Publicaties

Health Management for Seeds and Other Organic Propagation Material

Koch, E.; Groot, S.P.C.

Samenvatting

Propagation material is an integral part of the crop produc­ tion chain. The genetic constitution of the cultivar should guar­ atee optimal adaptation to the growing conditions and a good yield with the desired quality characteristics. Healthy and vig­ orous seeds, seed tubers, or transplants are essential for rapid establishment of the crop. Use of poorly germinating seeds or seed bers infected with pathogens results at least in losses bu t often Ill crop failure. The term "propagation material" refers to seeds and· veg­etatitve material such as seed tubers (e.g., potato), bulbs (e.g., onions, shallots, and some ornamentals), cuttings (trees and shrubs), young plants (transplants) produced from either cut­tings or seeds, and grafted plants (as is common for fruit trees and becoming increasingly important for vegetables such as tomatoes, peppers and cucurbits) Although the genetic material used in organic farming i s often the same as that used in con­ ventional production, cultivars with trait5 that are less impor­ tant or even unwanted in conventional farming are sometimes preferred in organic farming. This holds true, for example, for cultivars that are adapted to the local soils and are resistant to pests and diseases common to the area or for those that exhibit structural features that contribute to disease control or weed suppression . Examples of the latter are tall wheat cultivars that provide greater ground cover or have a higher light interception level or leaf area index than shorter and less competitive culti­ vars (Drews et al., 2009). The use of chemical crop protectants and fertilizers in the production of conventional propagation material has enabled improvement in the quality of seeds and seed tubers, especially in the high-value seed market. Obtain­ ing similar high-quality propagation material under organic production conditions presen ts a challenge, especially with crops for which the seeds are not the product that is normally harvested. The term "vigor" is defined as the potential of seeds to germinate and produce good-quality seedlings, even under suboptimal field conditions. Making nutrients available from organic fertilizers requires microbial activity. With cold soils in the spring, microbial activity is low. In order to mobilize enough nutrients, the use of highly vigorous seeds that ger­ minate rapidly and produce seedlings with fast-growing root systems is important in establishing a new organic crop. Fewer options for disease control are available in organic farming, so avoidance of seedborne diseases is more important than in con­ ventional crop production .