Cacao Phytophthora Pod Rot: Symptoms & Pathogenicity | InformativeBD

Angelina T. Gonzales, Diosa G. Alasaas, and  Macluven T. Gonzales from the different institute of the Philippines. wrote a research article about, Cacao Phytophthora Pod Rot: Symptoms & Pathogenicity, entitled,  "Symptomatology and pathogenicity of Phytophthora pod rot disease associated with Cacao plants in selected municipalities in the Province of Cagayan, Philippines". This research paper published by the Journal of Biodiversity and Environmental Sciences | JBES. an open access scholarly research journal on Biodiversity under the affiliation of the International Network For Natural Sciences | INNSpub. an open access multidisciplinary research journal publisher.

Abstract

The study aimed to describe the Phytophtora pod rot (PPR) symptoms disease associatedwith cacao plants and its pathogenicity to cacao. Specifically, it aimed to: (a) describe the PPR disease symptoms associated with cacao plants; (b) determine the pathogenicity of PPR disease to cacao seedlings, cacao flower and unripe and ripe pods; (c) document the reaction of cacao varieties to PPR disease. Samples isolated from infected cacao pods of five cacao farms revealed 14 isolates of Phythophthora spp. Pathogenicity test showed development of typical symptoms of Phythophthora of isolates from infected tissue of cacao pod. Incubation period was recorded between 4 days to 14 days after inoculation. The pathogen associated with Phythophthora pod rot belongs to Phythophthora palmivora. Cacao seedlings from 21-days old to 6 months manifested water-soaking leaves to leaf blighting symptoms, while infected flowers were found to have blighting and necrotic symptoms. Ripe variety could easily infected compared to unripe pod as shown by oily brown appearance and it changes from brown to black. White leathery structure or whitish appearance (sporangia) on the surface of the pods and mummified pods in advance stages.

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Introduction

Cagayan valley region contributes 4% of the national cacao production from the 10% shared of Luzon and Visayas region outside of Mindanao which is 80% of the total production of the country. In Cagayan province, there are more than 73 cacao farmers growing cacao with cacao production areas ranging from 1-15 has. Cacao nurseries are also operational in the region. Cacao Nurseries and farms are located in Santa Praxedes, Sanchez Mira, Gonzaga, Lal-lo, Lasam, Gatarran and Penablanca (Fig. 1.). Visits of these cacao-producing towns and nurseries, it has been observed that a number of the cacao plants of various stages of growth show various deviations from normal and symptoms: i.e., seedling blight that starts with vein clearing on the younger and defoliation in older leaves of up to to 4 months old in polybags; flowers turned brown; in fruits, chocolate brown necrotic lesions is commonly observed on infected pods which usually are accompanied by seed rot are common in cacao pods. 

Then pathogen appears on the surface of the pod as a whitish down on which masses of sporangia are produced. Diseased cacao fruits are commonly observed in the municipality of Lasam and Gattaran, Cagayan, Philippines. 

To date, there are four most common cacao pests and diseases in the Philippines, i.e., black pod rot, vascular streak dieback, cacao borer, Helopeltis and cacao stem borer (Department of Agriculture Bureau of Agricultural Research as cited by Tan et al., 2016). Phytophthora pod rot is a major disease of cacao and causes 20 to 30% pod losses, and kills up to 10% of trees annually through stem cankers (Bowers, J. H, et al 2001; Guest, 2007, and Adomako, 2007). The disease was first reported as cacao canker in Java in 1924 (Hartley and Rands, 1924).

Phytophthora pod rot is caused by four different species in the Stramenopile genus Phytophthora: P. capsici, P. citrophthora, P. megakarya, and P. palmivora which occur in almost all cacao growing region in the world (Guest, 2007). P. megakarya, which is restricted to Africa is the most aggressive species, causing 60-100% yield loss compared to the 15-30% losses attributed to P. palmivora (Nyassé et al., 2002; Tahi et al., 2006). Eight species of Phytophthora have been isolated from cacao: P. palmivora (Butler) Butler, P. megakarya (Brasier and Griffin), P. capsici (Leonian emend.) (P. tropicalis), P. katsurae (Ko and Chang), P. citrophthora (R.E. Smith and E.H. Smith), P. arecae (Coleman) Pethybridge, P. nicotianae (van Breda de Haan) and P. megasperma (Dreschler) (Erwin and Ribeiro 1996; Iwaro et al. 1997; Appiah et al. 2003). 

In the Philippines, cacao had been attacked by disease caused by Phythopthora faberi (Reinking, 1918; Tangonan (1999) host index listed Phythopthora pod rot disease in cacao. In addition, a review of Solpot (2001) enumerated the following diseases of cacao. Similar symptoms or disorders were reported by Panguntalan et al., (2022) on cacao plants of an orchard in Calauan, Laguna.

However, no report is available if the disease is occurring in the cacao nurseries and cacao farms in the province of Cagayan. Thus, this study was conducted to validate if Phytophthora spp. is involved and caused cacao pod rot disease in the cacao farms in Cagayan. This study is undertaken to: (a) collect asymptomatic and symptomatic cacao parts; and (b) isolate, characterize and identify pathogen associated with seedlings, flower, stems, and young and mature pods; (c) and observe and document if the tentative PRR isolates incite PRR disease in seedlings, flowers, and young and matured cacao pods.

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 Source : Symptomatology and pathogenicity of Phytophthora pod rot disease associated with Cacao plants inselected municipalities in the Province of Cagayan, Philippines