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To induce virus resistance in tobacco and rice we constructed hairpin RNA expression system harbouring inverted repeat fragments of coat protein cDNA of Potato virus Y (PVY) or Rice stripe virus (RSV). These structures were driven by three promoters [cauliflower mosaic virus 35S (CaMV 35S), polyubiqutin gene of maize (Ubi), and Pharbitis nil leucine zipper gene (PNZIP)] which have different tissue-specific activity. PVY resistance ratios were 65.18, 24.33 and 83.54 % in transgenic tobacco plants harboring p35S-PVY, pUbi-PVY and pPNZIP-PVY. RSV resistance was 16.21, 28.61 and 29.33 % in transgenic rice plants harboring p35S-RSV, pUbi-RSV and pPNZIP-RSV. Northern blotting and GUS assay demonstrated that virus resistance levels were related to promoter activity. Therefore, choice of the more effective and tissue-specific promoter to reinforce transcription of hpRNAs will favour the cultivation of highly virusresistant transgenic plants.

Seed vigour is an important trait and is often used to evaluate seed quality. A rapid and accurate evaluation of seed vigour is very important for agricultural production. Ca 2+ is an important secondary messenger in plants, responding to various biotic and abiotic stimuli by Ca 2+ flux into cytoplasm. To the best of our knowledge, however, no report has been published about seed vigour and Ca 2+ influx. In this study, we used two hybrid maize (Zea mays L.) lines and their corresponding female parent lines as materials, and performed ageing and 'ageing + priming' treatments to obtain seeds with different vigour levels. After seeds were imbibed for 24 h, the intact seeds or embryos were used as materials for determining the Ca 2+ influx rate using non-invasive micro-test technique (NMT). Results showed that, with the intact embryos as materials, the Ca 2+ influx rate showed higher stability and higher values. Correlation analysis indicated that there was a significant, positive linear correlation between the shoot dry weight vigour index and Ca 2+ flux rate into embryo. The results demonstrated that the Ca 2+ influx rate can be used to evaluate the vigour levels of maize seeds.

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