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Daniel Rowley, Brent L. Black, Dan Drost, and Dillon Feuz

High tunnels have been used successfully in many areas of the world to extend the growing season for numerous crops. However, very little research has been conducted to evaluate the season extension benefits offered by high tunnels for small fruit crops in high-elevation growing areas such as the Intermountain West region of the United States. The use of high tunnels was investigated in North Logan, UT (lat. 41.766 N, elev. 1405 m, 119 freeze-free days) to extend the growing season for June-bearing strawberries. Growing systems included a fall-planted annual hill system and vertical growing systems in two different orientations. Optimum planting date for each system was determined by transplanting ‘Chandler’ plugs at 2-week intervals over 10 weeks. For the second year of the study, a field planting was also included. Over two seasons, the optimum planting dates were approximately the first week of September. The vertical systems were more susceptible to winter injury likely resulting from the temperature extremes in the root zone. Where winter injury was prevented, the vertical systems had higher yields per tunnel area than the in-ground system, but yield increases did not compensate for higher construction and management costs. The production window for the in-ground high tunnel planting was ≈4 weeks earlier than the field-grown plants and increased profitability by $13/m2 of tunnel area.

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Daniel Rowley, Brent L. Black, Dan Drost, and Dillon Feuz

Small-scale fruit and vegetable growers increasingly use high tunnels to expand production windows and exploit demand for local produce. Day-neutral cultivars, high tunnels, low tunnels, and targeted heating were investigated in North Logan, UT (lat. 41.766° N, 1405 m elevation, 119 freeze-free days) to extend the availability of local strawberries. Day-neutral cultivars Albion, Evie 2, Seascape, and Tribute were spring-planted in an annual hill system both inside and outside of high tunnels. Within the high tunnels, low tunnels and targeted root zone heating were tested in replicated plots. During the summer months, plastic was removed from the high tunnels and replaced with shadecloth. Treatments were evaluated for yields, fruit size, and production season. Fruit production in the tunnels began in late May and continued sporadically until December. Combinations of high and low tunnels provided more hours of optimal growing conditions than high tunnels alone, but managing the combination to maintain optimum temperatures proved difficult with temperatures often exceeding the optimum for strawberry. Targeted root zone heating efficiently increased root and canopy temperatures, preventing flower bud damage during extreme cold events, but did not significantly improve total season yields. Of the cultivars tested, ‘Evie 2’ and ‘Seascape’ had the most consistent yields and acceptable fruit size. Economic analysis indicated that growing spring-planted day-neutral strawberries in high tunnels was marginally profitable, whereas field production at this location would be a money-losing enterprise.

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Nathan C. Phillips, Steven R. Larson, and Daniel T. Drost

Three wild onion species native to the intermountain west in the United States—Allium acuminatum, A. brandegei, and A. passeyi—show horticultural potential, but little is known about patterns of genetic diversity among localized populations and geographical regions. We examined amplified fragment length polymorphisms (AFLP) within and among five Allium acuminatum, four A. brandegei, and three A. passeyi collection sites in Utah. These three congeners with contrasting abundance and distribution patterns provide an opportunity to investigate the role of geographic distance, altitude, and rarity in patterns of genetic divergence. The collection sites were selected along an altitudinal gradient to reflect ecogeographic variation. Individual plants from each of the 12 sites were genotyped using six AFLP primer combinations detecting DNA variation within and among all three species. Genetic differences between species were high enough to render comparisons among species impractical, so each species was analyzed separately for differences between populations and variability within populations. Similarity coefficients were significantly greater within collection sites versus among collection sites indicating divergence between populations. Within-population genetic diversity was not correlated with elevation for any of the three species. Analysis of molecular variance revealed that 66% (A. acuminatum), 83% (A. passeyi), and 64% (A. brandegei) of observed variation is found within populations. Genetic divergence among populations (ФST) was higher in the widely distributed species, suggesting that interpopulation gene flow may be negatively correlated with range size. Allium acuminatum and A. brandegei individuals cluster into groups corresponding strictly to collection sites based on neighbor-joining analysis of the total number of DNA polymorphisms between individual plants. Allium passeyi populations, however, had less overall genetic variation between populations. Genetic isolation by distance appeared responsible for much of the variability among populations, although there was one notable exception showing significant differences between two geographically close populations in A. acuminatum.

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Nathan C. Phillips, Daniel T. Drost, Bill Varga, Leila Shultz, and Susan E. Meyer

Seed germination timing strategies and seedling growth characteristics in wild populations have evolved in response to their life history, ecology, and habitat. In this study, we examined the ecophysiological aspects of seed germination and growth in three Allium species native to the Intermountain West (A. acuminatum, A. brandegei, and A. passeyi). Three populations of each species were studied along an elevation gradient resulting in low, mid, and high elevation sites for each species. We investigated seed dormancy patterns within and among species and their relation to habitat. Seeds collected at the study sites were subjected to cold (3 °C) moist stratification in low light to simulate the natural winter environment under snow. Stratification periods ranged from 0 to 24 weeks. After stratification, seeds were placed in lighted growth chambers at 8 °C to simulate the natural spring environment. Germination was observed for 4 weeks. Germinated seeds were then grown at either 12 °C or 16 °C until leaf senescence. Destructive sampling occurred at 2, 4, and 8 weeks. Bulb mass and water content were also assessed after leaf senescence. In the germination experiment, all species responded favorably to cold moist stratification, suggesting physiological seed dormancy. Germination percentages among species varied greatly with 98% germination in A. acuminatum, but only 33% in A. brandegei. Seedling survival and growth varied among species and in response to growing temperature. Observed patterns in seed germination and growth are typical of survival strategies in other spring ephemerals. Seed dormancy traits and seedling growth characteristics in these species have evolved to allow optimal success for their specific habitat.

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Tiffany L. Maughan, Kynda R. Curtis, Brent L. Black, and Daniel T. Drost

Strawberry production in the U.S. Intermountain West is limited by harsh climatic conditions and competition from domestic producers and imports. Using season extension methods to combat climatic conditions may be effective but generally increases production costs. This study evaluates the economic returns to implementing high tunnels, low tunnels, and in-ground supplemental heating to strawberry production (Seascape and Chandler cultivars) in northern Utah. The high tunnel provided a net return of $1,943.57 or $15,548.56 per hectare assuming eight high tunnels per hectare. The addition of low tunnels within the high tunnel led to a positive increase in net returns for ‘Seascape’ but not for ‘Chandler’ production. Supplemental in-ground heating increased net returns by up to 50% for both cultivars, primarily as a result of higher pre-season yield and market pricing. Study results find that season extension technologies can successfully increase net returns to strawberry production through early and increased yields, when strawberries are sold primarily through local direct markets.