Genotype and environmental effects on ginsenoside content among eight wild populations of American ginseng (Panax quinquefolium) were investigated. Root concentrations of six ginsenosides were determined at the time of collection of plants from the wild (T0) and 2 years (T2) after transplanting roots from each of the eight populations to each of two different forest garden locations. Both location and population had significant effects on root and shoot growth. Overall, ginsenoside Rb1 was most abundant, followed by Rg1 and Re. Concentrations of Rg1 and Re were inversely related among and within populations. The relative ranking of populations differed depending upon the particular ginsenoside and sampling time. The relative importance of genotype and environment was not the same for all ginsenosides. Ginsenoside Re was influenced by population but not location, whereas Rb1, Rc, and Rb2 were influenced only by location (environment), while Rg1 and Rd were influenced by both. Ginsenoside levels were consistently lower, but growth was consistently higher at the more intensively managed garden location.

SummaryWhile various signalling networks regulate plant responses to heat stress, the mechanisms regulating and unifying these diverse biological processes are largely unknown. Our previous studies indicate that the Arabidopsis monothiol glutaredoxin, AtGRXS17, is crucial for temperature-dependent postembryonic growth in Arabidopsis. In the present study, we further demonstrate that AtGRXS17 has conserved functions in anti-oxidative stress and thermotolerance in both yeast and plants. In yeast, AtGRXS17 co-localized with yeast ScGrx3 in the nucleus and suppressed the sensitivity of yeast grx3grx4 double-mutant cells to oxidative stress and heat shock. In plants, GFP-AtGRXS17 fusion proteins initially localized in the cytoplasm and the nuclear envelope but migrated to the nucleus during heat stress. Ectopic expression of AtGRXS17 in tomato plants minimized photo-oxidation of chlorophyll and reduced oxidative damage of cell membrane systems under heat stress. This enhanced thermotolerance correlated with increased catalase (CAT) enzyme activity and reduced H 2 O 2 accumulation in AtGRXS17-expressing tomatoes. Furthermore, during heat stress, expression of the heat shock transcription factor (HSF) and heat shock protein (HSP) genes was up-regulated in AtGRXS17-expressing transgenic plants compared with wild-type controls. Thus, these findings suggest a specific protective role of a redox protein against temperature stress and provide a genetic engineering strategy to improve crop thermotolerance.

Vegetables represent an attractive means of providing increased calcium nutrition to the public. In this study, it was demonstrated that lettuce expressing the deregulated Arabidopsis H(+)/Ca(2+) transporter sCAX1 (cation exchanger 1) contained 25%-32% more calcium than controls. These biofortified lettuce lines were fertile and demonstrated robust growth in glasshouse growth conditions. Using a panel of highly trained descriptive panellists, biofortified lettuce plants were evaluated and no significant differences were detected in flavour, bitterness or crispness when compared with controls. Sensory analysis studies are critical if claims are to be made regarding the efficacy of biofortified foods, and may be an important component in the public acceptance of genetically modified foods.

Haploid/doubled haploid (DH) technology can aid plant breeding programs by accelerating production of homozygous lines, provided enough viable DH progeny can be obtained from diverse haploid genotypes. In cases where there is a low frequency of spontaneous doubling, chromosome doubling procedures are required to achieve fecundity. We produced 63 parthenogenetic melon plantlets via pollination with c-irradiated pollen, cloned them by nodal cuttings, and tested the effects of in vitro and in vivo colchicine treatment on survival, ploidy, pollen production, and fruit recovery. The most effective procedure was in vitro exposure of 3 cm shoot tip explants to 500 mg/l colchicine for 3 h. This treatment gave 83% survival of explants and 26% conversion to diploidy. Fruit recovery rate was 60% among plants with good pollen production. In vivo exposure of the tops of young plants to 5000 mg/l for 2 and 4 h yielded some fruits but also resulted in less survival and more morphological abnormalities. Strategies for recovery of progeny from parthenogenetic melon plants are recommended. To our knowledge, this study represents the first comprehensive study of recovery of fruits and viable seeds from parthenogenetic melon plants.

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