We report the use of nuclear magnetic resonance (NMR) imaging to detect differences in invasion and colonization of fruit by pathogens (Botrytis cinerea, Colletotrichum acutatum, and Phytophthora cactorum), and bruise wounds are sharply distinguishable from healthy fruit tissue by their T1 times. Digitized images from T1 images clearly show two or more zones of pathogen activity in fruit tissue. The innermost zone corresponds to the area of greatest invasive activity at the leading margin of the infection. A second zone corresponds to the area of tissue that has been killed and is being degraded by the pathogen. Sometimes, a third zone is present at the outer border of the lesion and this correspond to where aerial sporulation may occur. Images of bruises, however, are uniform with no apparent gradations in T1 characteristics. Detection of fruit deterioration and decay is important in understanding and controlling postharvest loss of fruit crops. The nondestructive nature of MRI provides a means to quantify the process of decay development and control measures applied to fruits.
John L. Maas and M.J. Line
J. Song, R. Leepipattanawit, W. Deng and R.M. Beaudry
Hexanal vapor inhibited hyphae growth of P. expansum Link. and B. cinerea Pers. on PDA media and on apple slices. After 48 hours exposure to 100 μl·liter–1 hexanal, the hyphae growth of both fungi was ≈ 50% that of nontreated controls. At a concentration of 250 μl·liter–1, neither fungi grew during the treatment period, however, some growth of both fungi occurred 120 hours after treatment. At concentrations of hexanal vapor of ≥450 μl·liter–1, the growth of both fungi ceased, and the organisms were apparently killed, neither showing regrowth when moved to air. When fungi were allowed to germinate and grow for 48 hours in hexanal-free air, a subsequent 48-hour exposure to 250 μl·liter–1 hexanal slowed colony growth relative to controls for several days and a 48-hour exposure to 450 μl·liter–1 stopped growth completely. Concentrations of hexanal that inhibited fungal growth on PDA also retarded decay lesion development on `Golden Delicious' and on `Jonagold' apple slices. Hexanal treatment stimulated aroma volatile production in `Jonagold' and `Golden Delicious' apple slices with hexanol and hexylacetate production strongly enhanced after 20 to 30 hours of treatment. A small amount of butylhexanoate and hexylhexanoate production also was noted. Since hexanal was converted to aroma-related volatiles by the fruit, the possibility of developing a system for nonresiduel antifungal agent is promising. This possibility was examined in modified-atmosphere packages.
Todd L. Mervosh and James A. LaMondia
The effects of terbacil herbicide on strawberry (Fragaria ×ananassa Duch. `Honeoye') yield and black root rot disease were determined in field plots at two locations in Connecticut over 4 years. Terbacil treatments at up to four times the maximum label dosage caused some temporary foliar chlorosis but did not affect the health of structural or perennial roots and associated feeder roots. Development of secondary root growth (perennial roots) was not influenced by terbacil. Terbacil had no effect on the quantity of lesion nematodes [Pratylenchus penetrans (Cobb) Filip & Schur. Stek.] extracted or the amount of the fungal pathogen Rhizoctonia fragariae Husain and McKeen isolated from strawberry roots. At both locations, R. fragariae was common on plant roots by the fourth year. Terbacil treatments did not affect strawberry yields in terms of number or weight of ripe berries per plot. Our results indicate that terbacil does not contribute to black root rot or decreased yields in `Honeoye' strawberry. Chemical name used: 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4-(1H,3H)-pyrimidinedione (terbacil).
Joseph W. Kloepper, M.S. Reddy, Choon-min Ryu and John F. Murphy
Use of beneficial rhizobacteria to enhance growth and induce systemic disease protection in transplants. Plant associated bacteria have been studied for the capacity to provide plant growth enhancement and biological disease control. “Rhizobacteria” are bacteria from the rhizosphere that have the capacity to colonize plant roots following introduction onto seeds or into soil. Effects of rhizobacteria on plants may be deleterious, neutral, or beneficial. Beneficial rhizobacteria are termed “PGPR—plant growth-promoting rhizobacteria.” In developmental studies aimed at reducing to practice the concept of induced systemic disease protection mediated by PGPR, we discovered that mixtures of PGPR and an organic amendment into the soilless media used to prepare tomato transplants resulted in highly significant and reproducible plant growth promotion. Time for development of transplants was typically reduced from 6 weeks for controls receiving industry standard fertility and growth regimes to 4 weeks for seedlings grown in soilless mix into which the PGPR had been incorporated. This marked growth promotion was also associated with systemic protection against pathogens. When transplants were inoculated with the tomato spot pathogen, significantly fewer lesions developed on plants grown in the biological system than on control plants. Similar effects on plant growth and systemic disease protection were seen with cucumber, bell pepper, and tobacco, suggesting that the benefits are not highly crop or cultivar specific. Results of recent field studies will be presented. We conclude that incorporation of PGPR into soilless mixes is a technologically useful and feasible way to deliver benefits to transplants.
Diana L. Lange and Arthur C. Cameron
The effect of controlled atmospheres (CA) on the development of injury symptoms and storage life of sweet basil (Ocimum basilicum L.) cuttings was assessed. Three-node basil stem cuttings were placed in micro-perforated low-density polyethylene packages and stored in the dark at 20 °C in a continuous stream of nitrogen containing the following percentages of O2/CO2:21/0 (air), 21/5, 21/10, 21/15, 21/20, 21/25, 0.5/0, 0.5/5, 1/0, 1.5/0, 2/0, 1/5, 1.5/5, 1.5/7.5, and 1.5/10. Cuttings stored in an atmosphere of <1% O2 developed dark, water-soaked lesions on young tissue after only 3 days. Fifteen percent or more CO2 caused brown spotting on all tissue. Sweet basil stored in 1.5% O2/0% CO2 had an average shelf life of 45 days compared with 18 days for the air control. None of the CA combinations tested alleviated chilling injury symptoms induced by storage at 5 °C.
Shiming Xue, Robert H. Bors and Stephen E. Strelkov
the Agricultural Development Fund of Canada as part of a research project.
Drew C. Zwart and Soo-Hyung Kim
been suggested and research to date is limited ( Elad et al., 2011 ; Lehmann et al., 2011 ). The objective of the present study was to determine if biochar amendment of a soilless potting media can reduce the development and impact of stem lesions
Michelle A. Grabowski and Dean K. Malvick
rated as the number of flowers infected at 6 and 19 DAI, and as the lesion length on the flower stalks 28 DAI. The trial was conducted twice. Susceptibility of below ground storage organs in controlled environment. Rhizomes of ‘Tropical White’ canna were
John R. Stommel and Kathleen G. Haynes
Anthracnose, caused by Colletotrichum coccodes, is a serious ripe tomato fruit rot disease. Genetic resistance to anthracnose is not available in commercial tomato cultivars, but has been reported in small-fruited Plant Introductions (P.I.), and with lesser intensity in a number of breeding lines. Transfer of high levels of resistance from these breeding lines or P.I.s to elite materials has proven difficult. Inheritance of resistance has been described as complex with at least six loci influencing resistance reactions. Segregating populations originating from a cross between a susceptible tomato breeding line and a large-fruited breeding line (88B147) with resistance derived from Lycopersicon esculentum var. cerasiforme P.I. 272636, were evaluated for anthracnose resistance. Analysis of anthracnose resistance in puncture-inoculated fruit indicated small, but significant, additive genetic effects for resistance. Additional populations were developed from crosses of a susceptible inbred processing tomato cultivar with: 1) the resistant P.I. 272636, 2) an unadapted small-fruited resistant line developed from P.I. 272636, and 3) the large-fruited breeding line 88B147, also with resistance derived from P.I. 272636. Small additive effects identified in large-fruited material, in comparison to the resistant P.I., suggests that resistance loci have been lost during germplasm development. This is consistent with the relatively larger lesions observed in large-fruited lines derived from P.I. 272636. Positive correlations were noted between small fruit size and high levels of anthracnose resistance. Identification of molecular markers linked to resistance genes in the respective populations will be discussed.
Muhammad Imran Al-Haq, Y. Seo, S. Oshita and Y. Kawagoe
The fungicidal effectiveness of electrolyzed oxidizing (EO) water on peach [Prunus persica (L.) Batsch.] fruit was studied. Fruit were inoculated with a spore suspension of 5 × 105 conidia/mL of Monilinia fructicola [(G. Wint.) Honey] applied as a drop on wounded and nonwounded fruits, or by a uniform spray-mist on nonwounded fruits. Fruit were immersed in tap water at 26 °C for 5 or 10 minutes (control), or treated with EO water varying in oxidation-reduction potential (ORP), pH, and free available chlorine (FAC). Following treatment, fruit were held at 20 °C and 95% relative humidity for 10 days to simulate retail conditions. Disease incidence was determined as the percentage of fruits showing symptoms of the disease, while severity was expressed as lesion diameter. EO water did not control brown rot in wound-inoculated fruits, but reduced disease incidence and severity in nonwound-inoculated peach. Symptoms of brown rot were further delayed in fruit inoculated by a uniform-spray mist compared with the nonwounded-drop-inoculated peaches. Fruit treated with EO water held for 8 days at 2 °C, 50% RH, did not develop brown rot, until they were transferred to 20 °C, 95% RH. The lowest disease incidence and severity occurred in fruit immersed in EO water for up to 5 minutes. EO water having pH 4.0, ORP 1,100 mV, FAC 290 mg·L-1 delayed the onset of brown rot to 7 days, i.e., about the period peach stays in the market from a packing house to consumer. No chlorine-induced phytotoxicity was observed on the treated fruit. This study revealed that EO water is an effective surface sanitizer, but only delayed disease development.