Purpose: Stem-end rot (SER) is an endophytic fungal infection of avocado causing significant postharvest losses, affecting its marketability. This study was conducted to identify effective concentrations of selected eco-friendly essential oils and chemicals to control SER pathogens by conducting in vitro bioassays and to develop treatments to control SER in naturally infected avocado (cv. Pollock) using less hazardous alternatives to synthetic fungicides. Research Method:In vitro disc volatilization and poison food bioassays were conducted to identify inhibitory concentrations of some essential oils and chemicals against SER pathogens. Avocado fruits were subjected to eco-friendly fumigation and dip treatments and their pathological, physicochemical and sensory properties were assessed after 7 days of storage at 15 °C. Findings: Disc volatilization bioassay revealed that 5 µL/plate clove oil was most effective againstLasiodiplodia theobromae, Diaporthe nelumbonis and Fusarium oxysporum. According to Poisoned food bioassay, 5% (w/v) sodium bicarbonate and 0.07% (v/v) acetic acid were highly effective against the test pathogens. SER incidence of avocado fruits has been successfully delayed for 7 days after subjecting to fumigation treatment with clove oil and dip treatments with sodium bicarbonate and acetic acid, followed by storage at 15 °C. None of the treatments adversely affected physicochemical and sensory properties of avocado.Originality/Value: Treatments could be further improved by conducting a medium-scale in vivo trial to obtain good quality avocado with higher consumer acceptance.

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.

Purpose : Mango (Mangifera indica L. cv. Tom EJC) has a high economic value due to its unique qualities. Postharvest diseases such as anthracnose cause considerable loss of fruits in the market. Applications of synthetic fungicides are the common practice for controlling postharvest diseases, which could lead to hazardous effects on health. Therefore, search for alternative measures for the control of anthracnose are in demand. Research Method : Different fungal species have been described as causative agents of above disease. To determine the causative agent, fungal isolations were done from symptomatic fruits and identified by morphological and molecular techniques. Sodium bicarbonate, and sodium metabisulphite were used as GRAS (Generally Recognized as Safe) compounds and clove, cinnamon and citronella oils were used as essential oils during in-vitro studies to evaluate their potential to control the pathogen. The mycelial inhibitory capacity of five concentrations (1µLplate-1-5µLplate-1) of each essential oil was evaluated in-vitro disc volatilization method. Compounds with minimum inhibitory concentrations were selected for in-vivo studies. Essential oil treatments for mango comprised of fumigation and application of GRAS compounds by dipping 15 and 30 minute time intervals. Physiochemical properties (pH, titrable acidity and total soluble solid content) of treated and non-treated mango fruits were evaluated. Findings : The identified causative agent of anthracnose was Colletotrichum siamense. Sodium bicarbonate (80000ppm), sodium metabisulphite (1500ppm) showed 100% inhibition of radial mycelia growth against the pathogen through in-vitro poison food method.100% inhibition of radial mycelia growth was reported with clove and cinnamon oil at all the concentrations tested (1-5µLplate-1). The citronella oil showed the lowest inhibitory activity. 15 minute and 30 minute dipping in sodium bicarbonate and fumigation with clove oil and cinnamon oil treatments effectively controlled anthracnose disease in mango, in comparison to the recommended fungicide Chlorothalonil (3mL/L). Physiochemical properties of mango were not altered by any of the treatments in comparison to no-treated fruits. Originality / Value : These results suggest that Sodium bicarbonate, Clove oil and Cinnamon oil could be used as alternatives to control the anthracnose disease in mango.

Avocado (Persia americana) is one of the most popular fruits grown in Sri Lanka. Postharvest infections occur wherever the crops are cultivated. Among them, stem-end rot (SER) is the major disease reported. Several fungal species including Lasiodiplodia and Dothiorella spp. have been reported to be associated with this disease in regions where avocado is grown. The aims of this research were to identify the fungal pathogens associated with the stem-end rot of avocado in Sri Lanka based on morphological characteristics in combination with molecular and phylogenetic analysis. Diseased avocado fruits were collected from local markets and causal agents were isolated. Colony morphology and characteristics of conidia were observed using phase-contrast microscopy. Sequence analysis was performed using internal transcribed spacers (ITS) of the ribosomal DNA followed by phylogenetic analysis. Four endophytic fungal isolates were identified and designated as SER 01, SER 02, SER 03 and SER 04 which were distinguished respectively as Lasiodiplodia theobromae, Lasiodiplodia hormozganensis, Diaporthe nelumbonis and Fusarium oxysporum. To our knowledge, this is the first evidence on the occurrence of L. hormozganensis, D. nelumbonis and F. oxysporum associated with SER of avocado in Sri Lanka. Identified pathogens were proven to be collectively pathogenic to avocado following demonstration of Koch's postulates. The average value of collective disease severity after seven days of inoculation of avocado cv. Pollock was 40% at 28 C and it always fluctuated between 30% and 45%.