A forcing solution containing 200 mg 8-hydroxyquinoline citrate per liter and 2% sucrose has been demonstrated to extend the season for obtaining softwood growth suitable for use as explants in micropropagation (Yang & Read 1989). Forcing dormant woody stems in the off-season in this fashion also enhances the macropropagation of woody plant species by providing softwood outgrowth that can be rooted as softwood cuttings. GA3, IBA, IAA and NAA were incorporated into softwood growth which was later used as cuttings for rooting by adding plant growth regulators at various concentrations to the forcing solution. GA3 incorporated into the forcing solution hastened bud break, increased shoot elongation, but inhibited rooting of softwood cuttings taken from stems forced in this manner. IBA, IAA and NAA in the forcing solution exhibited typical auxin effects on rooting of cuttings by increasing root number per cutting and root elongation. In order to expedite macropropagation of woody plants, GA3 and IBA were added SEQUENTIALLY to the forcing solution. Addition of IBA to fresh forcing solution following initial use of GA3 in the forcing solution counteracted the negative effects of GA3 and stimulated rooting. This protocol is proposed as a method to assist propagation in rooting difficult species by softwood cuttings in the off-season.
Barry Duncil and Robert Geneve
Wild rye (Elymus) contains several species of cool season grasses that are important components of forest and woodland ecosystems. Little specific information is known about seed dormancy in wild rye species, but cool season grasses generally display endogenous, non-deep physiological dormancy that would normally be satisfied by moist chilling during winter to permit early spring germination. However, few studies have documented the effect of extended chilling stratification on dormancy release in cool season grasses. Therefore, the objective of this study was to document the dormancy condition of representative wild rye species and to observe the impact of chilling stratification on dormancy release. Three species of wild rye (E. virginicus, E. macgregorii, and E. villosus) were selected based on their taxonomic and ecological relationships. All species showed conditional dormancy with respect to germination temperature. At 15 °C, E. virginicus, E. macgregorii, and E. villosus germinated at 75%, 81%, and 40%, respectively, compared to 5%, 3%, and 12% for each species at 20 and 25 °C. Chilling stratification at 10 °C improved germination compared to non-stratified seeds to 95% and 94% for E. m acgregorii and E. villosus, but had no effect or reduced germination in E. virginicus. Stratification at 5 °C was not as effective as 10 °C for dormancy release and appeared to cause chilling injury in E. virginicus and E. macgregorii. The data suggest that these wild rye species express a form of conditional endogenous, non-deep physiological dormancy that is most pronounced when seeds are germinated at non-optimal temperatures.
James Hill Craddock, R.J. Sauve, S.E. Schlarbaum, J. Skinner, R.N. Trigiano, M.T. Windham, and W.T. Witte
Hand pollinations and honey bees were used to cross Cornus florida cultivars in a series of experiments investigating dogwood pollination biology from a breeding viewpoint and testing the use of insects (domestic honey bees and ladybug beetles as pollinators in dogwood breeding. Experiments were conducted to study possible incompatibility between dogwood cultivars and to determine if self-compatibility and self-fertility occur in Cornus florida. Since 1993, ≈200 seedlings have been produced by hand and insect-mediated pollinations. Honey bees can be used in dogwood breeding. Trees cross pollinated by ladybeetles had lower fruit set than trees cross pollinated by honey bees. Greenhouse forcing to accelerate anthesis and cold storage to delay the onset of bloom of container-grown trees can extend the dogwood breeding season effectively.
Heather D. Bryant, Mark G. Hutton, David T. Handley, and Mary Ellen Camire
Some Maine tomato growers use unheated greenhouses or high tunnels to extend the short growing season. But, what varieties should growers choose? The objective of this trial was to test varieties of greenhouse and open field tomatoes to identify the best performers in high tunnels in terms of yield, quality, disease, and taste. Results showed that both open field and greenhouse varieties produced similar and acceptable yields of high quality marketable fruit. Open field varieties showed more disease than greenhouse varieties. There were some significant differences between individual varieties. Betterboy scored highest in sensory analysis, but lowest in yield/quality. Brilliante scored poorly on marketable yields, but well in terms of premium yields, quality, disease and taste. It may be well suited for direct marketing to repeat customers (e.g., farmers' markets). For commercial production Jet Star, Brilliante, Cobra, and First Lady II appear to be good choices based on overall scores.
William Reid and Kenneth L. Hunt
More than 93% of pecans [Carya illinoinensis (Wangenh.) K. Koch] produced in the United States are grown in the southeastern and southwestern states. However, the native range of the pecan tree extends northward into Kansas, Missouri, and Illinois. In these northern states, commercial pecan production is expanding as additional acres of native trees are brought under cultivation and orchards of short-season, cold-hardy cultivars are established. Native nut production dominates the northern pecan industry accounting for over 95% of nuts produced in the region. Cultural practices for native pecans have been developed for northern groves that feature low inputs and good yields. Pecan cultivars adapted to the north ripen their fruit in a climate that provides 155 to 200 frost-free days. Few generalizations can be made about northern cultivars. The nuts produced by these cultivars vary in size from small [4 g (0.14 oz)] to medium [8 g (0.28 oz)] with shelling percentages ranging from 44% to 59%.
Marvin P. Pritts, Robert W. Langhans, Thomas H. Whitlow, Mary Jo Kelly, and Aimee Roberts
Floricane-fruiting (summer-bearing) raspberries (Rubus idaeus L.) were grown outdoors in pots in upstate New York until mid-December when the chilling requirement was fulfilled. They were moved into a greenhouse and placed at a density that is three times higher than field planting. Bumble bees (Bombus impatiens Cresson) were introduced at flowering for pollination. Fruiting occurred from mid-February through mid-April, a time when the retail price for raspberries is between $3.00 and $6.00 for a half pint (180 g). Fruit quality was high, and individual 2-year-old plants averaged 11 half pints (2 kg) of marketable fruit. These yields and retail prices are equivalent to 19,000 lb and $142,000 per acre (21 t, $350,000 per ha). Raspberry production during winter allows growers to dramatically extend the harvest season and to produce a high-value crop at a time when greenhouses often are empty.
Douglas V. Shaw
The extended production season of strawberries raised in mediterranean environments depends on plant development that occurs during the winter months. Seedling genotypes from 20 bi-parental crosses and their nine parent genotypes were fully vernalized and grown at 11, 14, and 17C, to test for adaptation to growth at minimal temperatures. Genetic variance parameters were estimated and tests for genetic x temperature interactions were conducted for five vegetative growth traits. Highly significant (P < 0.01) genetic effects were detected for all traits, and broad-sense heritability estimates ranged from 0.09 to 0.41. None of the genetic x temperature interactions were significant for seedling genotypes, and interactions were significant only for leaf dry weights for parental genotypes. These results indicate a genetic basis for variable vegetative growth rates, but provide no evidence for specific adaptation to growth at low temperatures.
Aref A. Abdul-Baki, J.R. Teasdale, R. Korcak, D. Chitwood, and R Huettle
Fresh-market tomatoes (Lycopersicon esculentum Mill) cvs. Sunny and Sunbeam were grown in bare soil (BS), Horto paper (HP), black polyethylene (BP), hairy vetch (HV), crimson clover (CC), and hairy vetch plus rye (HVR) mulches. Yields were highest in HV (85.8 t·ha–1), followed by HVR 69.3 t·ha–1) and CC (65.7 t·ha–1), and averaged 47% above BP for the 3-year period. A 5- to 9-day earliness was exhibited by BP over other treatments. Fruit weight was significantly higher in all three organic mulch treatments than in the other three treatments. Mulch biomass was highest in HVR (5.91 t·ha–1), whereas N fixation was highest in HV (188 kg·ha–1). Tomato harvest was extended by the HV treatment over the BP treatment by 3 to 4 weeks, during which tomato prices were higher than those in early or mid-season.
Sylvie Jenni and Katrine A. Stewart
Quebec vegetable growers are increasingly using agricultural plastics (plasticulture) not only for gains in crop yield, earliness, and quality, but also for weed control and water and fertilizer conservation. Curcubitaceae include heat-loving crops that respond well to plasticulture. Melons are among the most responsive of all crops because they are sensitive to both low soil and air temperatures and to wind, but are very tolerant of high temperatures. The objective of this project was to develop a bioeconomic model that will predict the yield and timing of a melon crop under a number of mulch/tunnel combinations, evaluate the profitability of each production regime, and establish the optimal combinations that will maximize profit and continuity of supply over an extended growing season. A compartment model representing state, rate, and driving variables will be presented.
John R. Clark
Eastern U.S. blackberries (Rubus subgenus Rubus) have advanced in recent years in production and quality of cultivar choices. Mainly a pick-your-own and local sales item of the early 1990s and before, the increased presence of blackberries in retail grocery stores in the last 10 years has broadened the market for this small fruit. Cultivars that can be shipped and have extended shelf life have been the cornerstone of this expansion. Also, off-season production in Mexico has provided fruit for retail marketing during most months of the year. Further advances in production, marketing, and consumption can be achieved with the continuation of improved cultivar development and expansion of production technology.