Screening tomato varieties for suitability on Guam in response to the arrival of Tomato leaf curl Guam virus in the Western Region

Screening tomato varieties for suitability on Guam in response to the arrival of Tomato leaf curl Guam virus in the Western Region

Summary

This report covers the period of April 1, 2015 through March 31, 2016. At the start of the project’s second year, the dry season variety trial was underway; however, as a result of the arrival of Typhoon Dolphin to Guam the variety trial was discontinued. The top five varieties identified during the 2014 wet season variety trial were used for a final variety trial in comparison to the commonly grown variety, ‘Season Red’. A producer and professional field day was held on October 21, 2015 for local producers and agricultural experts.  The YouTube video on the Tomato Leaf Curl Guam Virus (TLCGV) is in production and will be uploaded during year three of the project.

Objectives/Performance Targets

Two of the project’s three objectives were achieved during the second year, which was to (1) improve the ability of producers to screen tomato varieties for Tomato leaf curl Guam virus (TLCGV) resistance and suitability for production on Guam, and (2) bring awareness to producers and the public about Guam’s whitefly transmitted tomato virus and steps that can be followed to reduce its impact.

These objectives were fulfilled through the following activities:

       -Partial completion of the dry season variety trial.

       -Completion of the final variety trial of the wet season variety trial top 5 varieties (Figure 1).

       -A producer and professional field day was held on October 21, 2015 where participants examined plots and                   orally evaluated the varieties (Figure 2).

       -The publication of the variety trial in the University of Guam 2015 Impact Report.

The projects third objective to bring about the adoption of farm practices will be achieved during the third and           final year through the following activities:

       -The creation of a YouTube video about TLCGV

       -Distribute TLCGV brochures at meetings of the Guam’s Farmer Cooperative Association, and Guam’s Northern          and Southern Conservation Districts.

       -Conduct a long-term outreach survey to assess changes in farmer attitude and adoption of control strategies.

       -Prepare and submit final project report.

Figure 1. Final variety trial

Figure 2. Attendees of the producer and                                                                                                                                       professional field day held on October 21, 2015.

Accomplishments/Milestones

The dry-season variety trail began on February 2015 to compare 17 commercial tomato varieties for virus resistance and production suitability against the control variety ‘Season Red’ (Table 1).  Variety trials were severely affected by the arrival of Typhoon Dolphin to Guam on May 2015, resulting in the termination of the dry-season variety trials. On June 2015, a final variety trial was conducted to re-evaluate the top 5 varieties identified in the 2014 wet-season variety trial (Table 1).

Results of the final variety trial determined the following varieties to be the producers selections for future tomato production: ‘Carmine’, ‘Tylon’, and ‘Ornela’. Producers favored these varieties over ‘Olivia’ and ‘Affinity’ because of the lack of cracking, desirable market fruit size, and high virus resistance. Although the variety ‘Olivia’ had high amount of fruit cracking, producers recommend it for production during Guam’s dry-season or in a greenhouse or hoop-house.

During a separate field investigation of tomato crops in southern fields in Guam in December 2015, symptoms characteristic of Ageratum yellow vein virus (AYVV) were observed on tomato plants in Yona, Guam. Plant samples were collected and sent to the USDA Vegetable Laboratory for analysis via Real-time PCR analysis. Real-time PCR test results showed that tomato crops were infected with AYVV. This is the first report of AYVV in southern fields of the island. Real-time PCR also identified multiple viruses in plant samples including tomato canker, tomato bushy stunt virus, potato virus X, and possibly cucumber mosaic virus, and tomato mosaic virus.

The primary obstacle encountered during the second year of the project was poor weather. Heavy rainfall in the beginning of the dry-season trial and arrival of Typhoon Dolphin in May 2015 resulted in the complete loss and termination of the dry-season variety trial. The dry-season variety trial was replaced with the final variety trial, consisting of the top five varieties selected from the wet-season variety trail conducted in 2014.

Impacts and Contributions/Outcomes

The three varieties selected by the producers from the final variety trial (‘Carmine’, ‘Tylon’, and ‘Ornela’) will be recommended for production on Guam based on their strong virus resistance, high yield and low levels of unmarketable/cracked fruits. The variety ‘Olivia’ will be recommended for production during Guam’s dry-season or in a greenhouse or hoop-house.

Other viruses identified from real-time PCR samples indicate viral infection more complex than what was previously thought. As a result it is recommended that further tomato variety trials to be conducted to identify varieties with resistance to secure local tomato production on Guam.

Collaborators: