The horticultural sectors rely in the production of many crop plants on the use of peat substrates. Due to ecological reasons, the use of peat has to be reduced or if possible eliminated in the horticultural production systems and alternative, peat-free substrates are needed.
The aim of this project is to study the use of peat-free and peat-reduced substrates in the horticultural production system with an holistic approach to support producers with scientifically based knowledge and to offer applied solutions for a sustainable horticultural production.
The goal of this joint project is the improvement of existing, as well as establishment of novel defence mechanisms against diverse pests. Meloidogyne chitwoodi, a quarantine-status endoparasitic root knot nematode is one of the major pests of potatoes. PVY (potato virus Y) and PLRV (potato leaf roll virus) are the regulated non-quarantine viruses, which are transmitted by the aphids, e.g. Myzus persicae. The tendency for the reduction of pesticide use will result in a significant increase in the occurrence of PLRV, as aphids that have taken up PLRV-virions stay viruliferous for their entire life. In the potato germplasm there is a single gene originating from S. stoloniferum, which results in PVY immunity, which is, however, linked with male sterility. Therefore, new and complementary resistance sources need to be identified for both viruses.
Additionally, the project aims at development of novel levels of pathogen resistance. The efficient replication of PVY depends on successful hijacking of host translation mechanisms. Therefore, the inactivation of the translation initiation factor (eIF4e) results in the inhibition of viral replication. The efficiency of this approach against infection by PLRV and TRV will be tested as well.
Following the damage to sieve elements in plants, sieve plates can be closed either temporarily by phloem proteins (P-proteins), or permanently by callose deposition. Inactivation of genes responsible for P-protein synthesis will result in permanent closure of sieve plates[h1] [SH2] . This may prevent flow of nutrients towards the feeding site induced by M. chitwoodi, resulting in parasite starvation and leading to increased resistance.
The tobacco rattle virus (TRV) is transmitted by ectoparasitic nematodes belonging to the genera Trichodorus and Paratrichodorus. As currently available nematicides show only limited control against these viral vectors, the efficient resistances originating from wild potato species need to be identified.
Additionally, the project aims at development of novel levels of pathogen resistance. The efficient replication of PVY depends on successful hijacking of host translation mechanisms. Therefore, the inactivation of the translation initiation factor (eIF4e) results in the inhibition of viral replication. The efficiency of this approach against infection by PLRV and TRV will be tested as well. Following the damage to sieve elements in plants, sieve plates can be closed either temporarily by phloem proteins (P-proteins), or permanently by callose deposition. Inactivation of genes responsible for P-protein synthesis will result in permanent closure of sieve plates. This may prevent flow of nutrients towards the feeding site induced by M. chitwoodi, resulting in parasite starvation and leading to increased resistance.
Additionally, the project aims at development of novel levels of pathogen resistance. The efficient replication of PVY depends on successful hijacking of host translation mechanisms. Therefore, the inactivation of the translation initiation factor (eIF4e) results in the inhibition of viral replication. The efficiency of this approach against infection by PLRV and TRV will be tested as well.
The northern root-knot nematode Meloidogyne hapla leads to relevant economic losses in carrot production in temperate zone by yield reduction and considerable quality losses of infested batches. Application of chemical nematicides is forbidden in Germany. Carrot cultivars resistant to M. hapla are not available so far. Breeding approaches are limited becouse of the lack of resistance resources and genetic knowledge.
In a former JKI project was proven that in a number of Daucus wild relatives such as D. c. ssp. azoricus, D. c. ssp. commutatus, D. halophilus and D. capillifolius resistances to M. hapla are available. These resistances were proven also after subsequent backcrosses to the cultivated carrot D. c. ssp. sativus Hoffm. (Arc.). Aim of the project is to lay foundations for pyramidisation of two or more resistance genes against M. hapla and to provide basic material for practical breeding.
The horticultural sectors need professional solutions to master the urgently needed ecological switch to peat-free or peat-reduced growing substrates. The ToPGa project thus focuses on investigating and evaluating the effects of the use of peat-reduced substrates. Only with the help of such a comprehensive examination can recommendations be given to the practice for switching to peat-reduced substrates. In the project, researchers from various fields are working together with the aim of working on the various problem areas of the use of peat-reduced substrates and developing interdisciplinary approaches to reducing the use of peat for all horticultural sectors.
Both the optimisation of crop security in the use of substrate raw materials such as wood fibre, coconut, substrate compost etc. and the investigation of new substances that have so far been used little or not yet in horticultural growing media are therefore urgently needed. Currently, peat substitutes used on a large scale, such as coniferous wood fibres, may decline in the future due to forest restructuring; coconut is criticised for socio-ecological reasons. New substances, which are available in large quantities, are needed in order to provide the quantities of high-quality peat substitutes required in the future. For socio-ecological reasons, renewable peat substitutes from regional cultivation are to be preferred. Therefore, as an alternative to coconut fibre, the fibre nettle would be interesting as a peat substitute. The fibre nettle is a variety of the large stinging nettle (Urtica dioica L.), whose fibre content has been increased by breeding.
Within the framework of the project, the JKI Institute of Crop and Soil Science (1) is investigating the sustainable cultivation and yields of three newly bred fibre nettle clones within an already established agroforestry system and in the "open field". In contrast to other renewable raw materials (e.g. typha) which can be used as peat substitutes, the cultivation of nettle fibres can take place on large areas and delivers a high fibre yield per unit area. The resilient cultivation in the agroforestry system favours the nettle (wind protection, shading); an additional incentive for farmers is provided by the wood production and the subsidy of tree strips. (2) Nettles are nitrogen-intensive plants. The C:N ratio of the plants is to be optimised via various N fertiliser levels in order to reduce the risk of N immobilisation in the growing medium. Wood fibres from the tree strips (poplars) of the agroforestry system are to be combined with the fibres of the nettle according to the desired characteristics of the substrate. (3) An estimation of the potential of nettle cultivation will be carried out with regard to site conditions and site requirements.