Plant breeding for organic and sustainable, low-input agriculture

Organic outdoor tomatoes - regional screening and breeding in Germany
Bernd Horneburg, Heiko C. Becker
Department of Crop Sciences, University of Göttingen, Göttingen, Germany
Tomatoes are the most important vegetable in Germany, but more than 90% of the consumption
are imported. One of the major obstacles for increased production is the breakdown of outdoor
tomato production. Increasing infections with late blight (Phytophthora infestans) have almost
eliminated commercial cropping and seriously impaired private production. The aim of the
project during the years 2003-2006 was 1) to screen for and recommend suitable open pollinated
varieties for organic outdoor production and 2) develop a regional breeding program within
organic agriculture.
The screening was based on 3500 accessions. In close contact with genebanks, NGOs, seed
trade, and private seed savers 92 varieties were selected for comparative trials at 3 locations in
central and northwestern Germany. The number of varieties was reduced from 2003 to 2006.
Some additional varieties with superior performance in a screening at one location were
included. Per location 2 replications with 2 plants (2006: 3 x 2) were grown. Layout and
maintenance of the plots favoured Phytophthora-infections.
Each year a group of 10-12 varieties was tested at 25 to 35 locations. Included were backyard
and market gardens, botanical and other public gardens, and research institutions.
Suitable varieties identified in the screening were used to make crosses to combine the important
traits earlyness, field resistance against late blight, high yield, and good fruit quality. The most
advanced crosses were included in the screening 2005-2006.
After 2 years of screening the share of commercial varieties was 9.1% and 31.8% were obtained
from genebanks. 59.1% of the most interesting varieties originated from NGOs and individual
seed savers. 4 years of screening and regional tests resulted in the top ten varieties with a high
field resistence against Phytophthora and favourable agronomic, morphological, and
phenological attributes. Included are wild-, cocktail-, salad-, processing-, and beefsteaktomatoes.
Seeds are available.
The high heritability of Phytophthora-infections on leaves and fruits, and for yield (>79%)
confirmed the suitability of the experimental design. For all traits the varieties were the most
important variance component. Site specific adaptation, i.e. variety x location interaction, was of
minor importance or absent. For fruit infections variety x year interactions were stronger than
variety x location interactions.
As an example for the regional breeding program a wide cross between the wild tomato Golden
Currant and the salad tomato Matina is shown. Field resistance against late blight and long
harvest period of the wild tomato were successfully incorporated in the F5- and F6-generations
and resulted in the highest yield in the screening 2006.
The methodology for a regional breeding program is developed and needs to be put into practice!
We would appreciate co-operation with neighbouring countries with similar problems.
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