Description: Loss of meristematic activity in the embryonic or plantlet stage can occur with several vegetable crops, including tomato, pepper, broccoli and kohlrabi. This phenomenon can cause a severe loss of production and reduction of quality of the plantlets. This loss of meristematic activity has both a genetic and an environmental origin.
Research objectives: The project aims to understand the genetic and physiological factors that influence the response of the shoot apical meristem (SAM) to environmental conditions. This acquired knowledge will support seed companies to breed for varieties that are adapted to growth under low energy input conditions, including varieties that are less susceptible to shoot apical meristem determination (blindness, budless or shoot-less). The project will also enable seed companies to improve their seed treatment protocols for varieties susceptible for blindness and will provide nurseries with information regarding critical environmental factors which induce shoot apical meristem determination during transplant production. Brassica and tomato are chosen as model species because they allow a combination of physiological and genetic approaches and the fact that with both crop species considerable economic losses occur as the result of the appearance of blind plants. Most Dutch seed companies and plant raisers are actively involved in the project.
Results and products: The project will start with an inventory of the experience from the participating partners with regard to the occurrence of blindness. The information will related to available scientific information on meristem maintenance and differentiation and compiled in a report. The report will be discussed in an internal workshop of the consortium. Experiments will be performed with a selection of sensitive and tolerant brassica and tomato lines to analyse in more detail the response of the plantlets to light conditions in interaction with other environmental factors. This will result in diverse protocols that can induce blindness in varying degrees with susceptible material. These protocols will be used for the physiological analyses. The protocols inducing severe degrees of blindness will be used for phenotyping in segregating populations and by the seed companies in breeding for non-susceptible varieties. The more detailed identification of key environmental factors will provide the nurseries with critical information to prevent the development of blind plants during plant raising. The identification of key environmental factors and their interaction with genotypes, can be used in the breeding for adapted plant varieties. A genetic analysis will be done, aiming to identify quantitative trait loci (QTL) for blindness sensitivity in both crops. The expanding sequence information of the Brassica rapa and tomato genomes and the large collection of publicly available ESTs provide tools for marker development, and the identification of candidate genes underlying the blindness QTL(s). A more detailed phenotyping of the induced blind plantlets will be performed, both at the morphological and at the molecular level (gene expression). The morphological analyses will comprise studies to pinpoint the moment during meristem development when meristematic activity is lost. The results of the experiments will be integrated into a description of meristem development in relation to environmental factors with the focus on the switch to determinate growth. Besides several scientific publications, this will result in recommendations to the seed companies and plant raisers. |