The tomato Fusarium resistance gene I-2 confers resistance to F. oxy-sporum f. sp. lycopersici race 2, which expresses the corresponding aviru-lence gene avrI-2. To elucidate the molecular basis of this gene-for-gene interaction, we initiated a search for the avrI-2 gene. Gamma irradiation mutagenesis, using (137)Cs, was performed to generate an avrI-2 mutant of F. oxysporum f. sp. lycopersici. To this end, a race 2 isolate was first transformed with a phleomycine resistance gene and a GUS marker gene in order to distinguish mutants from contaminating isolates. A total of 21,712 mutagenized colonies was tested for loss of avirulence on I-2-containing tomato seedlings. One mutant was selected that showed the expected loss of avirulence but, surprisingly, also showed reduced pathogenicity toward susceptible tomato plants. DNA analysis was subsequently used to visualize genomic changes in the mutant. Southern analysis on contour-clamped homogeneous electrophoretic field blots demonstrated a translocation of a 3.75-Mb chromosome in the mutant. Random amplified polymorphic DNA and amplified fragment length polymorphism analysis identified at least nine polymorphisms between the wild-type and mutant isolates. Most of these polymorphisms appeared as extra fragments in the mutant and contained repetitive DNA sequences.
The EU project CLOSYS aimed at developing a CLOsed SYStem for water and nutrients in horticulture. The main objective was to control water and nutrients accurately such that pollution is minimized and crop quality enhanced. The closed system as developed in this project consists of crop growth models and substrate models, a new substrate, an expert system, a real time controller, fluorescence sensors, ion-selective sensors and a technical infrastructure.Plant model: Mechanistic models for rose and sweet pepper were build and self-learning capacity was introduced. The models simulate crop growth, and demand and uptake of water and individual nutrients.Plant sensor: A fluorescence imaging system was developed and tested to be used as an indicator for plant performance and stress factors.Nutrient sensor: An on-line multi-ion sensor measures the concentration of individual nutrients pH and EC of the recirculating water in the greenhouse.Substrate model: A 3D substrate model simulates the water and nutrient flows in the substrate depending on the root absorption and fertigation.Substrate: A rockwool substrate with improved physical and chemical properties was developed to allow a better control of water and nutrient fluxes in the root-zone.Expert system: The expert system, using model and sensor information and weather forecasts, determines a daily plan for fertigation. This plan contains the setpoints for the real time controller.Real time controller: The real time controller controls the water and nutrient supply. It upgrades the fertigation parameters (irrigation EC, dose and frequency) to satisfy the set-points issued by the expert system, depending on current status of the system and on time constants and dynamic characteristics of the system. Technical infrastructure: All subsystems were integrated such that they can request data from the irrigation computer database. With these data, new set points for fertigation are calculated, whereafter the irrigation computer executes the requested tasks.Closed system: All components together form the closed system for water and nutrients. The performance of the closed system was compared to a standard sweet pepper growing system. The system has been running satisfactorily during a prolonged period (1 and a half year). Water and nutrient use, its availability in the rooting zone as well as the recirculating drainage water were controlled accurately. INTRODUCTIONIn greenhouse horticulture nutrients are usually supplied together with water. To prevent any shortage growers use excess amounts of nutrients and water. Even in the case a recirculation system is used, growers regularly drain nutrients and water to the environment to prevent imbalances of the nutrient solution in the root zone. As in present production systems nutrients and water are always supplied in excess amounts, possibilities to control and to plan crop growth and product quality by a regulated water and nutrient supply are hardly used by growers. In greenhouses, compared to open field production, a...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.