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The genus Betula contains many important forest and ornamental species and a method of rapid clonal propagation of superior genotypes is needed. Thidiazuron (TDZ) is a potent synthetic plant growth regulator with cytokinin-like activity. TDZ was used to differentiate shoots after long term exposure to dichlorophenoxyacetic acid (2.4-D) as part of a larger study on clonal fidelity. Birch calli were cultured on Woody Plant Medium supplemented with 10-5 M 2,4-D for up to 30 weeks. The calli were transferred to media containing TDZ at concentrations of 10-6 to 10-9M. Most of the tissue which had not been exposed to 2.4-D differentiated shoots five weeks after being exposed to 10-6M TDZ. Increasing the of time exposure to 2.4-D or decreasing the concentration of TDZ delayed differentiation. Calli exposed to 2.4-D for more than 18 weeks rarely differentiated shoots regardless of the concentration of TDZ used.
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.
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.
Identical trials were conducted in a multibay high tunnel and an adjacent open field in southwestern Michigan to compare primocane-fruiting cultivars (Autumn Britten, Caroline, Chinook, Heritage) and floricane-fruiting cultivars (Canby, Encore, Heritage, Nova) of red raspberry (Rubus idaeus). Floricane-fruiting plots of ‘Heritage’ were pruned to produce fruit on floricanes and primocanes (double cropping). The most productive cultivars in both environments were ‘Nova’ and ‘Canby’ (floricane) and ‘Caroline’ and ‘Heritage’ (primocane). These cultivars produced annual yields of 5.5 kg·m−1 row in the tunnel and 2.5 kg·m−1 row in the field. The order of primocane harvest (earliest to latest) was the same in the tunnel and field: ‘Autumn Britten’, ‘Caroline’, ‘Chinook’, and ‘Heritage’. Cultivars with the greatest average berry weight in the tunnel and field were Encore and Nova (floricane) and Autumn Britten and Caroline (primocane). ‘Chinook’ and ‘Autumn Britten’ tended to have the highest incidence of gray mold (Botrytis cinerea) of primocane-fruiting cultivars, but incidence was similar in floricane cultivars. Overall mold incidence was 1% in the tunnel and 13% in the field. Leaf spot (Sphaerulina rubi), cane anthracnose (Elsinoe veneta), spur blight (Didymella applanata), and botrytis cane blight (B. cinerea) were common in the field but absent in tunnel. Phytonutritional analyses of primocane fruit indicated that genotype differences were not consistent across the two environments. Relative cultivar characteristics (harvest season, yield, berry quality) were similar in the field and tunnels, but the tunnel environment tended to increase plant vigor, yield, and fruit quality and suppress several diseases.
To investigate the variation in the phytonutrients of Cornelian cherry (Cornus mas L.), fruit was harvested at the blush (S1), red (S2), and ripe (S3) stages from five genotypes maintained at the Secrest Arboretum, Wooster, Ohio. The S1-S3 samples were characterized for color reflectance and then frozen at –28 °C. After storage, samples were analyzed for dry weight (DW), total soluble solids (TSS), sugars (FRU + GLU), organic acids (ORG), total phenols (PHE), total anthocyanins (ACY), individual anthocyanins (IA), hydroyzable tannins (HT), and antioxidant capacity (FRAP and ABTS). From S1 to S3, DW and TSS increased by 24% and 21%, respectively, and L, hue angle, and chroma values decreased. On a DW basis, all analytical parameters were significantly influenced by genotype and stage. The ACY levels rose 7-fold during ripening, but PHE contents declined by 10%. In ripe fruit, HT comprised the bulk of the PHE constituents, whereas ACY accounted for only 7.6% of PHE levels. Variability among genotypes was moderate for all ripe fruit parameters but ACY. Ripe fruit varied little in color parameters and ACY (fwb) and IA (fwb) were not significantly different among cultivars. The Cy 3-gal and pel 3-gal levels were negatively correlated. Antioxidant capacity declined 16% to 18% during ripening. Ripe fruit FRAP and ABTS values were higher than those reported for most fruits, averaging 596 ± 85 and 629 ± 85 μmol TE eq./gDW, respectively. ABTS and FRAP values were highly correlated with each other and with PHE and HT contents, but were loosely and negatively related to ACY levels. Considering our limited sample size, we concluded that the phytonutrient capacity of cornelian cherry is substantial, predominantly associated with tannins and moderately variable among genotypes.
To investigate phytonutrient accumulation in black raspberries, fruits of `Jewel' and `MacBlack' were harvested at stages from the onset of color development (S1) to ripe fruit (S7). S1–S7 samples were characterized for color reflectance and then frozen at –28 °C within an hour of harvest. Additional ripe fruit were maintained at 20 °C for 3 days to overripen (S8) before freezing. After storage, samples were analyzed for dry weight (DW), total soluble solids (TSS), fructose (FRU), glucose (GLU), and organic acid (ORG) contents; total phenolic (PHE) and anthocyanin (ACY) contents; individual cyanidin glycoside levels (ICG); and antioxidant capacity (FRAP and ABTS) by standard methodology. `Jewel' and `MacBlack' ripened similarly. Chroma values and DW percentage decreased while TSS levels, sugar contents (FRU+GLU), PHE, ACY, the ACY: PHE ratio, and ICG increased with progressive ripening stages (S1–S7). Values of PHE, ACY, and ICG were highly correlated (r < +0.95) with FRAP and ABTS values. ACY levels in S6 fruit were 18% to 23% less than those of S7; lower S6 ACY levels were associated with reduced antioxidant capacity in `MacBlack', but not `Jewel'. Overripened fruit (S8) exhibited increased DW (11% to 25%) and decreased sugar contents (16% to 17%), consistent with moisture and respiratory losses after harvest. After correction for these losses, S7 and S8 levels of PHE, ACY, FRAP, and ABTS were similar in `MacBlack'. However, as `Jewel' overripened, ACY levels and antioxidant activity increased 44% and 22% to 26%, respectively. Our data suggests that significant changes in the antioxidant behavior of black raspberries can occur during the periods surrounding peak ripeness.
This study was conducted to determine the effects of postharvest storage temperatures on the antioxidant capacity, anthocyanin compounds, phenolic constituents, and physico-chemical properties of black raspberries. Fresh `MacBlack' berries were stored at 4, 12, 20, and 28 °C for up to 11, 6, 4, and 3 days, respectively. Results showed that higher storage temperatures promoted tissue deterioration (cellular leakage), fungal growth, and moisture loss. The levels of the two major anthocyanins, cyanidin 3-rutinoside and cyanidin 3-xylosylrutinoside, increased by up to 2.7- and 1.9-fold, respectively, with increasing storage temperatures. The antioxidant capacity of berries, as measured by FRAP and ABTS assays, increased by up to 1.5- and 1.4-fold, respectively, which was accompanied by increases in soluble solids, total sugars, total phenolics, and total anthocyanin contents. Our findings indicate that postharvest storage at higher temperatures increases the level of bioactive compounds and antioxidant capacity in black raspberries, but this increase may be due in part to moisture loss and sugar metabolism. Storage at 4 °C maintained the level of bioactive compounds and antioxidant capacity present at harvest and prolonged the effective shelf life of the product. Further studies of black raspberry bioactive components as influenced by postharvest conditions and processing procedures (e.g., IQF, freeze-drying, air-drying) are warranted.