Steve Sykes

Contrast in chloride exclusion between two grapevine genotypes and its variation in their hybrid progeny

Potted grapevines of 140 Ruggeri (Vitis berlandieri × Vitis rupestris), a good Cl− excluder, and K 51-40 (Vitis champinii × Vitis riparia ‘Gloire’), a poor Cl− excluder, and of a family obtained by crossing the two genotypes, were used to examine the inheritance of Cl− exclusion. Rooted leaves were then used to further investigate the mechanism for Cl− exclusion in 140 Ruggeri. In both a potting mix trial (plants watered with 50 mM Cl−) and a solution culture trial (plants grown in 25 mM Cl−), the variation in Cl− accumulation was continuous, indicating multiple rather than single gene control for Cl− exclusion between hybrids within the family. Upper limits of 42% and 35% of the phenotypic variation in Cl− concentration could be attributed to heritable sources in the potting mix and solution culture trials, respectively. Chloride transport in roots of rooted leaves of both genotypes appeared to be via the symplastic pathway, since addition of 8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS), an apoplastic tracer, revealed no obvious PTS fluorescence in the laminae of either genotype, despite significant accumulation of Cl− in laminae of K 51-40 during the PTS uptake period. There was no significant difference in either unidirectional 36Cl− flux (10 min) or 36Cl− uptake (3 h) into roots of rooted leaves exposed to 5, 10, or 25 mM Cl−. However, the percentage of 36Cl− transported to the lamina (3 h) was significantly lower in 140 Ruggeri than in K 51-40, supporting reduced Cl− loading into xylem and implicating the root stele in the Cl− exclusion mechanism.

Improved in ovulo embryo culture for stenospermocarpic grapes (Vitis vinifera L.)

In ovulo embryo rescue techniques have been used to recover new hybrids from seedless × seedless grape crosses. This study was conducted to increase efficiency by investigating effects of genotype, medium, and ovule removal age on ovule elongation, embryo recovery, growth, and plantlet formation. Ovules from self-pollinated berries of seedless varieties Sunmuscat, Merbein Seedless, and Marroo Seedless were cultured at 30, 43, 60, and 70 days after flowering (DAF) in a range of media, some of which were supplemented with gibberellic acid (GA3) and indole-3-acetic acid (IAA). The effect of activated charcoal (AC) in media on rescued embryos was also investigated. Ovules exhibited continuous growth in vivo and in vitro. The most vigorous growth was observed for ovules cultured at 30 and 43 DAF, but more embryos were recovered from ovules cultured at 60 and 70 DAF. Ovule growth and embryo production in vitro were improved in Bouquet and Davis (BD) and Nitsch and Nitsch (NN) media. Supplementation with GA3 increased embryo recovery rates. Highest embryo recovery rates were 18.1%, 9.6%, and 12.2% for Sunmuscat, Merbein Seedless, and Marroo Seedless, respectively, when ovules were excised and cultured at 60 or 70 DAF in either BD or NN media. In vitro embryo survival and plantlet formation were higher for torpedo-shaped embryos, and improved greatly in 6-benzyladenine (BA)-supplemented woody plant (WP) medium containing 0.3% AC. Embryo recovery was improved by excising and culturing ovules at 60 DAF in BD or NN media and then by transferring embryos to WP medium supplemented with BA and AC.

Pollen fertility and berry setting behaviour of the grape variety Carina

Carina is a significant grape variety grown in Australia to produce dried currants. Its yield and fruit quality are restricted by pollination; however, this can be improved by the judicious use of hormone-based setting sprays. Male fertility and seedless berry set in Carina were investigated by examining pollen viability, the effect of self- and cross-pollination on berry set and in ovulo embryo recovery in comparison with two pollen sterile varieties, Hunisa and Kishmishi. Carina pollen failed to germinate in vitro and gave poor berry set when used to pollinate Hunisa and Kishmishi. Percentage berry set in Carina was unaffected by pollination treatments, but cross-pollination increased berry size. Larger seed traces (>1.2 mm in length) were present in most cross-pollinated Carina berries and their size and number were correlated positively with berry size. In ovulo embryo recovery rates ranged from 19.7 to 49.0% and 6.8 to 13.6% for cross-pollinated combinations of Carina when ovules were cultured at 50 and 75 days after pollination, respectively. In contrast, embryo recovery was zero from self-pollinated ovules. The results indicated that Carina produces sterile or non-functional pollen and is capable of setting seedless fruits through either parthenocarpy and/or stenospermocarpy.