Breadfruit Disease Identification and Varietal Resistance in Hawai‘i
Breadfruit (Artocarpus altilis) plantings in Hawai‘i are growing exponentially, as research indicates over 2,500 trees have been established on commercial farms in the past 5 years and total plantings are expected to double further in the next 5 years (Langston and Lincoln 2018). A statewide assessment identified over 150 farms growing breadfruit and over 5,000 agricultural trees representing an estimated $1.5 million farm gate price once mature. This rapid development requires increased vigilance in disease monitoring to prevent crop losses and protect farm profitability. Diseases of breadfruit have caused widespread tree decline and death in Jamaica and the Pacific Basin (Trujillo 1971, Coates-Beckford and Pereira 1992), threatening local food production and the commercial breadfruit industry. This project addresses gaps in research on breadfruit diseases in Hawai‘i as well as varietal susceptibility and resistance to pathogens of the greatest concern.
PIs will work with the Hawai‘i ‘Ulu Producers Cooperative and individual growers to identify and catalog Hawai‘i breadfruit diseases using producer reports, photographs, infected sample collection, and lab cultures. The project team will also conduct laboratory tests of varietal resistance and susceptibility for four diseases identified as major concerns for Hawai‘i breadfruit production. Findings will be submitted for publication in a scientific journal and used to create a technical factsheet for producers with disease catalog and visual guide to pathogen identification. Results will also be used to develop grower recommendations for varietal selection in different regions of Hawai‘i. These materials will be shared with producers and an extended network of international breadfruit researchers, producer groups and commercial manufacturers. While a relatively simple design and project, virtually no previous research has systematically confirmed pathogenicity for breadfruit diseases or examined differences in cultivar susceptibility (Lincoln et al 2018).
Through farmer network, identify and catalogue diseases affecting breadfruit (Artocarpus altilis) in Hawai‘i using reports from growers, photographs, infected sample collection, and lab cultures.
July 2019 – January 2021
Materials Produced: Hawai‘i Breadfruit Disease Catalog
Field technician will work with farmer network to ship samples of infected fruit to
CTAHR laboratory where PIs Lincoln and Uchida will isolate, culture, and identify diseases. Collected diseases will be documented through farmer and PI photographs, field observations, and lab findings.
Conduct trials to determine susceptibility or resistance of breadfruit varieties to four major diseases in Hawai‘i, including Phytophthora and Colletotrichum.
June 2020 – January 2021
a. Materials Produced: Published scientific article
b. Field technician will work with statewide breadfruit farmer network to ship healthy
fruit from range of varieties and locations to CTAHR lab. Overseen by PIs,
graduate assistant will inoculate fruits with selected diseases in lab and
document deterioration speed and scope. In collaboration with project PIs,
graduate assistant will analyze research data and publish a scientific article
based on the study.
3. Develop and share Technical Factsheet on breadfruit diseases in Hawai‘i, including varietal resistance and susceptibility recommendations for specified diseases.
January 2021 – April 2021
Materials Produced: Technical Factsheet on breadfruit disease in Hawai‘i
Based on findings from Objective 2 above, PI Lincoln will develop varietal
recommendations for Hawai‘i breadfruit growers. He will compile recommendations, disease documentation and photographs into a Technical Factsheet to help producers identify disease in their breadfruit trees. PIs will disseminate Factsheet to farmer and extension network.
4. Hold 2 on-farm workshops on breadfruit disease identification and management on major islands with commercial production, Hawai‘i and O‘ahu.
May 2021 – June 2021
a. PIs will lead two workshops on breadfruit disease identification on Hawai‘i Island and O‘ahu, distribute Technical Factsheet to participants, and evaluate participant subject knowledge before and after using SARE-approved surveys.
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Through grower outreach and farm visits, the field technician will work with farmers to scout for disease in breadfruit trees. Incidences of potential infection will be documented through recorded observations and photographs. Diseased material will be collected in the field by the technician, sealed in airtight plastic bags, and transported via overnight shipping to the Phytomycology laboratory at the University of Hawai‘i in Ma?noa for analysis by PIs Lincoln and Uchida. In the lab, material from the edge of diseased areas will be dissected, sterilized and grown out on water agar. Single hyphal tips will be transferred to nutrient agar to establish pure cultures. Spores form the pure cultures will be studied and fungi will be identified based on spore morphology. Following identification, pathogenesis will be determined by growing the inoculum and spreading it on test fruits and/or plants and observing disease development. From disease development, disease will be re-isolated using above methods to confirm pathogenicity (what we put in is what we get out). Along each stage of collection, grow out, and disease development, photographic documentation will be conducted.
Using isolated and confirmed pathogens from Objective 1, trials for disease resistance or susceptibility of fruit from multiple breadfruit varieties will be conducted. We have budgeted to examine six breadfruit varieties (based on those most prevalent among current producer partners, such as Hawaiian Ulu, Maafala, Ulu fiti, Otea, Puou and Lipet) and four prevalent diseases affecting breadfruit in Hawai‘i (which we anticipate to be Monilia, Phytophthora, Colletotrichum, and Mucor; Ploetz 2003). For each disease-variety combination, six fruits will be inoculated with each disease in the laboratory (a total of 144 fruits). Fruits will be washed, dried and placed in individual plastic containers. Fruits will then be marked, and one drop of inoculum (spores in water at 1 x 106 spores/ml) will be applied. Fruits will be incubated for 24 hours at 100% humidity for spore germination and disease initiation, then maintained at field conditions in the laboratory. Daily measurements and photos will be taken to analyze rate of disease development. After more than 50% fruit rot is evident, isolation of disease will be made to confirm the pathogen. Assessment of disease resistance or susceptibility will be based on average percent take and rate of lesion development.
The PIs and graduate student researcher will develop a Technical Factsheet cataloguing breadfruit diseases in Hawai‘i with photographs and observational descriptions, serving as a visual guide to teach farmers how to identify infections on their farm. In addition, the PI will develop varietal recommendations for different climates or regions of the state based on the findings of the disease trial (Objective 2). This Technical Factsheet will be published through CTAHR extension and publicized through various farmer-to-farmer, agricultural nonprofit and extension networks. Further, PI Isele will work directly with growers across the state to disseminate results through on-site farmer visitations and training of the extension agent network represented by CTAHR.
A publication documenting the quantified differences in disease resistance of the six breadfruit varieties tested in Objective 2 will be published in a peer-reviewed scientific journal such as Virology and Mycology, Plant Pathology, or the Journal of Plant Sciences and Agricultural Research.
PI Shapiro will organize and promote 2 on-farm disease identification workshops on Hawai‘i Island and O‘ahu, the two islands with greatest commercial production and industry growth to date. PIs Lincoln and Isele will lead the 2 workshops as primary presenters. The Technical Factsheet with varietal recommendations will be printed and distributed to workshop participants.
Educational & Outreach Activities
So far most of the work has focused on Objective 1, which is collecting, culturing, and cataloging the diseases. We have visited multiple farms and discussed general disease management practices as we collected, but have not yet conducted targeted outreach and dissemination yet. One talk was given in the department regarding the current results of the work.
Orchard management for reduced fungal disease risk
Project has thus identified over 20 associated fungal pathogen with breadfruit diseases, as well as collecting anecdotal observations about the prevalence and diversity of diseases across farms. The emerging breadfruit industry in Hawai’i is powered primarily by small diversified farms that rely heavily on high quality production. The development best-practice management of breadfruit will considerably contribute to the economic sustainability of diversified farms in Hawai’i. Subsequently, both environmental benefits from the tree cultivation and diversified agriculture will be realized, as well as social benefits of supporting small and local family farmers.
It is not necessarily a success story unfortunately, but a story that does indicate the pressing need for this work. A massive phythophthora outbreak (we identified the disease through our culturing efforts) in one valley on O’ahu (Waiahole Valley) saw the total loss of one thirty tree orchard. It has been the first time that we have seen a total orchard death in our five years of working with breadfruit farmers. Other farmers in the valley saw nearly 100% fruit rot on some varieties, while other varieties did not suffer. One success is that we were able to document this horrendous disease outbreak and can use it to inform other farmers’ practices.
We have determined that while this project will make substantial contribution to the disease management of breadfruit, better spatial and temporal coverage, as well as more detailed ID (genetic ID vs optical ID) would greatly improve the project findings. We have proposed this work in our long-term Western SARE Research and Education project to build upon the foundation we are establishing with the current project.