A multidisciplinary approach for damping-off resistance in spinach

Spinach is an important component of baby-leaf salads both in organic and conventional production systems. As the organic spinach production is increasing in its importance, demanding use of seeds without chemical seed treatments (fungicides), the problem of ‘pre and post emergence damping-off’ has become more apparent. Also for conventional baby-leaf production the use of fungicides is under pressure with respect to food safety, since for the fresh market baby-leaf is harvested already three weeks after sowing and occasionally seed tissue with coating material is being included in the harvest. This implies a growing market for organically or non-chemical treated seeds for both organic and conventional farming systems.

Non-chemically treated spinach seeds can suffer seriously from damping-off and root rot diseases. In the USA, the largest market for baby-leaf spinach seeds, 90% of the damping-off is caused by Pythium (S. Koike, pers. comm.). Also in Europe and the Netherlands, Pythium species seem important pathogens (M. van Diemen, pers. comm.), but this needs more study. Variation in response to damping-off has been observed between cultivars, but also between seed lots of the same cultivar, and even within a seed lot. Apart from problems with pathogens, breeders also experience that seed vigour plays a role. 

In this project proposal components of resistance/tolerance and seed vigour will be studied simultaneously to answer the following research questions:

  1. Are we able to demonstrate that there is a genetic
    base for variation between cultivars in resistance/tolerance to
    damping-off, based on either resistance/tolerance to Pythium
    spp. or components of seed vigour, as in order to breed for
    resistance/tolerance to damping-off the existence of genetic variation
    for this trait or traits is essential.
  2. Are we able to develop reliable screening tests to screen for resistance/tolerance to Pythium spp. using seed lots with uniform levels of vigour?
  3. Are
    we able to develop reliable screening tests for vigour and use these
    and the tests developed under point 2 to demonstrate the effect of seed
    vigour in relation to damping-off?
  4. Can we unravel the genetics behind components involved in resistance/tolerance to damping-off?
  5. What are the mechanisms involved in resistance/tolerance to damping-off?

The major aim of the project is to develop a breeding strategy for spinach to cope with damping-off. We propose to achieve this by following a multidisciplinary approach using the combined knowledge and expertise of seed technologists, plant breeders and soil-phytopathologists.