J. Alan Sullivan

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.

Genotype by environment interaction effect on yield and quality of potatoes

Colour is an important character in the processing of potatoes for French fries. French fry colour is closely associated with sugar content in the tuber. This study examines the stability of yield, sugar content and French fry colour for eight potato cultivars and advanced selections in four environments. Stability was determined using three approaches based on the Eberhart-Russell, Tai and GGE Biplot analyses. The GGE Biplot analysis provided a better characterization of stability than the other two analyses. The most stable and best performing genotypes for both French fry colour and total sugars were Russet Burbank and Umatilla Russet. Cal White had high yield and yield stability but had average stability for poor (dark) French fry colour. The GGE biplot analysis was able to identify mega-environments and those environments which optimized differentiation between genotypes. Both factors are important for the optimization of resources for testing new genotypes. Stability for quality factors in potato ca...

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.

Early generation performance of Fragaria species hybrids in crosses with cultivated strawberry

Yield (i.e., fruit number and size) and yield component measurements were collected and destructive growth analysis carried out on lower-ploidy Fragaria species, synthetic octoploids (SO), F1 (SO × cultivar), OC1 (F1 × cultivar) hybrids and cultivars. Plants were grown in two field trials, at the Elora Research Station, Ontario, and at the Wye Research and Education Centre, Queenstown, Maryland, and in one greenhouse trial in Guelph, Ontario. Total plant dry weight (PDW) was highly variable for the species, but the higher vegetative vigour of the SOs compared with mid-parent values suggested a heterotic effect. The shade adapted species (e.g., F. moschata Duch. and F. nubicola) had greater PDWs than the sun adapted species. Yields of the species, SOs and F1 hybrids were low; however, flower number was higher compared with cultivars. The first outcross with F1s and cultivars resulted in a sixfold increase in yield attributed to both increased fruit size and fruit number. Three of the four OC1 hybrids had y...

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.

Performance of five haskap (Lonicera caerulea L.) cultivars and the effect of hexanal on postharvest quality

Abstract: Growers are challenged to provide premium, ripe haskap fruit to market while limiting the negative attributes associated with over-ripening. Hexanal is an inhibitor of phospholipase D, an enzyme involved in membrane degradation, and has shown promise in extending the longevity of fruit. This study investigated the performance of a hexanal-based preharvest spray for enhancing the quality and shelf life of haskap fruit, an emerging crop in Canada. At two locations in 2015, 2016, and 2017, five cultivars were sprayed with a control treatment or a 0.02% hexanal formulation at 2–3 wk before harvest. Fruit was stored at 4 °C and assessed for quality at successive times. Although inconsistent, results suggest a hexanal spray may impart a small benefit to the postharvest quality of haskap fruit. Secondary objectives included describing important agronomic characteristics of haskap and assessing the potential of a hexanal preharvest spray for enhancing fruit retention. Hexanal did not reduce fruit drop and had no effect on quality at harvest. Fruit contained high levels of soluble solids and titratable acids, were very dark in colour, and did not degrade in quality as rapidly as softer fruit crops such as strawberry or raspberry.

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.