# First Report of Agroathelia rolfsii Causing White Fruit Rot in Oil Palm Hybrid OxG in Colombia

## TL;DR

This study identifies Agroathelia rolfsii as the first reported cause of white fruit rot in oil palm hybrids in Colombia, affecting yields across multiple regions.

## Contribution

The first report of Agroathelia rolfsii causing white fruit rot in oil palm in Colombia.

## Key findings

- White fruit rot symptoms were observed in oil palm hybrids across three regions in Colombia.
- Agroathelia rolfsii was confirmed as the causal agent through morphological and molecular analysis and by fulfilling Koch’s postulates.
- Field and in vitro tests showed 100% incidence of infection by A. rolfsii isolates.

## Abstract

Colombia is the Latin American country with the second-largest area planted with OxG hybrid cultivars, covering more than 120,000 hectares Various health problems can affect yield, especially those affecting fruit. Since 2021, white fruit rot has been reported in the northern, central, and southwestern palm-growing areas. Therefore, the objective of this study is to identify associated symptoms and their causal agent. To this end, a total of six locations in the three palm-growing regions were visited, and 36 samples of affected fruits were collected to obtain microorganisms. These microorganisms were inoculated into detached fruits under in vitro conditions, and seven isolates were inoculated into bunches in the field. They were morphologically and molecularly characterized by partial sequencing of the ITS and TEF1 regions. Symptoms of white rot were observed, starting from the base of the fruit to the apex, with the development of a cottony mycelial mass, followed by the formation of sclerotia. A total of 33 organisms were obtained, 30 isolates identified as Agroathelia rolfsii, one Fusarium sp., one Rhizoctonia sp., and one Pestalotiopsis sp. isolate. The Agroathelia isolates exhibited white, cottony growth adhering to the surface of the PDA culture medium. After four days of growth, they developed globose to ellipsoid sclerotia (average 1.00 ± 0.26 (0.46–2.20 mm)). These were initially white and turned brown as they developed, with the average number of sclerotia per plate ranging from 4 to 449 (n = 6). In the in vitro pathogenicity test, only A. rolfsii isolates were pathogenic, with a 100% incidence, an average severity ranging from 10 to 40% infection, and a range of 10 to 100%. In field inoculations, 100% of the inoculated bunches exhibited symptoms similar to those observed under natural field conditions. In all cases, the pathogen was recovered, fulfilling Koch’s postulates and confirming that A. rolfsii is the causal agent of white fruit rot. This constitutes the first record of Agroathelia rolfsii in oil palm in Colombia.