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The experiment compared productivity and vegetative growth of the Hass avocado on three avocado root rot resistant rootstocks and one susceptible rootstock. Hass trees on Duke 7 reported the largest number of fruit per tree and on G 755c the smallest five years after planting. Trees on Topa Topa and Duke 7 reported the highest average production four years after planting. Trees on G 755c were significantly lower in the amount of leaf N. Trees on Toro Canyon and G 755c showed significantly lower amounts of Na. Trees on Duke 7 showed a significantly higher level of Mn. Trees on G 755c were significantly smaller two years after planting. Trees on Topa Topa and Duke 7 showed a significantly larger canopy diameter than those on G 755c four years after planting. Trees on G 755c showed the smallest mean shoot growth four years after planting. Trees on G 755c had significantly larger trunk circumferences three and four years after planting. No statistical differences were found among rootstocks as to freeze damage to the Hass scions.
Heat stress can limit yield in pepper (Capsicum spp.), generally through flower and fruit abortion. A kaolin-based particle film, originally developed to protect fruit trees from insects, has been found to reduce temperatures in tissues of plants. A kaolin-based particle film was tested to determine if it could be used to improve yields of pepper in Oklahoma and Georgia. In Oklahoma, seedlings of a bell pepper, `Jupiter', and a nonpungent jalapeño, `Pace 103', were transplanted at three progressively warmer planting dates from mid-May to mid-July 2002 and 2003, that would ensure that inflorescences would be subject to high day and night temperatures and treated with the kaolin-based particle film. Applications were begun as the first flowers were set and continued through the settings of the first three flushes of flowers on a three-times a week schedule, or on an as needed basis, to determine if the kaolin-based particle film improved yield. In Georgia, the bell peppers `Camelot' and `Heritage VR' were transplanted on 24 Apr. 2003, and treated with the kaolin-based particle film. In addition to yield, physiological measurements and disease incidences were recorded in Georgia. In both locations treatment with water only served as controls. In Georgia, the kaolin-based particle film had no significant effect on net photosynthesis, stomatal conductance, leaf transpiration or leaf temperature, as measured at midday on clear days. In Oklahoma, planting bell pepper after 15 May is not recommended. Planting the nonpungent jalapeño after mid-June can reduce yields. The kaolin-based particle film did not affect yield at either location and is not recommended for use on peppers.
The appearance of blossom-end rot (BER) in tomato is related to a decrease in the absorption and translocation of Ca due to excessive salinity in the soil solution. An experiment was conducted to investigate the effects of calcium nitrate (NT), EDTA-Ca (ED) and Aminoquelant-Ca (AQ)—a product containing Ca, B and protein hydrolisate—on the yield and incidence of BER when applied to the leaves of tomato (Lycopersicon esculentum Mill. `Durinta') grown in the open with a drip irrigation using saline water from a well (mean ECw 5.2 dS·m–1). The three calcium treatments and control were replicated four times, with 12 plants per replication, in a completely randomized design. Although yield per plant was higher with AQ, the difference was not statistically significant. Fewer fruit were affected by BER after treatment with ED and AQ than with NT and in the control. Leaf Ca concentration did not differ significantly between treatments. However, leaf B concentration was higher after treatment with AQ. Fruit Ca and B concentrations did not differ significantly in any treatment. The total free amino acids content in leaves was higher after AQ treatment than in the other treatments and control, although no significant difference was observed between the treatments in the fruit.
This work was conducted for evaluate the influence of clear and black polyethylene mulches, used alone or combined with floating rowcover (FRC) and plastic perforated microtunnels, on insect populations, growth and yield of muskmelon. Treatments evaluated were 1) clear plastic + FRC, 2) polyethylene perforated microtunnel, 3) clear plastic + polyethylene not perforated microtunnel, 4) black plastic + FRC, 5) clear plastic, 6) black polyethylene, 7) clear plastic + oil, and 8) bare soil. Aphids and sweetpotato whitefly adults and nymphs were completely excluded by floating rowcovers while the plots covered. The export and national quality fruit yield was major in the mulched beds in relation to control. Clear polyethylene mulch + FRC increased number of fruit and export marketable fruit of cantaloupe (45.2% and 44.8%) with respect to black plastic + FRC, respectively. It is proposed that, under tropical conditions and under high insect stress, mulches combined with floating rowcovers should be selected for their effects on insects in addition to their effects on melon yield. Polyethylene microtunnels were found not economical for cantaloupe production in western Mexico.
Apricot (Prunus armeniaca L. cv.'Helena') shoots grown on a proliferation medium containing 3% sucrose, 0.4 mg·L–1 benzyladenine (BA), and 0.04 mg·L–1 indolebutyric acid (IBA) and solidified with 0.6% agar were stored at three different temperatures in the dark for up to 24 weeks. All shoots remained viable for 24 weeks when stored at 3 °C, while at 14 °C the percentage of survival decreased quickly after 12 weeks of storage. At 7 °C, percentage of survival started to decline after 18 weeks of storage. Shoots stored at 3 °C had the highest regeneration rates and shoot lengths following transfer to standard proliferation conditions. This temperature also had a beneficial effect on shoot proliferation during the first 12 to 18 weeks of the experiment.
Greenhouse rose (Rosa × spp. L.) production is facing the use of poor-quality irrigation waters and regulatory pressures to recycle runoff and drainage effluents. Two experiments (were conducted to evaluate the yield and quality and ion accumulation responses of roses grafted on various rootstocks to increasing salinity stress. In Expt. 1, the scion ‘Bridal White’ grafted on ‘Manetti’, R. odorata (Andr.), ‘Natal Briar’, and ‘Dr. Huey’ were irrigated over four flowering cycles with complete nutrient solutions supplemented with NaCl at 0, 5, and 30 mm. In Expt. 2, plants of ‘Red France’ on ‘Manetti’ and ‘Natal Briar’ were irrigated over six flowering cycles with complete nutrient solutions supplemented with NaCl + CaCl2 (2:1 m ratio) at 0, 1.5, 3, 6, 12, and 24 mm. Salt concentration increases significantly and negatively affected the biomass, cut flower production, and foliage quality of the roses in both experiments, but the responses were modulated by rootstock selection. ‘Manetti’ plants in general sustained better absolute and relative biomass and flower yields, accumulated less Na+ and Cl− in its tissues, and showed less toxicity symptoms with increasing salinity than the others. ‘Natal Briar’ also had similar absolute productivity responses as ‘Manetti’ but were afflicted by a significantly different mineral nutrient profile, including higher accumulations and toxicities with Na+ and Cl− that led to lower foliage visual ratings. Conversely, the relative yields of plants on ‘Dr. Huey’ and R. odorata were similarly reduced by increasing salinity, but the former had lower Na+ and Cl− concentrations in its tissues and better visual scores than the latter, which fared as the worst. A combined analysis of the results suggests that on a productivity basis (biomass and flower yields), greenhouse roses could withstand overall maximum electrical conductivities (i.e., osmotic effects) of applied fertigation solutions of 3.0 ± 0.5 dS·m−1. On the other hand, and considering the aesthetic responses (visual scores) of on-plant and harvested foliage (cut flower shoots), greenhouse rose tolerance to applied Na+ and Cl− concentrations (ion-specific effects) could range up to 10 ± 2 mm.
Abstract
Ethylene treatment affected protease activity in ovaries, but not petals, of cut roses (Rosa hybrida L.) ‘Sonia’. Protease activity in ovaries of ethylene-treated flowers decreased within the first 3 days and then remained at the same level until the 12th day. In ovaries from controls, protease activity decreased from day 6 until day 9 and then remained constant until day 12. Protease activity of petals did not differ significantly between the ethylene-treated and control flowers; it was constant until day 6 and then increased steadily until day 12. Differences between ethylene-treated and control flowers were visible immediately after treatment (day 1) and until day 3, as the sepals of the ethylene-treated flowers reflexed. Later (day 6), this difference disappeared as the sepals of the control flowers also reflexed. On day 9 the outer petals of the ethylene-treated flowers were bluish, whereas the controls were not. There were no other differences in development between treated and control flowers.
Several studies were undertaken in commercial nonirrigated `Hass' avocado orchards under the subhumid semiwarm subtropical climate of the state of Nayarit, Mexico, with the following objectives: 1) to determine the frequency and intensity of vegetative shoot flushes and their contribution to the production of floral shoots, 2) to quantify the effect of tree fruit load on the occurrence of vegetative shoot flushes during the year and the relationship between vegetative and reproductive shoot number during flowering, and 3) to determine the time when apical buds borne on the major vegetative shoot flushes reached irreversible commitment to flowering (floral determination) through the use of shoot defoliation and girdling. Data trees were selected in two orchards based on their current crop load. Four to five branches per tree were tagged, and the number and intensity of vegetative flushes that developed during 2 years, as well as the type of growth produced by apical buds of shoots of different ages, were recorded at the end of the winter bloom periods for two separate years, 1999 and 2001. In a separate experiment using a different set of trees, winter and summer flush shoots were defoliated (year 1) or defoliated and girdled (year 2) at different stages of bud development from September to January in each case. Four vegetative flushes occurred each year. The winter flush that emerged in Feb. 1998 made the greatest contribution to the 1999 winter bloom—76.5% of the shoots produced floral shoots. Contributions of the summer 1 (late July 1998), summer 2 (early Aug. 1998), and summer 3 (late Aug. 1998) flushes to flowering were intermediate. A total of 30.6%, 36.4%, and 19% of the shoots produced floral shoots respectively. All four vegetative flushes produced a similar number of vegetative shoots during winter bloom. Evaluation of the 2001 winter bloom for trees with high (>95 kg fruit/tree) and low (<70 kg fruit/tree) crops showed no effect of tree fruit load on the production of vegetative or floral shoots by winter or summer vegetative flushes. Irrespective of time of treatment (shoot defoliation and girdling) or shoot age, irreversible commitment to flowering of apical buds occurred by 15 Oct., and this stage was associated with an average of 27.5 chilling days (temperature, ≤19 °C) for both years. Buds irreversibly committed to flowering were closed and pointed, with partial senescence of bud scales. Anatomically, the buds showed a convex primary axis meristem and four secondary axis floral shoot meristems.
Colored shade nets may affect plant growth and fruit yield of horticultural crops. The understanding of how colored shade nets influence plants, however, is far from complete. The objective of this study was to determine the effects of colored shade nets on bell pepper fruit yield, postharvest transpiration, color, chemical composition, and antioxidant capacity. The experiment was conducted in Tifton, GA, during the spring of 2015 and 2016. The experimental design was a randomized complete block with four replications and five colored shade net treatments (black, red, silver, and white nets, and an unshaded control). The nets were placed on the top of wooden rectangular structures (15 m wide × 6 m long × 5 m high), leaving the sides of the structures uncovered. Results showed that in both 2015 and 2016, marketable and total fruit number, yield, and individual fruit weight were reduced under the unshaded treatment. There were inconsistent differences in marketable and total fruit number, yield, and individual fruit weight among colored shade nets. Postharvest fruit transpiration and skin permeance were also reduced in unshaded conditions, and no differences were found among colored shade nets. Fruit color L* and b* values were highest, and a* value was lowest in unshaded conditions. Fruit soluble solids, total phenols, flavonoids, and antioxidant capacity [Cupric Reducing Antioxidant Capacity (CUPRAC) and Trolox Equivalent Antioxidant Capacity (TEAC)] responded differently among colored shade nets in the 2 years. Total phenols, flavonoids, and TEAC, however, were among the highest in unshaded conditions. In conclusion, results of the present study support previous findings that shade nets increase fruit yield and quality in bell pepper compared with fruit produced in unshaded conditions. Nevertheless, there were no consistent differences in fruit total and marketable yield and postharvest fruit transpiration and chemical composition of fruit produced under colored shade nets.