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  • Author or Editor: A. Vágújfalvi x
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Testing cereal frost tolerance goes back for decades in the Agricultural Research Institute, Martonvásár, Hungary. The climatic programmes used in the plant growth chamber have proved to be fairly efficient, but these methods are time-consuming and have become quite expensive in recent years. An attempt was made to shorten this process by reducing the cold hardening phase, and the freezing test has been simplified and shortened by measuring the relative conductance of leaf segments frozen in a liquid freezer. Frost-tolerant and sensitive wheat lines were tested, and the sensitivity of the system was checked by testing single chromosome substitution lines. Differences were found for all lines frozen at different temperatures. To reduce the costs of the experiment it was attempted to cold-harden the plants not only in a growth chamber but also in a cold room under very low light intensity and it was found that even under thess unfavourable conditions the plants developed a certain level of frost tolerance. The simplified frost tolerance test has proved to be effective, but requires further improvement due to the unsatisfactory significance levels.

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The mobilization of carbohydrates, especially sucrose, is considered very important during both the cold acclimation process and water stress, while sugars also promote floral transition and cold hardiness. Chinese Spring (CS) 5AL and 5DL deletion lines were studied for the physical assignment of the gene(s) regulating stress-induced sugar accumulation. To separate the effect of cold from that of water deprivation, the seedlings were raised in hydroponics, and apart from the cold, the effect of PEG-induced water stress was also evaluated in a time course experiment. The genes affecting stress-induced carbohydrate accumulation were assigned to the same chromosomal bins, which contain the vernalization genes Vrn-A1and Vrn-D1, on the long arms of chromosomes 5A and 5D, respectively. Sugar accumulation was found to be controlled by Vrngenes in an epistatic manner at least at the beginning of the cold treatment. In the case of cold treatment, Vrn-A1proved to be more effective than Vrn-D1, while in the case of osmotic stress the gene assigned to the long arm of chromosome 5D seemed to be more effective at regulating sugar accumulation than its counterpart on 5A.

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Freezing tolerance is a quantitative trait, determined by many genes and also influenced by environmental factors. Thus, the development of reliable testing methods is a prerequisite both for the identification of quantitative trait loci (QTLs) and for the identification of the genes behind the QTLs. Transformation methods proved to be effective in the direct verification of isolated genes involved in low temperature stress responses. In order to develop freezing tolerance, winter cereals must be adapted through a cold hardening period, which not only influences cold adaptation but also initiates the vernalization process necessary for flowering. Recent and ongoing studies are endeavouring to uncover the relationship between freezing tolerance and vernalization response at the genetic and molecular levels. This review aims to explain cereal freezing tolerance on the basis of recent discoveries in the areas outlined above.

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Acta Agronomica Hungarica
Authors: L. Sági, M. Rakszegi, T. Spitkó, K. Mészáros, B. Németh-Kisgyörgy, A. Soltész, F. Szira, H. Ambrus, A. Mészáros, G. Galiba, A. Vágújfalvi, B. Barnabás, and L. Marton

Research with transgenic plants in the Agricultural Research Institute of the Hungarian Academy of Sciences is primarily related to applications that are essential for the genetic improvement of cereals. The two main directions are connected to wheat and maize breeding and are focused on improving agronomic and nutritional traits. This paper highlights experiments in these areas, which are conducted in national as well as international collaborations. The transparency of this work is ensured by the dissemination of information about approved confined field tests to the public via the internet.

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