Botryosphaeriaceae as causal agents of Dieback and Corky Bark in Rambutan and Longan

Authors: SERRATO-DIAZ, L. - University Of Puerto Rico; AVILES-NORIEGA, A. - University Of Puerto Rico; SOTO-BAUZO, A. - University Of Puerto Rico; RIVERA-VARGAS, L. - University Of Puerto Rico; Goenaga, Ricardo; BAYMAN, P. - University Of Puerto Rico

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2019
Publication Date: 10/28/2019
Citation: Serrato-Diaz, L.M., Aviles-Noriega, A., Soto-Bauzo, A., Rivera-Vargas, L., Goenaga, R.J., Bayman, P. 2019. Botryosphaeriaceae as causal agents of Dieback and Corky Bark in Rambutan and Longan. Plant Disease. 104:105-115.

Interpretive Summary: Fungi in the Botryosphaeriaceae family cause dieback, fruit rots and stem cankers in many tropical fruit trees. To identify which Botryosphaeriaceae were present in tropical fruits in Puerto Rico and if they could cause dieback in rambutan and longan, a disease survey was conducted throughout the island from 2008 to 2016. This study confirms that a variety of fungi species in the Botryosphaeriaceae can cause vascular necrosis followed by dieback in rambutan and longan in Puerto Rico. It also shows that these fungi can be pathogenic in adjacent orchards of different fruit tree species, suggesting that mixed plantings will not reduce disease. This study also provide evidence that corky bark symptoms in rambutan and longan can be caused by pathogens in the Botryosphaeriaceae family. Pathogenicity studies need to be conducted to determine if D. nepheliae, previously associated to cause corky bark symptoms, can also cause corky bark on rambutan and longan, or if it is a saprotroph or secondary pathogen feeding on dead organic material left by infections caused by Botryosphaeriaceae. Cross-inoculation with Lasiodiplodia and Neofusicoccum isolates from different hosts showed that pathogenicity is wide-spectrum. These adaptations to different environments and hosts by Botryosphaeriaceae indicate that different planting alternatives should be considered for better crop management.

Technical Abstract: Fungi in the Botryosphaeriaceae cause dieback, fruit rots and stem cankers in many tropical fruit trees. To identify which Botryosphaeriaceae were present in tropical fruits in Puerto Rico and if they could cause dieback in rambutan and longan, a disease survey was conducted throughout the island from 2008 to 2016. Diseased organs of rambutan, longan, mango, and tangerine showing different symptoms were collected and 39 isolates in the Botryosphaeriaceae were isolated and identified. Phylogenetic analysis of three nuclear genes identified nine species, three Neofusicoccum spp. and six Lasiodiplodia spp. All 39 isolates were inoculated on healthy 1-year-old rambutan and longan saplings to confirm pathogenicity. Dieback on both rambutan and longan was observed at 14 days after inoculation (DAI). 14 isolates in seven species (Neofusicoccum parvum, N. batangarum, L. pseudotheobromae, L. theobromae, L. hormozganensis, L. brasiliense and L. iraniensis) caused dieback in rambutan. Five of the pathogenic isolates were collected from rambutan, four from longan, two from mango and three from tangerine. Ten isolates of four Lasiodiplodia spp caused dieback in longan: L. pseudotheobromae, L. theobromae, L. hormozganensis and L. iraniensis. Of these, three were collected from rambutan, three from longan, one from mango and three from tangerine. Pycnidia on branches, called corky bark symptoms, were observed on both rambutan and longan at 60 DAI. These cross-inoculations showed that pathogenicity is wide in spectrum, indicating that different planting alternatives should be considered for better crop management.