First Report of Postharvest Stem End Rot Disease on MD2 Pineapple Fruits Caused by Neoscytalidium dimidiatum in Malaysia

Abstract

Repeated sampling conducted from December 2019 to March 2020, and fruit of pineapple (Ananas comosus) var MD2 showing early stem end rot symptoms including brown and rotten fruit skin near the stem end region (Fig.1Aa) or darker skin with black discoloration (Fig.1Ab) indicated a consistent fungal infection. The samples (30 fruits from each location) were collected from store houses in three farmer fields with 60% disease incidence in Serdang, (3.0220oN,101.7055oE), Selangor, West Malaysia. The pulp of infected fruits appeared watery with characteristic spoilage odour. Symptomatic necrotic tissues from stem end region and skin were cut in to pieces (1x1cm), surface sterilized and plated onto potato dextrose agar amended aseptically with 0.5 g L-1 streptomycin sulphate. The plates were incubated at room temperature (28±2oC) in natural light conditions. Five days old cultures were light grey in colour and gradually turned dark brown to black with dense deeply tufted, mycelium as the culture aged (Fig.1B, C). Conidial morphology was observed using compound microscope (Olympus model BX-50F4, Tokyo, Japan) equipped with Dino-Eye. Branched mycelia with 0-1 septate arthospores were evident in 14 days old cultures (Fig.1D). Measured arthroconidia (5 to10x3 to 4.5µm) were ellipsoid to ovoid or round shaped, hyaline with an acutely rounded apex, truncate base, initially aseptate (Fig.1E) and arranged as chain at maturity (Fig.1F). The pathogen was identified through PCR amplification of the internal transcribed spacer (ITS) region using ITS1 and ITS4 primers (White et al., 1990) and BLASTn homology search as Neoscytalidium dimidiatum based on 100% similarity to a reference sequence (accession number KJ648577) that was previously deposited (Mohd et al.,2013). The sequence was deposited in Gen Bank ( accession number MW082810). Pathogenicity test was performed using the mycelial plug inoculation method and repeated twice with five replicates. Healthy MD2 pineapple fruits were surface sterilized with 1% NaOCl solution for15 min. followed by washing with sterilized distilled water. One centimeter diameter PDA plug at the margin of actively growing seven days old cultures were inserted in each of two inoculation wounds made on the skin and stem end of each fruit then the wounds were wrapped with moist cotton wool. Non-colonized PDA plugs were used to inoculate the control fruits. Fruits were incubated under 85% RH at room temperature. Five days after inoculation, the fruits showed similar dark necrotic discoloration and confirmed as N.dimidiatum by PCR (Fig.1G). The Koch postulates were fulfilled by inoculation and re-isolation of the fungal pathogen. This pathogen has also been reported previously to cause economic losses on a number of other hosts, such as pitayah fruits in Israel and Malaysia (Erza et al., 2013; Mohd et al., 2013)) and almond in California (Mohomed et al., 2018). To our knowledge this is the first report of N. dimidiatum causing postharvest stem end rot on MD2 pineapple in Malaysia. It may have the possibility to develop postharvest economic losses to pineapple industry, if severely affected fruits with high population of the pathogen left unattended in store houses.

Pest categorisation of Neoscytalidium dimidiatum

“… Fabaceae Acacias Chandra ( 1974 ) Albizia lebbeck Fabaceae Siris tree Elshafie and Ba‐Omar ( 2002 ) Agave sp. Asparagaceae Kranz ( 1963 ) Agave sisalana Asparagaceae Sisal Xie et al ( 2021 ) Anacardium occidentale Anacardiaceae Cashew Coutinho et al ( 2018 ) Ananas comosus Bromeliaceae Pineapple Kuruppu et al ( 2021 ) Arachnis sp. Orchidaceae Scorpion orchid Williams and Liu ( 1976 ) Araucaria sp.…”

Supplementary 4

“…These fungal pathogens are considered important as they do not only attack leaves but also other pineapple plant parts such as butt (C. paradoxa) and fruits (Fusarium spp.). Recently, Kuruppu et al (2020) reported that the fungus Neoscytalidium dimidiatum can cause stem-end rot of pineapple particularly on pineapple MD2 variety in Malaysia. In our research (unpublished data), this fungal pathogen can also cause brown leaf spot disease on pineapple leaf and fruitlet rot on pineapple fruit (Figure 1).…”

“…Normally, the colour of the infected area turns cream or almost white, but the margins of the spot often remain brown (Figure 1). This fungal pathogen also causes stem-end rot disease and the disease symptoms have been explained by Kuruppu et al (2020) as brown and rotten fruit skin near the stem end region or darker skin with black discolouration.…”

A review of research trends on Nattrassia mangiferae from 1966-2022: A bibliometric approach

“…The distribution of this genus has extended to all continents. Neoscytalidium genus can influence the different parts of plants by causing diseases that show various symptoms on aerial and underground parts of hosts, including shoot blight canker and gummosis (Polizzi et al, 2009), dieback (Ray et al, 2010), collar and root rot (Machado et al, 2012), brown spot (Lan et al, 2012), death of graft (Chen et al, 2013), internal black rot (Ezea et al, 2013), shoot and needle blight (Türkölmez et al, 2019a), tuber rot (Derviş et al, 2020a), root and stem rot (Oksal and Ozer, 2021;Kuruppu et al, 2021), stem-end rot (Li et al, 2021), sooty canker (Yeganeh and Mohammadi, 2022), and leaf scorch (Table 1). Members in the genus Neoscytalidium have been reported as pathogenic agents on various crops and trees, such as almond (Prunus dulcis), Avicennia marina Forssk., baobab (Adansonia gibbosa), bardi bush (Acacia synchronica), blue grevillea (Grevillia agrifolia), rattlepod (Crotalaria medicaginea), olive (Olea europaea L.), etc.…”

“…Members in the genus Neoscytalidium have been reported as pathogenic agents on various crops and trees, such as almond (Prunus dulcis), Avicennia marina Forssk., baobab (Adansonia gibbosa), bardi bush (Acacia synchronica), blue grevillea (Grevillia agrifolia), rattlepod (Crotalaria medicaginea), olive (Olea europaea L.), etc. (Table 1), causing economic yield losses (Pavlic et al, 2008;Ray et al, 2010;Sakalidis et al, 2011;Rahmani, 2018;Chakusary et al, 2019;Sabernasab et al, 2019;Derviş et al, 2019;Mello et al, 2019;Türkölmez et al, 2019;Brito et al, 2020;Alananbeh et al, 2020;Oksal and Ozer, 2021;Kuruppu et al, 2021;Oren et al, 2022;Yeganeh and Mohammadi, 2022;. Though, they have also been reported as opportunistic human pathogens causing chronic superficial infections of skin, nails, and nose, cutaneous, invasive cutaneous, deep cutaneous infection, onychomycosis, dermatomycosis, fingernail onychomycosis, superficial black onychomycosis, rhinosinusitis, brain abscess, and pulmonary disease (Bakhshizadeh et al, 2014;Dionne et al, 2015;Yang et al, 2019;Jo et al, 2020;González Cortés et al, 2021;Raiesi et al, 2022).…”