Angular leaf spot is a common but rarely studied disease of muscadine grapes (Vitis rotundifolia Michx.) in the southeastern United States. During 1994 and 1995, we performed two field evaluations of angular leaf spot on 30 muscadine cultivars. Based on disease severity data, no cultivar was immune to angular leaf spot; however, `Albermarle', `Doreen', `Higgins', `Noble', `Regale', `Scuppernong', `Southland', and `Summit' showed high degrees of resistance. `Alachua', `Darlene', `Dixie Red', `GA-3-9-2', `Jane Bell', `Janet', `Jumbo', `Pam', and `Rosa' were susceptible.
Nancy Kokalis-Burelle, C.S. Vavrina, M.S. Reddy, and J.W. Kloepper
Greenhouse and field trials were performed on muskmelon (Cucumis melo) and watermelon (Citrullus lanatus) to evaluate the effects of six formulations of plant growth-promoting rhizobacteria (PGPR) that have previously been shown to increase seedling growth and induce disease resistance on other transplanted vegetables. Formulations of Gram-positive bacterial strains were added to a soilless, peat-based transplant medium before seeding. Several PGPR treatments significantly increased shoot weight, shoot length, and stem diameter of muskmelon and watermelon seedlings and transplants. Root weight of muskmelon seedlings was also increased by PGPR treatment. On watermelon, four PGPR treatments reduced angular leaf spot lesions caused by Pseudomonas syringae pv. lachrymans, and gummy stem blight, caused by Didymella bryoniae, compared to the nontreated and formulation carrier controls. One PGPR treatment reduced angular leaf spot lesions on muskmelon compared to the nontreated and carrier controls. On muskmelon in the field, one PGPR treatment reduced root-knot nematode (Meloidogyne incognita) disease severity compared to all control treatments.
Suzanne W. Cady, Craig K. Chandler, Daniel E. Legard, Jim F. Price, and Jim C. Sumler Jr.
The objective of this study was to compare plant health and growth in Florida fruiting fields of `Sweet Charlie' plants from 10 different plant sources. Bare-root plants from Ontario, Nova Scotia, Massachusetts, Oregon, North Carolina, Alabama, and Florida and plug plants from North Carolina and Florida were compared in a RCBD of four replicates. Plants were rated for vigor, production, diseases, and pests throughout the 1995-96 season. Crown size of transplants ranged from 7 to 12 mm. Plants from northern sources exhibited angular leaf spot (Xanthomonas fragariae) and gnomonia (Gnomonia spp.) while southern-raised plants were infected with phomopsis (Phomopsis obscurans) and anthracnose (Colletoctrichum spp.). Initial ratings confirm the potential for aphids and two-spotted spider mites (Tetranychus urticae) to be introduced on transplants. Plants from northern origins flowered 10-14 days earlier than plants produced in southern regions. Total season marketable fruit production was not statistically different among the eight bare-root treatments. Monthly fruit production was significantly different among treatments for all months except February. Performance of plug plants compared to bare-root plants of the same geographic origin were inconsistent. Initial crown size, average berry size, and cull fruit production were significantly different among the plant sources. In summary, clear differences in foliar diseases and monthly fruit production were strongly associated with transplant source. A strawberry farmer may maintain more stable production throughout the year by using transplants from several geographic origins.
Mark J. Henning, Henry M. Munger, and Molly M. Jahn
`Hannah's Choice F1' is a new, high quality eastern type muskmelon (Cucumis melo L.) with multiple disease resistance. It was developed in the Department of Plant Breeding at the Cornell University Agricultural Experiment Station in Ithaca, N.Y. It is well adapted for northeastern U.S. conditions and shows potential for good adaptation in the northwest. With multiple disease resistance it is well suited for home gardeners, market gardeners, and commercial growers. `Hannah's Choice F1' has excellent resistance to powdery mildew races 1 and 2 (Podosphaera xanthi) and some tolerance to Fusarium root rot (Fusarium oxysporum f. sp. melonis) race 2. In addition, it has resistance to watermelon mosaic virus (WMV), papaya ringspot virus (PRSV), and zucchini yellow mosaic virus (ZYMV). This is the first commercial melon to have combined resistance to these three potyviruses. Also, it has shown some field tolerance to spider mites (Tetranychus urticae). Lastly, it has shown some field tolerance to downy mildew (Pseudoperonospora cubensis), angular leaf spot (Pseudomonas syringae pv. lachrymans), and gummy stem blight (Didymella bryoniae). In 2001, 2002, and 2003 it was grown in replicated trials in New York and in 2002 and 2003 in Oregon.
As part of a program to develop transgenic highbush blueberry (Vaccinium corymbosum L.) and strawberry (Fragaria ×ananassa Duchesne) cultivars with increased levels of disease resistance, we have investigated the feasibility of introducing genes for the antimicrobial peptides cecropin B and MB39, α-thionin DB4 (DB4) and γ-thionin RsAFP1 (RsAFP1) by testing the effects of these peptides on several important pathogens of these two crop species. A thin-layer plate bioassay was conducted with these peptides and the pathogens Botrytis cinerea (Pers.ex. Fr.), Botryosphaeria dothidea (Mouq.ex. Fr.) Ces & de Not., Colletotrichum acutatum Simmonds, C. gloeosporioides (Penz.) Penz.et Sacc., C. fragariae Brooks, Monilinia vaccinii-corymbosi Reade (Honey), Phytophthora fragariae Hickman and Xanthomonas fragariae Kennedy and King. The minimum lethal concentration (μm) for cecropin ranged from 0.02 for X. fragariae strains 10 and 128 to 72.8 for C. gloeosporioides isolate Akp1. For DB4, the minimum inhibitory concentration (μm) ranged from 0.03 for X. fragariae strain 6 to 87.2 for B. cinerea isolate cc. For RsAFP1, the minimum inhibitory concentration (μm) ranged from 0.13 for X. fragariae strain 6 to 61.4 for M. vaccinii-corymbosi isolate 9423-x-45. These results indicate that introducing genes for either cecropin, DB4 or RsAFP1 into strawberry may be useful for controlling bacterial angular leaf spot disease caused by X. fragariae.
Patrick J. Conner
cultivars tested. Growers should expect to apply fungicides to control fruit rotting fungi and pick fruit promptly. Angular leaf spot ( Mycosphaerella angulata Jenkins) was observed during the late season at levels similar to the other cultivars tested
Patrick J. Conner
. Infection levels were similar to ‘Supreme’ and better than ‘Tara’, ‘Fry’, and other bronze-fruited cultivars. Angular leaf spot ( Mycosphaerella angulata Jenkins) was observed during the late season at levels similar to the other cultivars tested. ‘Lane’ is
Chad E. Finn and John R. Clark
March. Plant: vigorous; upright habit; medium to large; flowers and fruit level to above foliage; moderately tolerant of botrytis fruit rot, bacterial angular leaf-spot (Xanthomonas fragariae) , and powdery mildew, tolerant of two-spotted spider mites
Lauren Brzozowski, William L. Holdsworth, and Michael Mazourek
. 2015 ( Table 1 ) and percent foliar disease was then recorded weekly. Other minor foliar diseases, including angular leaf spot ( Pseudomonas syringae pv. lachrymans ), alternaria leaf blight ( Alternaria cucumerina ), and powdery mildew ( Podosphaera
Vance M. Whitaker, Luis F. Osorio, Natalia A. Peres, Zhen Fan, Mark Herrington, M. Cecilia do Nascimento Nunes, Anne Plotto, and Charles A. Sims
. Inoculation and rating methods for angular leaf spot (caused by Xanthomonas fragariae ), anthracnose fruit rot (caused by Colletotrichum acutatum ), charcoal rot (caused by Macrophomina phaseolina ), Phytophthora crown rot (caused by Phytophthora cactorum