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Abstract

Two hundred eight-four Lycopersicon spp. genotypes reported to have some resistance to bacterial pathogens of tomato (L. esculentum Mill.) were inoculated in the field with Xanthomonas campestris pv. vesicatoria (XCV), the incitant of bacterial spot, and rated for disease severity in summer 1982 and/or summer 1983. One line tested in 1983, Hawaii 7998, had no definite XCV lesions and later was determined to be resistant to XCV in the laboratory. Genotypes with the highest levels of resistance during 2 years of testing were: Ohio 4013-3, Ohio 4014-4, Heinz 1568-F3, [(Subarctic Delite × MH1) × H603] F5, L556, ‘Campbell-28’, PI 127813, Heinz 603-F11, PI 224573, ‘Monense’, ‘Heinz 2990’, and PI 324708. Genotypes with highest levels of resistance in one year of testing were PI 379032 and ‘Burgess Crack Proof. In 1982, PI 270248- ‘Sugar’ had a high level of resistance to XCV on fruit, but foliage was susceptible.

Open Access

A `spray-inoculation seedling screening procedure was developed for detecting resistance to Xanthomonas campestris pv. vesicatoria (Doidge) Dye, causal agent of bacterial spot of tomato (Lycopersicon esculentum Mill.). Two-week-old transplants were preconditioned under 95% humidity for 16 hours before spray inoculation and then rated for bacterial spot 2 weeks later. Resistant plants could also be distinguished from susceptible genotypes using a modified bacterial speck [Pseudomonas syringae pv. tomato (Okabe) Young, Dye, and Wilkie] screening procedure (cotyledon-dip technique). When results of both screening methods were compared to field ratings from three previous seasons, significant correlations were more frequently observed for the spray-inoculation method. In Summer 1991, individual plants were evaluated by the spray-inoculation technique and then were placed in the field to determine susceptibility under field conditions. Correlations (r = 0.28 to 0.34) between spray-inoculation seedling screening ratings and field ratings, although low, were significant (P ≤ 0.0001). More than 90% of susceptible plants could be eliminated, saving labor, space, and time.

Free access

Abstract

Soils, and leaf and fruit tissues were collected from 200 peach orchard sites during the 1970 growing season. Results obtained were not markedly different from those obtained in an earlier survey in 1962. Most of the soils were quite acid and the peach leaf N levels were below optimum. Most growers appeared to be overfertilizing with P but applying adequate K. Peach fruit were quite high in K, accounting for a sizeable removal of K from the soil.

Open Access

Abstract

Tomato (Lycopersicon esculentum Mill.) accession PI 270248 (‘Sugar’) had high levels of resistance to bacterial spot [incited by Xanthomonas campestris pv. vesicatoria (Doidge) Dye] on fruit, but foliage was susceptible. Hawaii 7998 (H7998) was highly resistant to foliar infection, but was intermediate in resistance to fruit infection. Fruit spot on hybrids between ‘Sugar’ and H7998 was usually intermediate to the parents. Occasionally, disease incidence of hybrids was not statistically different from one or both parents, but tended to resemble ‘Sugar’ more closely than H7998. There were no significant differences between reciprocal hybrids, indicating a lack of cytoplasmic inheritance. Under low disease incidence, hybrids between ‘Sugar’ and ‘Walter’ (susceptible to bacterial spot on fruit and foliage) had fruit spot incidence similar to ‘Sugar’ and significantly less than ‘Walter’. Thus, there was a high level of dominance for resistance to bacterial spot on fruit.

Open Access

Abstract

Weekly foliar fertilizer applications of 10 ppm NO3-N [as Ca(NO3)2] or NH4-N [as (NH4)2SO4] significantly reduced dry matter, N accumulation, and yield of ‘Blue Lake 274’ snap bean (Phaseolus vulgaris L.) grown in solution culture. The reduction in dry matter and N accumulation were greatest with the NH4-N vs. the NO3-N foliar treatment. Data obtained in this study indicates that the cultural practice of applying NH4 or NO3 fertilizer through an overhead irrigation system may reduce snap bean yield.

Open Access

Bacteriophages specific to Xanthomonas campestris pv. pelargonii (Xcp), the causal agent of bacterial blight of geranium, Pelargonium ×hortorum L.H. Bailey, were isolated from soil and sludge samples from Florida, California, Minnesota, and Utah. Sixteen phages were evaluated for their potential to lyse 21 Xcp strains collected from around the world. The Xcp strains varied in their susceptibility to the phage isolates with 4 to 14 phages producing a lytic or highly virulent reaction. A mixture of five h-mutants was developed from phages that exhibited the broadest host-ranges and tested against the same Xcp strains. The h-mutant phage mixture lysed all 21 Xcp strains. Three experiments were designed to determine the efficacy of using a mixture of four h-mutant phages to control the spread of the bacterial blight pathogen on potted and seedling geraniums under greenhouse conditions. Plants surrounding diseased inoculated plants were treated with a phage mixture at 5 × 108 pfu/mL daily, biweekly, or triweekly, or treated with Phyton-27®, at 2.0 mL·L-1 every 10 or 14 days. In potted geraniums, daily foliar sprays of the phage mixture had reduced disease incidence and severity by 50% and 75%, respectively, relative to control plants after 6 weeks. In two plug experiments, the phage mixture applied daily also had reduced disease incidence and severity by 69% and 86%, and 85% and 92%, respectively, when compared with controls after 5 weeks. In all three experiments, disease incidence and severity were less for plants treated daily with phages than for those treated less frequently with phages or with Phyton-27®. Chemical name used: copper sulfate pentahydrate (Phyton-27®).

Free access

A mixture of host-range mutant (h-mutant) bacteriophages specific for tomato race 1 (T1) and race 3 (T3) of the bacterial spot pathogen, Xanthomonas campestris pv. vesicatoria (Doidge) Dye was evaluated for biological control of bacterial spot on `Sunbeam' tomato (Lycopersicon esculentum Mill.) transplants and field-grown plants for two seasons (Fall 1997 and Fall 1998). Foliar applications of bacteriophages were compared with similar applications of water (control) and of copper/mancozeb bactericides, the commonly used chemical control strategy for tomato seedling and field production. In 1997, the incidence of bacterial spot on greenhouse-grown seedlings was reduced from 40.5% (control) to 5.5% or 0.9% for bactericide- or bacteriophage-treated plants, respectively. In 1998, the incidence of bacterial spot was 17.4% on control plants vs. 5.5% and 2.7% for bactericide- and bacteriophage-treated plants, respectively, although these differences were not statistically significant at P ≤ 0.05. Applications of bacteriophages to field-grown tomatoes decreased disease severity as measured by the area under the disease progress curve (AUDPC) by 17.5% (1997) and 16.8% (1998) compared with untreated control plants. Preharvest plant vigor ratings, taken twice during each field season, were higher in the bacteriophage-treated plants than in either bactericide-treated plants or nontreated controls except for the early vigor rating in 1998. Use of bacteriophages increased total weight of extra-large fruit 14.9% (1997) and 24.2% (1998) relative to that of nontreated control plants, and 37.8% (1997) and 23.9% (1998) relative to that of plants treated with the chemical bactericides. Chemical names used: manganese, zinc, carboxyethylene bis dithiocarbamate (mancozeb).

Free access

Abstract

In Florida, most producers of cut chrysanthemums (Dendranthema grandiflora Tzvelev.) use overhead irrigation systems and fertilize with soluble fertilizer injected through the system. Trickle irrigation can be used to produce cut chrysanthemums with substantial savings in water (2). Controlled-release fertilizers can be successfully used to produce cut chrysanthemums (1) and may be advantageous in certain production situations (3). Direct yield comparisons influenced by the four possible combinations of irrigation and fertilization practices have not been researched in previous studies. We, therefore, evaluated main and interactive effects of overhead or trickle irrigation in conjunction with soluble or controlled-release fertilization on the yield and postharvest quality of cut chrysanthemums.

Open Access

Abstract

Most of the leaf Ca collected from healthy and declining peach trees (Prunus persica L. Batsch. cv. Loring) growing on both limed and unlimed field plots was found to be non-extractable in acetic acid irrespective of leaf age, health status, or lime treatment. The concentration of extractable leaf Ca was less than 100 parts per million. Concentration of total Ca was highest in leaves from declining trees but declining trees had fewer and smaller leaves resulting in less total Ca in decline as compared to healthy trees. Large numbers of Ca-oxalate crystals were observed throughout the leaf and stem tissues. Crystals were primarily concentrated in leaf midveins. Midvein sections of leaves from decline trees contained greater numbers of crystals per unit area than did those from healthy leaves from healthy trees.

Open Access

Abstract

Increased temperature of the growing bed had no effect on fruit yield, fruit cracking, skin strength, or plant growth of tomato (Lycopersicon esculentum mill.). Yield losses from cracking were 2, 16 and 35% in the fall, spring and summer crops, respectively. The pink-fruited ‘Ohio-Indiana Hybrid O’ and ‘Missouri Hybrid 756’ had greater fruit losses due to cracking than the red-fruited ‘Floradel’ and ‘Rapids’. Large fruit were more susceptible to cracking. Fruit cracking in the fall crop was predominantly concentric in nature whereas cracked fruit in the summer was predominantly radial. Skin puncture resistance was inversely related to fruit cracking.

Open Access