described in Session 1 of this workshop, European countries have collected a large number of accessions. On the same basis as the New Zealand project, but on a larger scale, it could be possible to agree on a dynamic management strategy for European genetic resources. The aim of this project would be to manage the genetic variability present in European collections so that germplasm becomes more accessible to the breeders and is used more efficiently by them. But first, several steps are necessary:

1. Design a European germplasm network.

2. Characterize and evaluate all the accessions in order to get an estimate of the current genetic diversity. A lot of information can be obtained by studying the breeding strategies of other crops.

3. Forest breeders have been thinking for a long time about the management of the genetic variability in their breeding populations. Noiton started in 1992, in New Zealand, an ambitious apple breeding programme based on forest knowledge (Noiton and Shelbourne 1992). Some details of this programme were provided by Dr Kellerhals, however, it is worth restating some facts of this programme. The primary aim was to—

4. Facilitate exchanges of material.

This new method of managing apple genetic resources will require a long-term commitment, but it must be done.

## References

Laurens, F. and Y. Lespinasse. 1995. Stratégies génétiques pour créer des variétés de pommier (Malus x domestica) résistant durablement à la tavelure (Venturia inaequalis). in Xième colloque sur les Recherches Fruitières INRA-Ctifl. Angers 15-16 mars 1994 (in press).

LeLezec, M. 1990. Fiche variétale de Belchard® Chantecler. L'Arboriculture Fruitière, 430.

Lespinasse, J.M. 1977. La conduite du pommier, types de fructification; incidence sur la conduite de l'arbre. Eds Invuflec-INRA. 80p.

Lespinasse, Y., J.M. Lespinasse et M. LeLezec. 1992. Baujade. Une nouvelle variété de pommier résistante à la tavelure. L'arboriculture Fruitière 454:15-16.

Lespinasse, Y., J.M. Olivier, J.M. Lespinasse et M. LeLezec. 1985. "Florina-Querina": la résistance du pommier à la tavelure. L'arboriculture Fruitière 378:43-47.

Noiton, D. and C.J.A. Shelbourne. 1992. Quantitative genetics in an apple breeding strategy. Euphytica 60:213-219.

Parisi, L., Y. Lespinasse, J. Guillaumes and J. Krüger. 1993. A new race of *Venturia inaequalis* virulent to apples with resistance due to the Vf gene. Phytopathology 83:533-537.