Final report for OW19-344
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 worked 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. A total of 511 symptomatic samples were collected from 42 locations across Hawai'i State, with 468 samples yielding identification of potential causal agents. The project team conducted laboratory tests of varietal resistance and susceptibility for three diseases identified as major concerns for Hawai‘i breadfruit production - Colletotricum, Fusarium, and Phytophthora. Four strains of each of these genus were applied to the fruit and seedlings of five varieties in controlled settings. Varieties demonstrated significant differences in susceptibility to Fusarium and Phytophthora, but no symptoms were observed from the inoculations of Colletotricum. Findings were coupled with literature review and interviews with experts to produce an extension publication, technical factsheet, and outreach efforts to disseminate results. Results inform grower recommendations for varietal selection in Hawai‘i. These materials have and 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 Phytomycology 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 five breadfruit varieties to three 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.
Collection of infected fruit and laboratory identification of diseases will be ongoing from the start of the project in July 2019 until January 2021. The research trials for Objective 2 will start in July 2020 and be completed by January 2021. The graduate student will work with the PI to analyze the research results and write the academic article until May 2021, when the article will be submitted for publication. Using results from Objective 2, the PI will develop varietal
recommendations for Hawai‘i which will be completed by January 2020. The Technical Factsheet on breadfruit disease with photographs and observational descriptions will be completed by April 2021. The varietal recommendations and Technical Factsheet will be disseminated to networks in May and June 2021.The HUPC manager will organize and promote 2 workshops on O‘ahu and Hawai‘i Island between April and May of 2021. The PI will lead both workshops and collect surveys by June 2021. Results of the surveys will be compiled for the final grant report in July 2021.
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Objective 1: Catalog Breadfruit Diseases.
The foundational objective to the project was to better understand the prevalence and severity of breadfruit diseases in Hawai’i in order to assess their risk to the growing industry, inform future research, and begin to develop best management practices.To effectively accomplish this objective, we leveraged our well-established farmer network to source diseased material from multiple farms across the state. Outcomes from a prior Western SARE grant (SW17-050) included the establishment of social media platforms to encourage farmer-to-farmer sharing regarding the cultivation of breadfruit. This was met with exceptional success, and our private online group (“Breadfruit Growers”) now consists of 828 members – about 400 of which are located in Hawai’i, with the remainder joining from national and international locations. This network, in addition to our more direct relationship with a number of breadfruit growers, was leveraged in order to receive reports of breadfruit diseases throughout the state. Farmers sent us pictures of diseased breadfruit trees or fruit from their farm, and we then either (1) visited farms to collect samples in person, or (2) coordinated with farmers to document the in-field conditions and mail us samples. A research technician was hired and trained in the Phytomycology Laboratory by co-PI Uchida. Between July 2019 and December 2020, samples were received, classified into categories based on the physical symptoms, and cultured for morphological identification. The expanding edge of the symptoms were sampled, surface sterilized, and cultured on sterile media. From the cultures, single hyphal tips were isolated and grown to maturity in order to identify the isolate through spore morphology. Through this process, fungi were considered potential causal agents if (1) the same fungus is repeatedly cultured from similar symptoms and (2) the fungus is a known pathogen of similar symptoms in other plants.
Objective 2: Varietal Resistance to Disease. In order to confirm pathogenicity and explore the relative susceptibility of breadfruit varieties, fruit and seedlings were inoculated with pure cultures of the suspected causal agents that were collected in Objective 1. Three diseases were tested: Phytophthora, Colletotrichum, and Fusarium. For each disease four separate isolates/strains of the causal agent were used. Five breadfruit varieties were tested: Puou, Maafala, Maoli, Otea, and Fiti. For each test, five fruit and five seedlings were subjected to inoculation. Fruits were washed, dried, marked for identification, and placed in individual containers. One drop of inoculum (spores in water at one million spores per ml) was applied. Fruits were 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 were taken, and the rate of disease spread analyzed. After more than 50% fruit rot was evident, fruit samples were used to isolate the pathogen to confirm pathogenicity.
Objective 3: Develop Technical Factsheet and other publications. Based on (1) results from our studies, (2) an extensive literature review, and (3) interviews with 12 local disease and breadfruit experts, an extension publication was developed. A graduate researcher conducted the compilation of existing literature regarding breadfruit diseases and, in coordination with PI Lincoln, identified and conducted the 12 expert interviews. The publication was drafted by PI Lincoln, and reviewed and edited by six co-authors, three external plant pathology experts, and four breadfruit producing organizations. The extension publication and technical factsheet will be permanently hosted on the College of Tropical Agriculture and Human Resources (CTAHR) website, with physical copies available by request to CTAHR.
A scientific publication is being drafted by PI Lincoln for publication with the target journal of Plant Disease.
Objective 4: Conduct 2 on-farm workshops. Due to the COVID-19 pandemic and the difficulties in conducting in-person outreach this past year, this deliverable was slightly modified to conduct a single on-farm workshop, to present at a hybrid (in-person/online) meeting of the Hawai’i ‘Ulu Producers Cooperative, and to create a short extension video that can be distributed more widely.
Objective 1: Catalog Breadfruit Diseases.
A total of 511 samples were received from 42 different growers across the state, with 468 samples yielding identification of likely causal agents (Table 1). The resolution was inadequate to explore spatial or temporal patterns to the diseases, but the extensive documentation of the symptoms and likely causal agents provided important knowledge about how prevalent and potentially damaging the different diseases were.
Objective 2: Varietal Resistance to Disease.
No infection establishment was observed for Colletotrichum in any treatment. It is possible that this is not an infectious agent, or perhaps the method of inoculation was insufficient. Given the commonality of symptoms that we isolated Colletotrichum from and the consistency from which Colletotrichum was the sole potential pathogen associated with the symptoms, we believe that Colletotrichum is a pathogen associated with fruit and leaf anthracnose despite not seeing results from inoculation. Further investigation and trials are needed here, as the symptoms we associated with Colletotrichum were among the most prevalent across the state. Fusarium demonstrated low levels of infection for seedlings only, with no symptoms established on inoculated fruit. Although Fusarium was associated with some fruit spotting in the field, it was selected for testing due to its prevalence in stem rot and leaf withering. Similar symptoms were observed and re-isolated from the inoculation trial, confirming its pathogenicity. All varieties had relatively low incident of take, with ‘Otea’ and ‘Puou’ varieties having the highest incidences. Finally, Phytophthora showed establishment on all varieties for both seedling and fruit, with incidence ranging from 5% to 95%. Clear varietal differences were apparent, with ‘Maafala’ and ‘Otea’ varieties demonstrating lower susceptibility, and ‘Puou’ demonstrating very high susceptibility. These findings further support field observations of a large phytophthora outbreak that occurred in Waiahole Valley in 2018, where all the ‘Puou’ trees in the valley died, ‘Maoli’ exhibited extreme fruit loss but no tree dieback, and ‘Maafala’ exhibited reduced levels of both fruit and tree losses. These results contradict current knowledge that suggests smooth skinned varieties are less susceptible than rough-skinned varieties, as ‘Fiti’, a very smooth skinned variety, demonstrated relatively high susceptibility.
Objective 3: Develop Technical Factsheet and other publications.
The extension publication includes (1) the history of breadfruit disease outbreaks globally, (2) a description of known breadfruit pathogens, description of their symptoms, and an assessment of their threat, and (3) chemical, biological, and cultural methods of managing diseases in breadfruit production. As an appendix, the publication includes a Technical Factsheet that summarizes identification and management of the most common and/or threatening breadfruit diseases in Hawai’i. The publication is currently in press with the College of Tropical Agriculture and Human Resources, hopefully to be officially released in the next 1-2 months. Drafts of this document have been distributed to growers as requested and during outreach, and an “in-press” version of the documents are included as an appendix to this report.
Objective 4: Conduct 2 on-farm workshops.
The on-farm workshop was held at “Ulu Bros” farm on Maui Island May 15th, 2021. The location is part of a 400-acre agricultural parks, and includes 6 farms with breadfruit. This workshop was attended by 18 participants, one of which was a breadfruit processor. We were able to tour three farms in the agricultural park and observe disease incidence in the field, highlight the various diseases and management techniques, and allow for farmer-to-farmer sharing of issues and solutions in terms of breadfruit diseases. This workshop was conducted by PI Lincoln, as Co-PI Isele resigned from his position due to personal reasons. An electronic version of the Western SARE evaluation tool, compiled in Google Forms, was disseminated to workshop participants after the fact.
An overview of this work and dissemination of the draft extension publication was also presented at the Hawai’i ‘Ulu Producers annual membership meeting on June 17th, 2021, with representatives from 85 breadfruit farms in attendance. This was not so much a workshop, as it was a brief summary of the work conducted and a dissemination of the draft extension publication and technical factsheet. At this meeting a contact list was generated for farmers interested in a breadfruit disease workshop once concerns of COVID abate.
Finally, an extension video on breadfruit disease and management was produced in partnership with the Hawai’i ‘Ulu Producers Cooperative. A seven-minute script was devised that condenses the findings of this project into an easily digestible format, and directs viewers to the permanent home for the associated written publications. The footage for the video was shot in June 2021, and the approved extension video is expected to be released in October 2021.
During the project period, we also conducted a four-part virtual series on breadfruit in partnership with Kahumana Farms, and presented virtually on breadfruit orchard management at the Hawai’i Tropical Fruit Growers Association’s annual conference.
Educational & Outreach Activities
Approximately 40 consultations were conducted, including 4 on-farm consultations, approximately 12 phone call consultations, and approximately 25 email consultations.
One extension publication was created, to be published and hosted, permanently and for free, at the College of Tropical Agriculture and Human Resources. One factsheet was created that is included as an appendix to the extension publication. One educational video was filmed and is in the process of being created, that will be jointly hosted by the College of Tropical Agriculture and Human Resources, and the Hawai'i 'Ulu Producers Cooperative.
One scientific journal article is in preparation by PI Lincoln, in partnership with a previously unpublished breadfruit disease study conducted by Takena Redfern, with the target journal of Plant Disease.
A four-part online series for breadfruit production, including breadfruit disease and disease management, was conducted in partnership with Kahumana Organic Farms in Jan, April, July and September of 2019, each of which was attended by 40-50 participants. An pre-recorded presentation on breadfruit diseases was given for the Hawai'i Tropical Fruit Growers Association for their annual conference in October 2020, watch by an unknown amount of viewers, followed by an online Q&A session attended by about 40 individuals.
One on-farm workshop was conducted at “Ulu Bros” farm on Maui Island May 15th, 2021, attended by 18 participants (16 farmers, 1 processor, and 1 agricultural professional).
A short, summary presentation and dissemination of the draft extension publication and technical factsheet was given at the Hawai'i 'Ulu Producers Cooperative's annual meeting, attended by 85 breadfruit farmers.
PI-Lincoln has continued to curate and grow the online 'Breadfruit Growers" groups, which enrollment now stands at 862 individuals. Through this page we have posted on our continued research progress and disseminated results real time, as well as responded to several hundred individual questions and comments posted in the group to help get factual information to breadfruit growers within Hawai'i (approximately 400 individuals) and outside of Hawai'i (approximately 450 individuals).
Orchard management for reduced fungal disease risk
Project has thus identified 13 associated genus as potential fungal pathogens of breadfruit and explored the relative resistance of five common breadfruit varieties in Hawai'i. Currently, to our knowledge no breadfruit growers use fungicides on their plants, and losses from diseases are generally accepted. Farmers have indicated that our research and education conducted in this grant has been of high value, and several have or have indicated that they will include sustainable disease management strategies in their orchards. At least one farmer has altered his plaanting plans to include more disease resistant varieties, and a number of farmers have indicated that they plan to implement some of the integrated disease management strategies to reduce disease incidence on their 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.
We administered the SARE evaluation sheet after conducting the one on-farm workshop held as part of this grant. While we only received 6 total responses, the responses were overwhelmingly positive. We have attached one representative sample each for a farmer and professional to this report. Survey 2021
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 had proposed this work in a long-term Western SARE Research and Education project to build upon the foundation we are establishing with the current project, but unfortunately were not funded. We may resubmit that proposal to continue this work in partnership with USDA ARS researchers.