First Report of Pestalotiopsis microspora Causing Leaf Blight of Banana in Bangladesh

Abstract

Banana (Musa sp.) is one of the most important fruit crops in the world. It is also a very popular fruit crop and cultivated widely in Bangladesh. Banana diseases are one of the limiting factors for its production. Recently, a new banana leaf blight was detected in various districts of Gazipur, Bangladesh, with an incidence of 5 to 10% in June 2020 and 15 to 20% in January 2021. The initial symptoms of the disease were narrow dark brown lesions (2 to 5 x 5 to 12 mm) that later became irregular brown spots (10 to 15 x 5 to 7 mm). The lesions gradually spread from the middle of the leaf to the margin and dark brown spots appeared on the diseased leaves. There was a clear golden yellowish boundary around the spot. Blighted tissue often covered one-thirds to one-half of the infected leaves. To isolate the pathogen, 100 diseased leaves were collected from five different locations in Gazipur, Bangladesh. Small pieces (5x5 mm) were cut from the margins of lesions and surface sterilized with 75% ethanol for 30 s followed by 1% NaClO for 1 min. The samples were then rinsed three times with sterile distilled water, dried on sterilized filter paper, and placed on 1% water agar at 25°C for 7 days. Hyphal tips were then excised, placed on PDA and incubated at 25°C for 7 days. From the 20 isolates obtained, the colony characteristics and conidial morphology of three isolates, BLS_BU1, BLS_BU2, and BLS_BU3, were examined. The colony of all of three isolates was white, cottony, and circular in growth. The acervuli were black and covered all the culture plate. Conidia of all the isolates were 5-celled, fusiform, and wider in the middle than the apical and basal cells. The three internal cells were olivaceous, concolourous, and slightly constricted at the septae; the terminal cells were hyaline (Shi et al. 2015). The conidium measured 20.3 ± 1.2 to 22.7 ± 1.8 by 7.2 ± 0.6 to 8.6 ± 0.4 μm. The mean lengths of the two to four hyaline apical appendages were 20.5 to 30.25 μm and the hyaline basal appendage was 6.1 to 7.6 μm (Han et al. 2019). DNA was extracted from the fungal colony using a DNeasy Plant Mini Kit (Qiagen). PCR was performed with primers ITS1/ITS4 ITS region and Sanger sequenced by Macrogen (Seoul, Korea) (White et al. 1990). Isolates BLS_BU1 (MH707065), BLS_BU2 (MH707065), and BLS_BU3 (MH712283) had a sequence similarity of over 99% with GenBank reference Pestalotiopsis microspora (MH707065) of National Center for Biotechnology Information (NCBI) database. The reconstructed phylogenetic tree also confirmed their phylogenetic position. To assess pathogenicity, the leaves of four 2-month-old healthy plants were needle wounded and inoculated with a spore suspension (106 spores/ ml) harvested from 10-day-old cultures of isolate BLS_BU1. As a control treatment, five leaves of two healthy plants were inoculated with sterile distilled water. Treated plants were maintained in the field with average temperature ranging from 28°C to 30°C and relative humidity from 75% to 80%. After 2 weeks, all inoculated leaves produced characteristic symptoms similar to those observed in the field. However, the control plants did not develop any symptoms. Pestalotiopsis microspora from the inoculated leaves was successfully reisolated, thus confirmed that P. microspora was the cause of leaf blight of banana. To our knowledge, banana appears to be a new host of P. microspora. this This is the first report of leaf blight of banana caused by P. microspora in Bangladesh.

Pestalotiopsis microspora causes leaf spot on Adenium obesum

“…The characteristics exhibited by the colonies of the RD1, RD3 and RD7 isolates in PDA were white mycelia with hyaline hyphae, branched septa, radial growth, cottony and formation of dark masses containing the reproductive structures of the pathogen. These colony characteristics are similar to those described by several studies concerning colonies of P. microspora isolates (Jeon et al., 2006; Wu et al., 2009; Shen et al., 2014; Jeon and Cheon, 2014; Bhuiyan et al., 2021). The conidia, on the contrary, were fusiform and euseptados with had two hyaline cells (apical and basal) and three dark‐coloured fusiform median cells.…”

“…The size of the conidia ranged from 15.03 to 34.28 µm in length by 3.55 to 6.27 µm in width, with one to three apical appendages from 2.24 to 26.44 µm in length and a basal appendage measuring 1.51-8.02 µm in length. The morphological characteristics of the conidia of the RD1, RD3 and RD7 fungal isolates were similar to those described in the literature for the genus Pestalotiopsis (Griffiths & Swart, 1974;Jeewon et al, 2002;Sutton, 1980), and those described by several studies when describing the species P. microspora (Bhuiyan et al, 2021;Jeon et al, 2006;Shen et al, 2014;Wu et al, 2009).…”

Pest categorisation of Pestalotiopsis microspora

“…Using the above criteria, the Panel identified the following plant species (crops and ornamentals) as main hosts of P. microspora relevant for the EU: Actinidia chinensis (Li et al., 2016 ), Ampelopsis grossedentata (Yuan et al., 2022 ), Eriobotrya japonica (Lu et al., 2016 ), Musa spp. (Bhuiyan et al., 2022 ), Persea americana (Kimaru et al., 2018 ), Psidium guajava (El‐Argawy, 2015 ) and Vaccinium corymbosum (Yi‐Lan et al., 2021 ).…”

“…Pestalotiopsis microspora can cause symptoms on several parts of its host plants. However, it affects mainly the leaves, causing leaf spot (De Jesus et al., 2022 ; Herliyana et al., 2022 ; Shen et al., 2014 ; Yuan et al., 2022 ) and leaf blight (Bhuiyan et al., 2022 ; Herliyana et al., 2022 ; Jeon et al., 2007 ; Jeon & Cheon, 2014 ; Ngobisa et al., 2018 ; Wu et al., 2009 ; Xiao et al., 2016 ; Zhong Jiu et al., 2010 ). It can affect roots, causing root rot (Lu et al., 2016 ), but also fruits, causing fruit spots (Chuanqing et al., 2010 ; Shi et al., 2015 ), scabby fruit canker (Keith et al., 2006 ) and pre‐ (Sultana et al., 2021 ) and post‐harvest fruit rot (Chen, Chen, et al., 2016 ; Li et al., 2016 ), and to a lesser extent twigs, causing twig blight (Ren et al., 2021 ).…”

“…The molecular techniques available for the identification of P. microspora are mostly based on the sequencing of the internal transcribed spacers (ITS) of genomic rDNA, in particular the region ITS1–5.8S–ITS2 (Bhuiyan et al., 2022 ; De Jesus et al., 2022 ; Herliyana et al., 2022 ; Jeon et al., 2007 ; Jeon & Cheon, 2014 ; Lu et al., 2016 ; Shi et al., 2015 ; Xiao et al., 2016 ; Zhong Jiu et al., 2010 ). Other DNA regions, such as the protein‐coding gene beta‐tubulin ( tub2 ), have been used together with the ITS for a more reliable identification of P. microspora (Li et al., 2016 ; Yuan et al., 2022 ).…”