Phospholipase D inhibition by hexanal is associated with calcium signal transduction events in raspberry.

Raspberry (Rubus spp.) is an economically important crop with a restricted growing season and very limited fruit shelf-life due to its extreme tenderness. In order to prolong its shelf life, an aqueous composition containing hexanal as the key active ingredient (HC) was applied as a preharvest spray during fruit development. The effects of HC were assessed using physiological, biochemical and anatomical parameters on the treated fruits and compared with the effects of mock inoculation which lacked hexanal. Sugars and acidity did not show a significant change in response to HC treatment, while the pulling force (the tension required to detach the berry from the receptacle) significantly improved in the HC-treated fruits, compared to control. Scanning electron microscope (SEM) analysis revealed a high correlation between the presence of rigid epidermal hairs and a stronger degree of attachment between berries and their receptacle in the HC treated fruits. Further, electron micrographs also showed abnormal crystalline depositions on the epidermal drupelets of the treated berries. Energy Dispersive X-ray Spectroscopy (EDS) analysis showed those crystals to be largely composed of calcium. HC treatment also resulted in the reduction of transcript level of three phospholipase D genes, as well as altered expression pattern of five members of the annexin gene family, and four calmodulin-binding transcription activators. Quantification of PLD activity showed that hexanal inhibited PLD activity in treated berries. The potential crosstalk between hexanal, phospholipase D activity and calcium and this crosstalk's role in delaying fruit softening and in prolonging storage life of fruits shelf life is discussed.

Evaluation of nutritional profiles of starch and dry matter from early potato varieties and its estimated glycemic impact.

To identify healthier potatoes with respect to starch profiles, fourteen early varieties were evaluated for their dietary fiber, total starch, rapidly digestible (RDS), slowly digestible (SDS), and resistant (RS) starch for nutrition and with regard to estimated glycemic index (eGI) and glycemic load (eGL). While all these profiles were highly dependent on the potato variety, eleven out of fourteen varieties were classified as low GL foods (p<0.05). A strong positive correlation was observed with eGI and RDS (r=0.975-1.00, 0.96-1.00 and 0.962-0.997 for uncooked, cooked and retrograded varieties, respectively), whereas a strong negative correlation was observed between eGI and RS (r=-0.985 to -0.998, -0.96 to -1.00 and -0.983 to -0.999 for uncooked, cooked and retrograded varieties respectively, p<0.05). For the cultivars examined, the present study identified RDS and RS as major starch factors contributing to eGI.

Effect of seeding depth on seedling growth and dry matter partitioning in American ginseng.

Greenhouse and field experiments with American ginseng (Panax quinquefolius L.) stratified seed sown at depths of 10 to 100 mm were carried out to determine effects of seeding depth on seedling emergence, growth and development and to calculate optimum seeding depth. The time to 50% seedling emergence (E50) in the field increased linearly from 17 d at 20 mm seeding depth to 42.5 d at 80 mm. Seedling emergence and root weight (economic yield) at the end of the first year each increased quadratically with the increase of seeding depth. Maximum emergence and root yields were produced at sowing depths of 26.9 and 30.6 mm respectively. In a greenhouse pot experiment, increasing seeding depth from 10 to 100 mm increased partitioning of dry matter to leaves from 23.6% to 26.1%, to stems from 6.9% to 14.2%, and decreased dry matter to roots from 69.5% to 59.7%. Optimum seeding depth was 31.1 mm for a corresponding maximum root weight of 119.9 mg. A predictor equation [X (seeding depth, mm)=Y (seed weight, mg)/9.1+20.96] for seeding depth for ginseng, based on data for ten vegetable crops, their seed weights and suggested seeding depths, predicted a seeding depth of 28.3 mm for ginseng similar to that reported above for most pot and field experiments.

Genotype by environment interaction effects on starch content and digestibility in potato (Solanum tuberosum L.).

Biochemically, starch is composed of amylose and amylopectin but can also be defined by its digestibility rates within the human intestinal tract, i.e., rapidly digested (RDS), slowly digested (SDS), or resistant (RS). The relative ratio of these starch components is the main contributor to differences in the glycemic index (GI) of carbohydrate sources. This study evaluated the digestible starch profile of 12 potato genotypes comprising elite breeding lines and commercial varieties in six environments, with the optimal profile defined as low RDS and high SDS. Genotype by environment interaction (GEI) analysis found significant (p = 0.05) genotypic and environmental effects for all digestibility rate components; however, interaction effects were only significant for SDS. Optimal starch profiles were identified for two genotypes, CV96044-3 and Goldrush. The desirable starch profile in these potato cultivars can be exploited in breeding programs for the improvement of starch profile and other important characteristics such as high yields and disease resistance.

Micropropagation of African violet (Saintpaulia ionantha Wendl.).

Micropropagation is an important tool for rapid multiplication and the creation of genetic variability in African violets (Saintpaulia ionantha Wendl.). Successful in vitro propagation depends on the specific requirements and precise manipulation of various factors such as the type of explants used, physiological state of the mother plant, plant growth regulators in the culture medium, and growth conditions. Development of cost-effective protocols with a high rate of multiplication is a crucial requirement for commercial application of micropropagation. The current chapter describes an optimized protocol for micropropagation of African violets using leaf explants obtained from in vitro grown plants. In this process, plant regeneration occurs via both somatic embryogenesis and shoot organogenesis simultaneously in the explants induced with the growth regulator thidiazuron (TDZ; N-phenyl-N'-1,2,3-thidiazol-5-ylurea). The protocol is simple, rapid, and efficient for large-scale propagation of African violet and the dual routes of regeneration allow for multiple applications of the technology from simple clonal propagation to induction or selection of variants to the production of synthetic seeds.

Effect of preparation method on the glycaemic index of novel potato clones.

The purpose of this study was to investigate whether the effects of cooling and reheating on the glycaemic index (GI) of novel potato clones (selections) differed depending on selection and whether cooling altered starch absorption in vivo. We conducted 3 experiments using 4 novel potato clones in healthy subjects. Experiment 1: the GI of 4 selections each prepared in 3 ways (freshly boiled, cooled, or cooled and reheated) was measured in 2 groups of 10 subjects (each group tested 2 selections). Experiment 2 (n=10): two selections from Experiment 1 were re-tested one year later, by a different subject group. Experiment 3 (n=10): two selections from Experiment 1 were tested by subjects from Experiment 2 to assess the rate and extent of starch absorption using the second-meal effect and the breath hydrogen method, respectively. Experiment 1 demonstrated a selection×treatment interaction for GI (p=0.024); cooling reduced the GI of two selections by 40-50% (p<0.05) but reduced GI of the other 2 by only 8-10% (ns). Experiment 2 confirmed the selection×treatment interaction (p=0.018) seen in Experiment 1. Experiment 3: cooling reduced the GI by an average of 37% (p<0.05) but only increased starch malabsorption in vivo from 3% to 5% (p=0.021); there was no significant second-meal effect. It is concluded that the effect of cooling on the GI of potatoes may vary from 0-50% depending on selection. However, the mechanism for the effect is not clear: the 2% increase in starch malabsorption seen upon cooling potatoes was not nearly enough to account for the 37% reduction in GI.