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Flower bud development was studied in `Cherokee', `Boysen', and `Marion' blackberries (Rubus subgenus Rubus Watson). In `Cherokee' (erect type), the transition to reproductive development in buds on the branch canes occurred during September in Arkansas and Oregon. Transitions of buds in the axils of the most basal nodes (proximal to the main cane) and the most distal nodes lagged behind buds in the midsection (about nodes 6 to 10). Along the midsection of branch canes, the buds developed uniformly. In buds of `Boysen' and `Marion' (trailing type), the transition to reproductive development occurred in October and sepal primordia were observed in most buds examined by November. Progression of floral bud development continued into January, but at a slower rate than in autumn. Buds on the main canes (>3 m long) of `Boysen' and `Marion' remained at a more advanced stage of flower bud differentiation than buds on the basal branch canes. In both cultivars, buds from the middle one-third section, and sometimes buds from the bottom one-third section, tended to be more advanced than those buds in the top one-third section during much of the sampling period. The results suggest that rate and patterns of flower bud development vary among cultivars grown in different locations. However, the pattern of flower bud development was not in a basipetal fashion on main or branch canes.
Transition to reproductive development and subsequent development of floral primordia (e.g., sepals, petals, stamens, and pistils) were determined in several blackberry (Rubus subgenus Rubus Watson) cultivars (Boysen, Cherokee, Chester Thornless, Marion, and Thornless Evergreen) growing in one or more locations (Clarksville, Ark., Aurora and Hillsboro, Ore., and Kearneysville, W. Va.). Also, daily maximum, mean, and minimum temperatures were recorded at three sites (Clarksville, Aurora, and Kearneysville) for the September to April sampling period. In buds of `Boysen' and `Marion' from Oregon, sepal primordia were first observed in November and December, respectively. Further floral bud development continued into January. Sepal development in `Cherokee' buds occurred in October in Oregon and in December in Arkansas. At all three sites, the buds of `Chester Thornless' blackberry remained undifferentiated until spring. The average mean temperatures in Oregon were generally well above 5 °C during the bud sampling period, but were near 0 °C on most days from mid-December to January in Arkansas and from December to late-February in West Virginia. The phenology of flower bud differentiation varied among the cultivars and was strongly influenced by prevailing winter temperatures. The results suggest that the shortening day lengths of late summer trigger flower bud development in blackberry. Floral bud development in blackberry, once initiated, was continuous; however, periods of low temperature (<2 °C) can arrest development.
The effects of carbon dioxide enrichment on growth, photosynthesis, and postharvest characteristics of `Meijikatar' potted roses were determined. Plants were grown in 350, 700, or 1050 μl CO2/liter until they reached 50% flower bud coloration and then were placed into dark storage for 5 days at 4 or 16C. Plants grown in 700 or 1050 μl CO2/liter reached the harvest stage earlier and were taller at harvest than plants produced in 350 μl CO2/liter, but there were no differences in the number of flowers and flower buds per plant among CO2 treatments. Plants grown in early spring were taller and had more flowers and flower buds than plants grown in late winter. Shoot and root growth of plants grown in 700 or 1050 μl CO2/liter were higher than in plants produced in 350 μl CO2/liter, with plants grown in early spring showing greater increases than plants grown in late winter. Immediately after storage, plants grown in 350 μl CO2/liter and stored at 4C had the fewest etiolated shoots, while plants grown in 1050 μl CO2/liter and stored at 16C had the most. Five days after removal from storage, chlorophyll concentration of upper and lower leaves had been reduced by ≈50% from the day of harvest. Carbon dioxide enrichment had no effect on postharvest leaf chlorosis, but plants grown in early spring and stored at 16C had the most leaf chlorosis while plants grown in late winter and stored at 4C had the least leaf chlorosis.
Ethrel sprays were applied at 50 or 100 ppm at approximately 40%, 70% leaf fall (10/16/89 or 10/24/89, respectively) or at both times on `Redhaven' and `Allgold' peaches. Bud hardiness was determined biweekly by differential thermal analysis (DTA). Stage and percentage of bloom open during the bloom period were subjectively estimated.
Spraying trees with 100ppm Ethrel at 50% leaf fall significantly increased bud hardiness at mid-winter compared to other treatments. After a mid-winter freeze (-21.7 C on 12/21/89), there was no significant difference between % bud survival of any treatments. But, trees treated with 50 or 100ppm Ethrel had 10-20% better bud survival than other treatments. Buds of the 2 cultivars had statistically similar hardiness although DTA analysis indicated that Redhaven had a .5-.8 C lower freezing point than Allgold in mid winter. This trend was reversed close to bloom with Allgold having .7 C lower freezing point than Redhaven. The time of full bloom was significantly delayed by treating trees with 100ppm at 40% leaf fall or 50ppm at both 40 and 70% leaf fall the previous autumn.
Latent infection of Blackberry yellow-vein associated virus (BYVaV) in `Chickasaw' blackberry has been reported. However, plants with characteristic leaf symptoms, such as vein yellowing, chlorotic mottling, and oak-leaf patterns, have tested positive for BYVaV using reverse-transcription polymerase chain reaction. Experiments were initiated to determine if the symptoms expressed in BYVaV infected `Chickasaw' were caused by mixed virus infections. BYVaV, a recently identified crinivirus, was evaluated for synergistic interactions with Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV), and Raspberry bushy dwarf virus (RBDV). `Chickasaw' blackberry plants infected with BYVaV (single infection) were used as receptor plants to establish mixed virus infections with TRSV and ToRSV transmitted by nematodes and RBDV transmitted by bottle grafts. Characteristic symptoms of multi-virus infection will be presented and discussed.
We investigated the response of staminate and pistillate floral components of Prime-Jan™ and Prime-Jim™ primocane-fruiting blackberry (Rubus L. subgenus Rubus Watson) to three different growth chamber temperature regimes, 35.0/23.9 °C (HT), 29.4/18.3 °C (MT), and 23.9/12.8 °C (LT). Temperature was negatively related to flower size and morphological abnormalities in floral structures were evident in 41% and 98% of the MT- and HT-grown plants, respectively. The viability (stainability) of pollen from LT- and MT-grown Prime-Jan™ flowers exceeded 70%; that of Prime-Jim™ pollen was significantly reduced (<40%) by the MT regime. Pollen in-vitro germinability was negatively influenced by temperature but was unaffected by cultivar. LT-grown pollen held at 23.9 °C retained 63% of its original germinability over a 32-hour period; the germinability of LT-grown pollen held at 35.0 °C was decreased by 97% from its original level after 16 hours. Virtually all flowers cultured under HT conditions were male-sterile, exhibiting structural and/or sporogenous class abnormalities including petaloidy, malformation of tapetal cells, and microspores or failure of dehiscence. The duration of stigma receptivity, pistil density, and drupelet set were also negatively influenced by increasing temperature; values for these parameters of floral competency among control plants were reduced by 51%, 39%, and 76%, respectively, in flowers cultured under HT conditions. Herein, flowering and fruiting parameters and presumably the yield potential of Prime-Jan™ and Prime-Jim™ were adversely affected by increased temperature. However, assessment of their adaptative response to heat stress under field conditions awaits experimentation.
We investigated the responses of staminate and pistillate floral components of Prime-Jan and Prime-Jim primocane-fruiting blackberry (Rubus L. subgenus Rubus Watson) to three different growth chamber temperature regimens, 35.0/23.9 °C (HT), 29.4/18.3 °C (MT), and 23.9/12.8 °C (LT). Temperature was negatively related to flower size, and morphologically abnormal floral structures were evident in 41% and 98% of the MT- and HT-grown plants, respectively. Anthers of LT- and MT-grown plants dehisced. The viability of pollen (as deduced through staining) from Prime-Jan grown at LT or MT exceeded 70%, whereas that of Prime-Jim pollen was significantly reduced (<40%) by the MT regimen. In vitro pollen germinability (typically <50%) was negatively influenced by temperature but was unaffected by cultivar. Pollen useful life was diminished under HT conditions; LT-grown pollen held at 23.9 °C retained 63% of its original germinability over a 32-h period, while the germinability of that held at 35.0 °C for 16 hours decreased by 97%. Virtually all flowers cultured under HT conditions were male sterile, exhibiting structural or sporogenous class abnormalities including petaloidy and malformation of tapetal cells or microspores; HT anthers that were present, failed to dehisce. Stigma receptivity, pistil density, and drupelet set were also negatively influenced by increased temperature; values for these parameters of floral competency among control plants were reduced by 51%, 39%, and 76%, respectively, in flowers cultured under HT conditions. In this study, flowering and fruiting parameters, and presumably the yield potential of Prime-Jan and Prime-Jim, were adversely affected by increased temperature. However, their adaptive response to heat stress under field conditions awaits assessment.