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Abstract: The rice Osmyb4 gene, coding for a MYB transcription factor, is expressed at low levels in rice coleoptiles under normal conditions and strongly induced at 4°C. Its overexpression in Arabidopsis thaliana plants increases biotic and abiotic stress tolerance and results in the accumulation of several metabolites, essential in defence response. The heterologous expression of the Myb4 transcription factor represents a promising potential approach to improve stress tolerance in crops, avoiding endogenous mechanisms that often co-suppress the transgene of interest. In order to explore the potential of the Osmyb4 gene to enhance tolerance toward multiple stresses in different host plant genomes, we generated transgenic tomato (Solanum lycopersicum L. cv. Tondino) plants. Like Arabidopsis, tomato plants overexpressing Osmyb4 acquired a higher tolerance to drought stress and to virus disease. However, the transgenic plants did not appear to be more cold tolerant than the WT, in any tested condition. The data obtained indicate that the specificity and the degree of Osmyb4 activity depend on the host genomic background. [Copyright &y& Elsevier]

Abstract: Accessions of Solanum torvum SW, a wild relative of eggplant, were collected in Java Island, Indonesia, and assessed for morphology, fertility, levels of resistance against both Ralstonia solanacearum and Fusarium oxysporum f. sp. melongenae, as well as the genetic diversity by using RAPD and I-SSR markers. When grown to maturity in the field in Bogor, Indonesia, plants were very vigorous and showed a high polymorphism in all characters examined among the accessions, except for the stem diameter and the number of branches. The relatively high heterogeneity in morphology and fertility could not be related to the geographical origin of the accessions surveyed, and was not corroborated by genetic analysis. By using RAPD markers, 8.4% polymorphism were detected in two genotypes (BML and BG1) among the 11 accessions analysed, whereas screening with I-SSR markers has resulted in 3.3% polymorphism in three accessions, BG1, CN1 and CN2. This therefore gives a global 4.7% polymorphism, individualising only four accessions among the 11 tested. Twenty nine accessions of S. torvum and eggplant, cv Pusa Purple Long used as positive control, were evaluated for resistance to R. solanacearum (race 1 biovar 3, strain T926) in the greenhouse in Bogor. All inoculated plants of eggplant died within 2 weeks. Bacterial wilt symptoms occurred on lower leaves of S. torvum plants tested without however causing any plant death. The presence of bacteria, serologically detected in roots of symptomless plants, suggested S. torvum to be tolerant to R. solanacearum. A sample of 10 accessions was shown to be highly resistant to an Italian isolate of F. oxysporum f. sp. Melongena, while the cultivated eggplant, line Tina used as positive control, died within 2 weeks after inoculation. The low levels of genetic diversity of Javanese accessions of S. torvum and their relatively homogeneous response in tolerance and resistance to bacterial and fungal wilts are discussed, respectively. [Copyright &y& Elsevier]