Location: Tropical Crops and Germplasm Research
2024 Annual Report
Accomplishments
1. Yield and fruit quality traits of rambutan cultivars grafted onto three rootstocks and grown in a Mollisol soil in Puerto Rico. The globalization of the economy, increased ethnic diversity and a greater demand for healthy and more diverse food products have opened a window of opportunity for the commercial production and marketing of tropical fruit, including rambutan. Little is known about the performance using various scion/rootstock combinations in the tropics and subtropics. A study conducted by ARS scientists in Mayaguez, Puerto Rico evaluated yield performance and fruit quality traits of three cultivars (‘Gula Batu’, ‘Jitlee’, ‘R-162’) grafted onto three rootstocks (‘Binjai’, ‘Gula Batu’, ‘R-134’) in an alkaline Mollisol soil in Santa Isabel, Puerto Rico. Overall, scion/rootstock treatments exhibited an increase in fruit number and yield from 2011 to 2015. Cultivar ‘R-162’ grafted onto ‘Gula Batu’, had the highest 5-year mean for number (289,911 fruits) and yield (8,260 kg/ha) of fruit. Regardless of rootstock, ‘R-162’ had higher number of fruit and yield. All cultivars produced more fruit and had higher yield when ‘Gula Batu’ was used as a rootstock. Scion/rootstock treatments did not have a significant effect on individual fruit weight. Cultivar ‘R-162’ grafted onto ‘Gula Batu’ had higher soluble solids concentration but it was not significantly different than the rest of the treatments except for ‘Gula Batu’ grafted onto ‘Binjai’ and ‘Gula Batu’ grafted onto ‘R-134’ which had significantly lower soluble solids concentration. This study provides for the first time useful information to Extension Agents and growers about yield and fruit quality traits of various scion/rootstock combinations and specifically demonstrating cultivar ‘R-162’ being a highly productive cultivar and ‘Gula Batu’ a superior rootstock by performing very well under alkaline soil conditions.
2. Coffee fruit rot distribution, ecology and associated fungi. Coffee fruit rot (CFR) is one of the most important diseases affecting coffee worldwide. This disease is well known in Africa as coffee berry disease (CBD). The disease is characterized by external necrosis and sunken dark brown spots on green or mature coffee fruits that eventually become mummified. In Puerto Rico, coffee fruit rot has been present for many years, but has yet to be quantified. This study conducted by ARS researchers at Mayaguez, Puerto Rico and University of Puerto Rico scientists surveyed the incidence and severity of CFR, and correlated these to environmental parameters, cultivation methods (sun vs shade), presence of the coffee berry borer (CBB), and fruit rot-causing fungi. This study showed that CFR is present throughout Puerto Rico at varying altitudes and environmental and cultivation factors are associated with its incidence and severity. Specifically, increased altitude and shade significantly correlated with lower CFR disease incidence. In addition, fruits damaged by the CBB were found to have higher disease incidence than undamaged fruits. Coffee fruit rot was associated with seven fungal genera with Colletotrichum spp. and Fusarium spp. being the most prevalent suggesting that there is a microecosystem complex on the fruit surface and pulp of coffee fruits. This study is important because planting coffee at higher altitude under shade and controlling CBB can potentially reduce CFR incidence.
3. Coffee fruit rot in Puerto Rico: New associations with Colletotrichum spp., Fusarium spp. and the coffee berry borer. Coffee fruit rot (CFR) is an important disease that affects coffee production and quality. Several Colletotrichum species have been reported causing CFR worldwide. In Puerto Rico, four species of this pathogen were detrimental to coffee fruits. However, the role of Fusarium species affecting coffee was also suggested but pathogenicity tests were not conducted. A study conducted by ARS scientists in Mayaguez, Puerto Rico demonstrated the following: 1) Fusarium spp. cause CFR in Puerto Rico; 2) the coffee berry borer (CBB) has Fusarium spp. as part of its microbiota; 3) this insect is responsible for spreading Fusarium spp. In coffee fields. A total of nine Fusarium species in six Fusarium species complexes were identified and collected from CBBs and from rotten coffee fruits in the field. Pathogenicity tests showed that five Fusarium species (F. bostrycoides, F. lateritium, F. nirenbergiae, F. solani-melongenae and F. pseudocircinatum) were pathogens of coffee causing CFR on green coffee 15 days after inoculation. Internal rot was significantly higher than external rot indicating that these pathogens use the hole left by the CBB to penetrate and infect coffee tissue. Fusarium bostrycoides was the most predominant species isolated from the CBB microbiota, coffee fruits with symptoms of CFR and from isolates recovered from pathogenicity tests suggesting a possible symbiosis between F. bostrycoides and the CBB. To our knowledge, this is the first report of F. botryscoides, F. solani melongenae, F. pseudocircinatum and F. nirenbergiae causing CFR worldwide and the first report of F. lateritium causing CFR in Puerto Rico. Fusarium species can produce mycotoxins and may cause diseases in plants. Understanding that CFR is a disease complex that includes Fusarium species and how the CBB is contributing to disperse these fungi in coffee farms is important to address the best management practices of this disease in Puerto Rico and other coffee-producing countries worldwide.
4. The Sigatoka Disease Complex Caused by Pseudocercospora spp. and Other Fungal Pathogens Associated with Musa spp. in Puerto Rico. Bananas and plantains (Musa spp.) production worldwide is being limited by fungal diseases. The identification and characterization of these fungi is imperative for the establishment of specific management approaches. Therefore, sixty-one leaf samples of Musa spp. showing fungi diseases symptoms were collected throughout different regions of Puerto Rico by ARS scientists and University of Puerto Rico scientists for diagnosis analysis. Molecular and morphological characterization found that Black Sigatoka, caused by Pseudocercospora fijiensis, is the most frequent disease. However, other fungi such as Cladosporium spp., Corynespora spp., Neocordana spp., Zasmidium spp., and Zygophiala spp. were also found in lower frequency. The identification of these fungal pathogens associated with Musa spp. provides basic information to establish quarantine regulations and an effective and specific management approach for its control in Puerto Rico.
Review Publications
Aviles-Noriega, A., Serrato Diaz, L.M., Giraldo-Zapata, M.C., Cuevas, H.E., Rivera-Vargas, L.I. 2024. The Sigatoka disease complex caused by Pseudocercospora spp. and other fungal pathogens associated with Musa spp. in Puerto Rico. Plant Disease. https://doi.org/10.1094/PDIS-03-23-0433-RE.
Carrasquillo, M.Y., Mariño, Y.A., Medina, A.G., Serrato Diaz, L.M., Bayman, P. 2023. Coffee fruit rot in Puerto Rico: distribution, ecology and associated fungi. European Journal of Plant Pathology. 168: 527-540. https://doi.org/10.1007/s10658-023-02781-1.
Serrato Diaz, L.M., Simbaña-Carrera, L., Velez-Negron, Y., Rivera-Vargas, L.I. 2023. Detection and incidence of pineapple heart rot disease caused by Phytophthora nicotianae in commercial farms in Puerto Rico. Journal of Agriculture of the University of Puerto Rico. 106(2):233-246. https://doi.org/10.46429/jaupr.v106i2.21155.
Goenaga, R.J., Marrero Soto, A.R. 2024. Yield and fruit quality traits of rambutan cultivars grafted onto three rootstocks and grown in a Mollisol soil in Puerto Rico. Journal of Agriculture of the University of Puerto Rico. 108(1):1-11. https://doi.org/10.46429/jaupr.v108i1.21409.
Serrato Diaz, L.M., Mariño-Cardenas, Y.A., Gonzalez De Jesus, J., Goenaga, R.J., Bayman, P. 2024. Coffee fruit rot: the previously unrecognized role of fusarium and its interactions with the coffee berry borer (Hypothenemus hampei). Phytopathology. https://doi.org/10.1094/PHYTO-02-24-0046-R.