The choice of disease-resistant and -robust varieties forms the basis for integrated and organic fruit production, and is thus an important factor for resource-efficient, sustainable and resilient production in all production systems.
Aim of Work Package 3
The joint experimental activities of Agroscope, The Research Institute of Organic Agriculture FiBL and the involved cantonal agencies will in future bring together a large amount of information on resistance and robustness to the main plant diseases. This knowledge will serve to identify fruit varieties suitable for growing with reduced crop protection, and which thus provide significant added value compared to the standard varieties. The project phase will see the development of an experimental infrastructure and of the test method for identifying varieties that produce marketable fruit with reduced use of crop protection products.
Developing a testing network
For many years now, apple varieties have been tested both under conditions that are common in practice and with strategies involving reduced crop protection at Agroscope’s Wädenswil site and at FiBL’s site in Frick. Numerous new international varieties and crossings from Agroscope’s breeding programme have been tested.
For the remaining fruit species, variety testing has heretofore primarily taken place under ideal practical conditions, with agronomic suitability for cultivation and fruit quality being the key concerns. As part of RESO, the fruit species pear, cherry and pIum are now also being tested with a reduced-crop-protection method at Agroscope’s testing sites. For this, in Wädenswil the plots for the pear variety testing were divided into two blocks and in 2020 the first trees were planted. Their first fruits have now been harvested. Additional testing plots are being created at Breitenhof (Canton of Basel Land) for cherries and plums to test the suitability of varieties for cultivation with reduced crop protection.
To obtain meaningful results on the performance of a new variety using reduced crop protection, the variety must be tested at several sites and in fairly large blocks. Consequently, further plots were planned at Flawil (Canton of Sankt Gallen), Frümsen (Sankt Gallen) and Conthey (Valais) sites in partnership with the cantonal agencies and trees were ordered for the tests. These trees are currently being raised in nurseries before they can be planted on the new test plots in spring 2024.
Choice of varieties
A wide range of varieties from different maturity groups was selected in consultation with all the involved project partners. Here, we drew on the knowledge amassed by Agroscope and FiBL from their many years of variety testing, as well as on the experience of advisory services, the commercial sector and production.
For the apple varieties, mainly varieties with Rvi 6 scab resistance that were selected. Among these are several varieties that are already somewhat better known, such as Bonita, Ladina and SQ 159 (Natyra®/MagicStar®). In addition, several brand-new or as-yet relatively unknown varieties such as Delcored, WUR 037 (Freya®) and Ipador (Giga®) as well as several advanced breeding numbers were selected.
With pears, besides the already somewhat-better-known varieties such as CH 201 (Fred®) and Celina (QTee®), novelties and still-largely-unknown varieties such as PremP009 (PiQa® BOO®), Harovin Sundown and Bay 6474 (Alessia®) are being tested.
Resistance breeding for cherries and plums is less advanced than for apples. Here, hypersensitivity to sharka in plums is the only resistance in the proper sense. Robustness is probably observed, but given that most of the breeding programmes to date have worked under ideal cultural conditions, highly susceptible varieties are recognised whilst highly robust ones are not. For cherries and plums, variety selection was based on the criteria of relevance, potential, one’s own observations and genetic diversity.
For purposes of comparison, the respective standard varieties such as Gala or Conference are included in the tests for all fruit species.
Choice of crop protection strategy
Several issues must still be clarified when developing strategies for reduced crop protection. Site-specific characteristics such as climatic conditions and disease pressure on the plots must be borne in mind here. The reduced cop protection strategy will therefore not look the same at each site, but will be determined by a group of specialists from among the project partners for each site. Here it will also be possible to draw on many years of experience from trials like Agroscope’s ‘low-input trial’. The reduced-use strategies in the experimental plots must be selected so as to allow variety-specific differences to be identified: in other words, so that, in the ideal case, the most-susceptible variety exhibits a no-longer tolerable infestation, while the most robust variety produces impeccably.
In the practical experimental work, however, it often proves difficult to maintain a suitable disease pressure – although testing at several sites increases the likelihood of substantiated statements about the resistance or robustness of a variety being made in future.
Crop protection strategy trial at the UFL in Morges
In 2022 a crop protection strategy trial was conducted in an apple orchard in Morges (Canton of Vaud) in conjunction with the project partner Union Fruitière Lémanique (‘Lake Geneva Fruit Union’, UFL). The trial is meant to yield findings for future crop protection trials within the RESO project. In the trial, an intensive and an extensive organic crop protection strategy were tested on the apple varieties Daliclass, Rustica and Ladina. The scab-resistant varieties Rustica and Ladina are among the RESO varieties and are also planted in the new RESO plots. In the trial, targeted scab control is carried out in both strategies according to the RIMpro forecast model, whereby in the extensive strategy, crops are only treated when the risk is high. Myco-Sin and sulphur are applied for the preventive control of scab, switching in summer to a strategy using Armicarb and sulphur. Prior to the harvest both strategies carry out final treatments with Myco-Sin, with Blossom Protect also being used in the intensive strategy.
Initial field surveys show that the incidence of disease could be kept very low both in the intensive and extensive strategy. The occurrence of scab symptoms was largely prevented. There was only a very slight scab infestation on the fruits on Daliclass in the extensive strategy.
Some of the crop were put into storage to investigate the occurrence of storage diseases afterwards.
Initial findings from the ongoing trials
Agroscope’s pome-fruit variety testing is currently pursuing a strategy in which standard Integrated crop protection is applied up to post-flowering, followed by a reduced strategy with Vitisan and Myco-Sin. Over the past two years, significant pressure from powdery mildew has become entrenched in apples and major variety-specific differences are evident each year. However, particularly in the case of powdery mildew, these differences are not very dependent on the crop protection strategy. By contrast, differences between varieties for Marssonina leaf blotch, rain spots and storage diseases were increasingly noted with the reduced crop protection strategy. So far, no resistance breakthroughs for the largely Rvi 6 scab-resistant varieties have been observed. With the pears, no differences between the strategies have been observed to date in the newly planted pear orchard.
Pome-fruit variety testing has been established at FiBL for many years now.
New national and international breeding numbers and varieties are tested for a test phase of at least 4 years under organic growing conditions using two different methods: (1) practical (with thinning as well as standard crop protection; (2) very-low-input (without thinning and with reduced crop protection). The agronomic potential can be seen under the practical conditions, whilst the genetic potential of the varieties can be seen under the low-input conditions. Differences between the two methods can be detected for different varieties, particularly in terms of scab and Marssonina infestation. Resistance breakthroughs in Rvi 6 scab-resistant varieties have already been observed.
