Determining the Host-range and Developing Seed-treatment for Managing Bacterial Spot on Pumpkin

Project Overview

Project Type: Graduate Student
Funds awarded in 2010: $10,000.00
Projected End Date: 12/31/2012
Grant Recipient: University of Illinois
Region: North Central
State: Illinois
Graduate Student:
Faculty Advisor:
Mohammad Babadoost
University of Illinois

Annual Reports


  • Vegetables: cucurbits


  • Crop Production: crop rotation
  • Education and Training: workshop
  • Pest Management: biological control, biorational pesticides, chemical control, cultural control, genetic resistance, integrated pest management
  • Production Systems: general crop production

    Proposal abstract:

    Pumpkin is a high-value crop grown throughout the United States (US). Approximately 1.5 billion pounds of pumpkins are produced in the US every year and Illinois with about 25,000 acres ranks first in pumpkin production in the US. More than 90% of processing pumpkin are grown and processed in Illinois. Bacterial spot, caused by Xanthomonas cucurbitae has become one of the most economically important diseases on pumpkins and a serious threat to the industry. Leaf spots and fruit lesions and rot are major symptoms of this disease, causing up to more than 75% yield losses. In the past five years, the disease has become more prevalent in Illinois and other Midwestern states and many growers complain about the yield losses and of lack of effective disease management measures. Developing effective management of bacterial spot of pumpkin has not been feasible because of lack of sufficient information on the etiology of the disease, especially on the host-range and seed-borne aspect of the pathogen. This is proposal for a two-year project to generate necessary information on the etiology of bacterial spot of pumpkin and develop effective methods for management of the disease. The specific objectives of this research are to: (1) identify the host-range of X. cucurbitae; (2) determine the importance of seed-borne aspect of the pathogen; and (3) develop management of the disease, emphasizing effective seed-treatments and cropping rotations. Result of this study will be presented to growers, industry personnel, extension educators, students, and scientists at the local, statewide, regional, and national meetings. The results also will be published in the newsletters, websites and refereed-journals.

    Project objectives from proposal:

    Project Outcome. The short-term outcome of this study will be determining host-range among the crops grown in rotation with pumpkin and weeds that grow in the pumpkin fields. Another short-term outcome will be elaboration of the plant infection of plant from the seed-transmitted bacteria. The intermediate- and long-term outcome of the study will be developing effective seed treatments using heat and/or chemicals and cropping rotations for management of the disease. Approach, Activities, Methods and Inputs. In order to identify host range of X. cucurbitae, five known isolates will be used, the inocula of these isolates will be prepared separately, the inocula will be mixed together and inoculated onto the plants at 4-week-old, 8-week-old, and 12-week-old growth stages using the method described by Babadoost and Ravanlou (3). All 36 crops grown in rotation with pumpkin in Illinois, and all nine weed species that commonly grow in pumpkin fields (16), will be tested to determine whether or not they are hosts of X. cucurbitae. The studies will be conducted in plant growth chamber, a greenhouse, and in the fields. During 2011-2013, at least six pumpkin commercial fields in each of northeast, southeast, southwest, and northwest regions of Illinois will be visited during mid-season to harvest. Ten infected pumpkin fruits will be collected from each field. Seeds of the fruits will be collected separately and dried on a laboratory bench. Collected seed will be tested for presence of X. campestris using the following methods: (1) wash the seed in saline solution for 10 min on a shaker and the seed-wash will be plated in semi-selective culture medium; (2) surface-sterilize the seed for 2-min in 0.5% NaClO solution, wash the NaClO-treated seeds in sterile-distilled water (SDW) twice to remove the NaClO residue, wash the surface-sterilized seeds in saline for 10 min on a shaker, and plate the seed wash; (3) plate the seeds (5 seeds/plate) on a semi-selective culture medium; and (4) surface-sterilize the seed for 2-min in 0.5% NaClO solution, wash the surface-sterilized seeds with SDW twice, and plate the seed (5 seeds/plate) on a semi-selective culture medium. Semi-selective culture medium will be the medium developed by Kuan et al. (1985) for studying X. carotae (8). Other culture media may be used as needed. For each tests mentioned above, 100 seeds, or as available, will be used. The plates will be incubated at 28?C for 4 days or longer. The growing bacterial colonies will be sub-cultured and identified based on the traditional (9,15) and molecular (9,11)methods. Pathogenicity of representative isolates will be determined as described by Babadoost and Ravanlou (3). Infected seeds will be germinated in test tubes in the laboratory, in a plant growth chamber, in pots in a greenhouse, and in one or more well-isolated fields to study the process of bacteria from seeds to seedlings and true leaves and development of the bacterial spot on the leaves and fruits. Development of effective seed treatment for eradication of seed-borne inoculum will be through hot-water treatment (45-55?C), use of NaClO solution, and chemicals (e.g., antibiotics), as described by Babadoost et al. (1), Franc (6), and Lewis and Miller (10).

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.