Greenhouse grown `Lawspur Rome'/M.111 trained to single shoots were given the following shade (73%) treatments: 1) sun-all-day (control), 2) shade in the morning (am-shade), 3) shade in the afternoon (pm-shade) and 4) shade-all-day. All shade treatments increased shoot length and decreased dry weight/leaf area (DW/LA). Shade-all-day increased leaf no., LA/leaf and shoot dia. DW partitioning to leaves in shade-all-day was 19% greater than control and to roots was 34% less than control. Pn of am-shade did not increase in the afternoon when PFD was maximal. Saturated net photosynthesis (Pn) was 72% of control in am-shade, 84% of control in pm-shade and 62% in shade-all-day. Shade reduced Pn by 40% of control.
Renae E. Moran and Curt Rom.
Ken Kupperman and Curt R. Rom
The effect of soil preplant strategies winter solarization and methyl bromide fumigation were compared to a non-treated control on apple tree growth. Treatments were applied in the fall after removal of an existing orchard with spring planting of 'Jonee' and 'Smoothee Golden Delicious' on M.26 EMLA rootstock. Soil fumigation significantly increased shoot length in first year, trunk cross-sectional area increase during two seasons, and bloom and set in second year. The control and winter solarization treatments were similar in all responses. Foliar Mn concentrations were significantly lower with fumigated trees in second years compared to other two treatments, which were similar.
Robert D. Bourne and Curt Rom
Several trials were conducted to compare standard and potential peach rootstocks. The NC-140 trial, with 'Redhaven' as the scion, included 'Halford', 'Siberian-C', 'Bailey', 'GF-677', 'GF-655.2', 'Damas', 'Citation', 'Lovell' and 'GF-43' rootstocks. All trees with 'Citation' as the rootstock died in the first three years. while 'CF-43' and 'Siberian-C' had low survivability and productivity. 'Damas' and 'GF-43' suckered profusely. 'Lovell' trees bloomed an average of one-to-three days later than all other entries. 'Halford'. 'GF-677', 'Bailey' and 'Lovell' had the highest yields. A trial comparing 'Loring' own-root and on 'Tennessee Natural' resulted in similar yields among stocks, but larger fruit and tree size with the own-root trees. 'Redskin' own-root and on 'Lovell' also resulted in similar yields among stocks, and larger tree and fruit size with own-root trees. A trial using the processing peach selection A-219 as the scion on `S-37' 'Chum Li Tao', AR-78118, 'Yarbrough Cling' and 'Lovell' resulted in highest yields and yield efficiency with 'Yarbrough Cling', 'Lovell' and 'S-37' rootstocks.
Vikramjit S. Bajwa* and Curt Rom
Osmotic agents used to prevent apple pollen grain germination were studied in vitro by applying 10 μL of solutions to germinating apple pollen on germinating and growth media. Seven concentrations (0%, 0.25%, 0.5%, 1%, 2%, 5% and 10%) of the solution were prepared for each chemical and the characteristics of pH, EC, and osmotic potential were measured. Apple pollen was dispersed onto the media in petri dishes. Micro drops of solution were then applied to marked areas. Dishes were then placed in germination cabinets at 25 °C. Cumulative percentage pollen germination was calculated 4, 8, 12, and 24 h after treatment by microscopic observation. Generally, the cumulative percentage pollen germination decreased asymptotically with increasing chemical concentration. The most effective chemicals for restricting pollen germination and growth were CuSO4 (0.25%), CH3 COOH (0.25%), CaCl2 (10%), K2 S2 O5 (0.25%), Methyl Jasmonate (2%). The effect of these chemicals has also been tested on pistil viability both in vitro and on excised limbs.
Vikramjit Bajwa and Curt R. Rom
Alternate bloom thinners are needed for apple are needed to replace compounds which can no longer be used or have production system limitations. The effects of 24 chemicals selected as osmotic agents, organic acids, oils, essential oils, or potential metabolic agents and their properties of pH, electrical potential (EP) and water potential were tested in vitro on `Gala' apple pollen germination, tube growth and pistil damage. Solution concentrations of 0%, 0.25%, 0.5%, 1%, 2%, 5%, and 10% were prepared and solution pH, EP, and water potential measured. To test affects on germination, pollen was placed on agar germination media in petri dishes and then treated with 10: l of chemical solution. Percentage pollen germination and tube growth was calculated 4, 12, and 24 h after treatment. Excised pistils from forced flowers were placed on glass filter papers saturated with chemical solution. Pistil damage was visually, subjectively rated for damage indicated by discoloration 24 h after treatment. Effects of solution pH, EP and water potential on pollen germination, tube growth and pistil damage was significant with pH less than ∂4.0 or greater than ∂10.0, EP > 200mv, or water potential less than ∼4.0MPa inhibited pollen germination, growth, and killed pistils. Several chemical had apparent metabolic effects beyond the chemical effects mentioned above. In vitro tests were correlated to in vivo field tests in other studies indicating the use of pollen and pistil in vitro as a useful model for screening potential alternative thinning agents.
Curt R. Rom and Bruce Barritt
The role of spur leaves in bud and fruit development on two spur-type `Delicious' apple strains (Malus domestica Borkh.) and factors affecting spur development were studied. Reducing spur leaf area on vegetative spurs in August reduced the number of spurs that flowered the following year but did not affect flower size. On spurs that did flower, leaf area reduction the previous year did not influence leaf number or area, but the bourse shoot leaf area was reduced. Spur bud diameter, leaf area, size, specific leaf weight (SLW), and leaf dry weight were larger on 2-year-old vegetative spurs than on 1- or 3-year-old spurs. Within each age section of a limb, spur leaf number, area, size, SLW, and bud diameter decreased from the apical to basal positions on the limb. Flower number did not vary within a limb section, but fruit set was lower on the most apical and basal spurs compared to midshoot spurs. Fruit size was largest at the apical end of each limb section and was smallest at basal positions. These relationships were not affected by strain, tree age, or orchard location. Summer pruning at 30 days after bloom tended to increase leaf number, area, size, and spur length compared to unpruned trees or pruning later in the season but did not influence spur bud diameter.
Kristen Harper and Curt R. Rom
Since the passage of the Organic Foods Production Act in 1990, certified organic produce has begun to make a large impact on national markets. However, USDA statistics indicate that many states in the southern region have considerably reduced certified organic acreage when compared to other regions in the United States. The absence of organic acreage may perhaps originate with a lack of training and educational materials provided to producers due to unanticipated growth of organic markets. A thorough review of all Arkansas Cooperative Extension Service (ACES) materials, such as bulletins, publications, and workshops over the past 10 years, would reveal what information has been provided to producers on certified organic production. This review of ACES materials defines the existing groundwork on which ACES could construct future organic publications and outreach programs in order to sustain and stimulate organic farming within the state.
Curt R. Rom*, Zimian Niu, and Vikramjit Bajwa
A strategy of chemical crop load control has been to use chemical desiccants to prevent fertilization and cause fruitlet drop. However, little is known of the solution characteristics that reduce pollen viability, inhibit pollen germination and growth, and cause pistil damage. This project was established to determine the solution characteristics effecting those results. Apple pollen was dispersed on germination media mixed with PEG (MW 10,000) to attain osmotic tensions from 0 to -5.0 MPa to evaluate effect on pollen germination and growth. Similarly, apple pollen was dispersed on germination adjusted to a range of pH from 2.3 to 12.0 with acids and NaOH. Excised apple pistils were place on filter paper supports saturated with solutions with osmotic tension adjusted by PEG in the range of 0 to -5.0 M Pa, and pH from 3.0 to 12.0. Solutions of osmotic tension in the range of 0 to -5.0 M Pa were applied by brush to intact pistils on apple flowers in a greenhouse and under field conditions. Pollen germination decreased with increasing osmotic tension and no pollen germinated at tensions greater than 4.0. Pistils, either excised or intact, had significant desiccation and death when treated with solution osmotic tensions greater than 4.0. Fruit set of individual spurs of the cvs Jonagold, Gala, and Arkansas Black were highly related to pistil survival 48 h after treatment with PEG. When solution osmotic potential exceeded 4.0, fruit set was reduced by more than 80%. Pollen germination was reduced by more than 50% at solution pH below or equal to 4.0 and greater than 10.0 and completely inhibited at solution pH below or equal to 3.0 and greater than 11.0. Similar results were observed for excised pistil and intact viability.
Ray A. Allen and Curt R. Rom
Light distribution in two cultivars on three dwarfing rootstocks in three high-density apple tree training systems was measured in the sixth leaf beginning at full bloom and continuing through the season. Training system had a significant effect on light penetration into the lowest point of the canopy (measured at 0.5 m), with the slender spindle being significantly darker than either the central leader or the vertical axis, although all three systems were below the threshold value of 30% full sun (FS) needed to maintain productivity for most of the season. Cultivar had no significant effect; however, trees of both `Jonagold' and `Empire' fell below 20% FS early in the season and remained there until late in the season. Rootstock had the greatest effect, with trees on M9 and M26 being significantly darker in the lower canopy than trees on Mark. Trees on M26 and M9 fell below 10% FS early in the season and remained there, while trees on Mark never fell below 20% FS.
John R. Clark and Curt R. Rom
Small fruit production in the southern United States has been impacted greatly by fruit breeders this century. This workshop, co-sponsored by the American Pomological Society, includes presentations from individuals who have contributed collectively over 150 years to small fruit and grape breeding. James N. Moore has conducted breeding at the University of Arkansas, developing 30 cultivars. His presentation on brambles outlines achievements and future opportunities for improvement. Arlen Draper has been involved with the development of 61 small fruit cultivars while working with the USDA-ARS with an emphasis on blueberry. His presentation focuses on blueberry breeding and provides insights into the future of new blueberry cultivar developments. Gene Galletta has conducted small fruit breeding at North Carolina State University and USDA-ARS and has been involved with the development of 50 cultivars. His presentation reflects on the history of strawberry breeding in the South and the challenges that lie ahead. Ron Lane has served as a fruit breeder and horticulturist at the University of Georgia Experiment Station at Griffin and his work has emphasized the development of muscadine grape cultivars. The past and future of muscadine and bunch grape breeding is discussed in his paper. Articles from all authors in this workshop will be published in Fruit Varieties Journal in 1997.