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- Author or Editor: Joseph C. Scheerens x
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Peroxidase activity in extracts from freeze-dried tissue of Fragaria × ananassa Duch. cv. Chandler was highest in tissue-cultured (TC) plants, followed by field-grown (FG) and lowest in greenhouse (GH) plants. Among tissue types, activity was highest in petioles, with leaves second highest. Fruit, root, and crown tissue all exhibited low or no activity. When subjected to isoelectric focusing (IEF), petiole tissue extracts exhibited more isozymes than extracts from other organs regardless of staining substrate. Using 4-chloro-1-naphthol and H2O2 as substrates, anionic and cationic isozymes were observed in TC petiole extract with nine isozyme bands ranging in pI from 3.9 to 9.5. In TC leaf extract an isozyme at pI 7.4 was observed that was not present in other organ extracts when H2O2 and benzidine, p-phenylenediamine or 3-amino-9-ethylcarbazole were used as substrates. Specific isozymes and number of isozymes varied according to plant organ and developmental stage. Mature leaves and over-ripe fruit appeared to exhibit more activity and a larger number of isozymes than developing tissues of those plant organs.
The genus Aesculus (buckeyes and/or horsechestnuts) is composed of 13 species and a number of interspecific hybrids. Pollen from 11 genotypes from five Aesculus species and the hybrid Aesculus ×carnea were used to develop an in-vitro germination test to evaluate pollen viability under various storage treatments. This test was optimized using samples of both fresh pollen and pollen that had been stored up to 1 year. The most effective medium contained 20% sucrose, 100 mg·L-1 H2BO3, 150 mg·L-1 Ca(NO3)2, and 1% agar. The highest germination percentage was observed at 15 °C across all storage treatments. Fresh pollen germinated in excess of 80% over a wide range of germination temperatures. Based on this, all specimens studied would be good pollen parents. The differences in pollen germination between storage at -20 and -80 °C were nonsignificant, but the duration of the storage period was highly significant. At 3 months, viability remained above 60% for four of the six species/hybrid tested. However, at 12 months, all pollen tested dropped below the threshold for good fruit set based on in-vitro pollen germination. Based on these observations, short-term pollen storage may permit crosses between parents with temporally separate flowering phenologies. However, conventional storage procedures are inadequate to maintain pollen collected from a male parent for crosses in subsequent growing seasons.
Leaf disk bioassays based on oviposition and damage accrued during 72 hours were used to screen 76 strawberry (Fragaria spp.) cultivars for resistance to the twospotted spider mite (Tetranychus urticae Koch). Oviposition rates (eggs/female per day) and damage scores were both highly variable, allowing cultivars to be classified, according to a combination of these two variables, into six categories of susceptibility or resistance: highly susceptible- `Canoga', `Ozark Beauty', `Scott', and `Tangi'; resistant—'Aiko', `Annapolis', `Apollo', `Bounty', `Cardinal', `Douglas', `Dover', `Fairfax', `Fern', `Floridabelle', `Glooscap', `Governor Simcoe', `Hecker', `Kent', `Pajaro', `Parker', `Rainier', `Redcoat', and `Vesper'; and highly resistant—`Profumata di Tortona' (F. moschata Duch.). Bioassay based on oviposition rates and damage scores was considered to be an efficient method to eliminate susceptible accessions from a breeding program, but authentication of putative resistance may require further testing in vivo.
As a prelude to interspecific hybridization, we compared the floral biology of bottlebrush buckeye (Aesculus parviflora) and red buckeye (A. pavia) by examining inflorescence morphology, pattern of floral anthesis, sex expression, and the effects of panicle decapitation on complete flower development. Inflorescences of both species (n = 1606) were randomly selected and analyzed for length, total number of flowers and complete flower number and location. The pattern of anthesis was observed in four genotypes using 10–30 inflorescences per plant. For each flower, its date of anthesis, position on both the rachis and cincinnus, and sex were recorded. For studies of panicle decapitation, sets of panicles were selected and one member was severed in half early in development in an attempt to increase the number of complete flowers. More than one-fourth of all panicles observed were completely staminate. For both species, the ratio of complete flowers to male flowers (C:M) within mixed panicles was about 5%. Complete flowers were observed in the basal portion of A. pavia inflorescences and in the apical portion of A. parviflora inflorescences. Anthesis progressed from base to tip over a period of 6–11 days. Complete flowers are present in A. pavia from the beginning of anthesis but do not appear in A. parviflora until the fifth day of anthesis. Staminate flowers are present throughout anthesis in both species. Severing panicles in half increased the potential for differentiating complete flowers. In conclusion, the frequency of complete flowers in both species was quite low, but could be increased by panicle decapitation to increase opportunities for controlled hybridization.
The commercial and ornamental potential of three apple-berry polyculture systems was ascertained by monitoring the above-ground performance of component species in plots of `GoldRush' apple (Malus ×domestica Borkh.) trees on M.7 rootstock cropped with either blackberry (Rubus spp. L. `Navaho'), edible honeysuckle (Lonicera caerulea L. `Blue Belle' and `Blue Velvet'), or jostaberry (Ribes nidigrolaria Bauer `Josta') as understory plants. Polyculture plots and corresponding monoculture controls were established in 1999, with berry plants at recommended (R) or close [(C), half-recommended] spacings. Blackberries and jostaberries planted in monoculture at recommended spacings [i.e., control (R) plots] amassed dry weights >1 kg/plant by Fall 2001; the dry weight of edible honeysuckle from comparable plots was slightly >0.3 kg/plant. In 2001, blackberry yield (3.1 kg/plant) and fruit weight (3.4 g) were typical of `Navaho' plantings of similar age, whereas jostaberry was only moderately productive (yield = 286 g/plant; fruit weight = 1.4 g). Edible honeysuckle productivity (yield = 13 g/plant, fruit weight = 0.5 g) was minimal, due to disparate flowering phenology between cultivars. `GoldRush' apple growth and productivity (yield = 25 kg/tree; fruit weight = 158 g) was consistent with values expected for trees of similar age. Blackberry plant dry weights were reduced by 20% to 33% when planted at close spacing, whereas blackberry yields were reduced 35% to 38% when grown in polyculture with apple. Both polyculture and plant spacing significantly reduced jostaberry dry weights (i.e., 12% and 24%, respectively) relative to the control, but neither significantly affected jostaberry yield. Conversely, both close-spaced planting and the presence of an apple tree improved the yield of edible honeysuckle. Apple performance was not affected by the presence of an edible honeysuckle understory, but apple growth factors were reduced in blackberry and jostaberry polycultures by as much as 65%. Apple bloom, fruit set, and yield were also significantly reduced in apple-blackberry and apple-jostaberry plots, with fruit numbers/tree averaging <5 in all except the apple-blackberry (C) treatment. None of the polyculture treatments studied were suitable for profitable fruit production. However, each of the polyculture constituents exhibited unique, beneficial attributes with respect to their use as components within an edible landscape.
Six strawberry cultivars (`Earliglow', `Honeoye', `Idea', `Jewel', `Northeaster', and `Seneca') were grown organically on three different composts (yard waste, dairy barn waste, and vermicompost). Organic treatments were contrasted against a synthetic fertilizer standard, a conventional pesticide standard and an untreated control. Plots were rated for tarnished plant bug (Lygus lineolaris) damage during the growing season. At harvest, berries were examined for their ascorbic acid levels and total anthocyanin and phenolic contents. Ascorbic acid content of berries in different cultivars and treatments were similar. As expected, fruit anthocyanin and phenolic contents were significantly different among the cultivars, and ranged between 160–230 μg·gfw-1 and 1039–1333 μg·gfw-1, respectively. Among treatments, anthocyanin contents of strawberries were not significantly different, but berries grown on the conventional pesticide standard had 8% to 12% lower total phenolic content than the other treatments. In organic treatments, production of phenolic compounds may have been induced in response to increased tarnished plant bug feeding. This putative biotic stress defense mechanism was seen most dramatically on tarnished plant bugsusceptible cultivars. However, as differences in phenolic levels were greater among cultivars than among treatments, cultivar choice may be a more important consideration than growing system for optimizing antioxidant levels in commercially available fruit.
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.
In addition to their physiological and metabolic roles, anthocyanin (Antho) levels in lettuce contribute to visual and nutritional value-based assessments of crop quality. Although 7 genes are now thought to help regulate Antho synthesis, deposition and/or degradation in lettuce, the genetic and abiotic controls of Antho levels remain less well characterized in lettuce than other plants. Previous greenhouse studies demonstrated that Antho levels in diverse lettuce varieties are a function of temperature and lighting regimen. Here, three strongly related Lolla Rossa-type varieties (`Lotto', `Valeria', and `Impuls') varying in the number of genes controlling intensity of anthocyanins were subjected to differential temperature conditions in growth chambers to better discern the independent and interactive effects of temperature (T) and variety (V) on Antho levels. Fifteen day-old seedlings were placed into one of three chambers maintained at 20 °C day/night (D/N), 30 °C/20 °C D/N or 30 °C D/N. Antho levels were measured in leaf tissue collected 30 d after transplanting. The entire experiment was replicated twice. Although significant, the T x V interaction resulted from differences in the magnitude, not direction, of the change in Antho concentrations among varieties with changes in T. This suggests that T was a main driver of Antho levels in this study. Regardless of V, Antho concentrations were highest, moderate and lowest after growth at 20 °C D/N, 30 °C/20 °C D/N and 30 °C D/N, respectively. Likewise, regardless of T, Antho levels followed the pattern `Impuls' (three genes) > `Valeria' (two genes) > `Lotto' (one gene). Correlations among instrumented and human eye-based evaluations of color are also being tested in samples from both studies.