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  • Author or Editor: Michael G. Bausher x
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Growing transplants that can withstand the rigors of open-field production is imperative for the successful adoption of grafting in large-scale commercial fields and especially for those who seek to adopt this technology as an alternative to soil fumigation. This study examines the relationship of tensile strength to graft angle and plant survival. Tomato (Solanum lycopersicum) seedlings of ‘FL-47’ and ‘Rutgers’ were used as scions on ‘Roma’ rootstock under greenhouse and healing chamber conditions. Scions were grafted at angles of 20°, 45°, and 70°. After a period of 10 days, the plants were severed near ground level and subjected to pull force analysis. Pull force of the graft increased significantly with the increased graft angle. Pull force between the 20° vs. 70° angles increased significantly as well as those of 45° vs. 70° grafts (P ≤ 0.001). Increase in graft angle resulted in greater survival of grafted plants from 79% (20°), 81% (45°), and 92% (70°). Fifteen commercial rootstocks grafted at 70° had survival percentage rates between 97% and 100%. These studies demonstrate that the angle can significantly impact graft integrity and plant survival.

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Reciprocal grafts of two tomato (Solanum lycopersicum L.) cultivars were made by hand using commercial grafting techniques. The razor blade used to cut the rootstock or scion was first contaminated by making a single cut on tomato plants infected with either Tomato spotted wilt virus (TSWV) or Tomato mosaic virus (ToMV). Although no transmission of TSWV was observed in these experiments, ToMV was spread plant to plant through razor blade exposure to this virus. The presence of this virus was confirmed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) at 21 days post-inoculation. The highest rate of infection was 25% of the inoculated plants. The greatest number of positive virus assays was found in the first 10 plants of each experiment. These areas contained 84% of the DAS-ELISA-positive plants. Gaps of up to 10 plants occurred during serial inoculation before infection resumed. Random dispersion occurred in two experiments. Similar results were observed whether the contaminated implement was used to cut the rootstock or the scion before graft assembly. This work demonstrates that some viruses from a single contamination can be moved in a serial manner during the grafting process, especially with varieties with minimal or no resistance to viral plant pathogens. Also, visual diagnosis cannot always be relied on as a means of eliminating virus-infected plants, especially when higher greenhouse and annealing temperatures are maintained.

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Vegetative grafting has been proposed as a technique for managing diseases in tomatoes under open-field conditions. Over 2 successive years, we investigated the use of grafting under open-field fresh tomato production and found a serious limitation with current grafting techniques, which resulted in recurring rootstock shoot regrowth (“suckering”) from the rootstock cotyledons when left intact. Left unchecked, the regrowth of tomato rootstocks can envelop the experimental scions, which can impact the growth of field-grown tomatoes. In the Fall of 2007, the cultivars Multifort, Aloha, and TX-301 with ‘FL-47’ scions were grafted by a commercial propagator. These grafted plants were planted in a field experiment and after a time period, the number of rootstock suckers was counted and removed. This process was repeated over five time periods. In 2008, we grafted all of the plants below the rootstock cotyledons. During five different time periods spanning 57 d, bud regrowth from the rootstock occurred in all studied rootstocks in 2007. The difference in the 2 years was dramatic. In the first year, the number of plants with rootstock regrowth was as high as 84.6% in some of the plots for ‘Multifort’, 30.7% for ‘Aloha’, and 15.4% for ‘TX-301’. In the second year, with a different grafting technique, no regrowth from the rootstocks was observed. Even when the rootstock regrowth was removed in 2007, the rootstock sprout growth would reappear from the rootstock. The statistical interaction of the percentage of plants with rootstock regrowth for all recorded dates in 2007 was significant for ‘Multifort’ (Tukey-Fischer P ≤ 0.05) but not ‘Aloha’ or ‘TX-301’. Although the study also contained fumigation treatments, no interaction of soil treatments on root sprouting was observed. Since adopting this method, rootstock regrowth has not been observed in subsequent field experiments for the past 3 years.

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Abstract

Polyclonal antibodies against the major soluble glycoprotein of trifoliate orange [Poncirus trìfoliata (L.) Raf.] were produced in rabbits. The antisera were used to detect the glycoprotein in foliar protein extracts from a hybrid of Poncirus and Citrus genotypes by immunoblotting. One of the sera was found to be highly specific and was suited to indicate trifoliate gene expression. Cross-reacting bands in protein extracts from citrus callus tissue and in the medium of suspension cell cultures suggest that tissue culture systems can be used for biochemical studies of glycoproteins, but not for genotype characterization.

Open Access

Abstract

Chemical thinning of peaches was conducted under orchard conditions using CPA, followed by standard hand thinning, on the cultivars ‘Jerseyqueen,’ ‘Sunhigh,’ ‘Redhaven’, ‘Sunqueen’ and ‘Rio Oso Gem.‘ Timing of the 3 sprays at 150 ppm was based on the water volume displacement of 100 fruits selected at random from each plot: a) at 200 ml displacement, b) at 280 ml, and c) at 280 ml plus 4 days. The control was hand thinned only. Ovule length was measured at each spray timing and found to be 7–10 mm at the 280 ml water displacement; both ovule length and water displacement techniques were used to time CPA sprays in over 2000 acres of New Jersey orchards in 1968.

Timing of the CPA thinner for optimum effectiveness in this experiment varied with cultivar. Individual fruit weight was greater on CPA-thinned trees than on the controls for the cultivars ‘Redhaven,’ ‘Rio Oso Gem,’ ‘Sunqueen’ and ‘Sunhigh’ at harvest. Chemically thinned ‘Jerseyqueen’ did not show an increased mean fruit weight at harvest. Yield reductions occurred on ‘Sunhigh’ at the 280 ml timing and on ‘Redhaven’ at the 280 ml + 4 days timing, due apparently to subsequent over-thinning by hand. Shading increased the thinning effectiveness of CPA on all cultivars. ‘Jerseyqueen’ and ‘Redhaven’ were difficult to thin with CPA under the conditions of this experiment. ‘Rio Oso Gem’ was moderately difficult, while ‘Sunhigh’ and ‘Sunqueen’ were thinned readily.

Open Access

Abstract

‘Valencia’ oranges (Citrus sinensis (L.) Osbeck) damaged with rust mite (Phyllocoptruta oleivora Ashmead) responded to the abscission-accelerating chemical glyoxal dioxime (ethanedial dioxime) with greater ethylene production and greater reduction in bonding force than undamaged fruit. More than 90% of the 14C-glyoxal dioxime taken up by the rind was absorbed during the first 24 hrs. Absorption of 14C-glyoxal dioxime by rind tissue of mite-damaged fruit was more rapid than that of undamaged fruit. The differences in uptake of 14C-glyoxal dioxime due to mite damage were greatest on the first day after treatment, which was also the time of maximum ethylene production in response to glyoxal dioxime. The increased uptake in mite-damaged fruit is partially responsible for the increased effectiveness of glyoxal dioxime. It is likely that mite-damaged fruit are more permeable to many agricultural chemicals than undamaged fruit.

Open Access

Abstract

Ethylene production in peel explants of ‘Valencia’ oranges [Citrus sinensis (L.) Osbeck] treated with 5-chloro-3-methyl-4-nitro-1H-pyrazole (Release) was similar in pattern to ethylene production by whole fruits treated with the chemical. Smaller amounts of ethylene were produced by untreated peel explants. Explants from fruit harvested in October and March showed similar patterns of ethylene evolution when untreated and when Release was applied. The response to this chemical was localized in the flavedo. Ethylene production was dependent on temperature in both untreated and Release-treated peel explants, but the ethylene response to the chemical was particularly temperature-dependent. The temperature optimum in both cases was approximately 25°C. Peel disks from regreening fruit generally produced less ethylene than disks from nongreening fruit when Release or glyoxal dioxime (ethanedial dioxime, Pik-Off) was applied. The magnitude of the difference between regreening and nonregreening disks depended on the concentrations of Pik-Off or Release applied.

Open Access

Abstract

The effect of wounding and abscission-accelerating compounds on ethylene production in ‘Valencia’ orange (Citrus sinesis (L.) Osb.) was studied using enclosed peel explants. Three peel disks, 10 mm in diameter, produced a maximum of about 5.5 nl hour ethylene during the second day after excision from the fruit. Higher rates of ethylene production were observed in albedo than in flavedo tissue from 30 to 72 hours after excision. Treatment with the abscission accelerant 5-chloro-3-methyl-4-nitro-l H-pyrazole (Release) more than doubled ethylene production, an effect which was prevented by cordycepin. Inhibition of ethylene production by rhizobitoxine and cycloheximide indicated that ethylene production induced by either physical or chemical wounding in citrus peel proceeds from methionine and has requirements similar to those of other tissues.

Open Access

Abstract

Temperature effects on glyoxal dioxime (Pik-Off) stimulation of ethylene production and fruit loosening and on uptake of 14C-glyoxal dioxime were investigated using ‘Hamlin’ oranges [Citrus sinensis (L.) Osb.] harvested with petioles attached. Oranges treated with 250 ppm glyoxal dioxime produced significantly more ethylene than untreated fruit at 20, 25, and 30°C but not at 10 or 15°. Fruit loosening was correlated with internal ethylene concentration, producing a significant loosening effect for glyoxal dioxime at 20, 25, and 30°. Lack of effectiveness of glyoxal dioxime for inducing fruit loosening at low temperatures (10 and 15°) cannot be explained by a reduced rate of uptake but may result from impairment of ethylene biogenesis by fruit tissue.

Open Access

Fresh pollen from Citrus tachibana Macf. was oven-dried (37C), freeze-dried, or placed into anhydrous acetone, and stored at -20C over silica gel. Pollen freeze-dried or stored in anhydrous acetone did not germinate 24 hours after treatment; oven-dried pollen germinated in 1 hour and was comparable to fresh pollen. Pollen that was oven-dried for 12 hours and stored for 1 year was used to pollinate a monoembryonic hybrid of `Temple' (origin unknown) × `Orlando' (C. paradisi Macf. `Duncan' ×C. reticulata Blanco `Dancy'). Glutamate-oxaloacetate transaminase (GOT) isozyme profiles verified progeny hybridity.

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