Identification of Bacterial Wilt (Erwinia tracheiphila) Resistances in USDA Melon Collection.

Bimala Acharya,C Korsi Dumenyo,Yiqun Weng,Ali Taheri,Lucas Mackasmiel,Christine A Ondzighi-Assoume

doi:10.3390/plants10091972

Bimala Acharya, C Korsi Dumenyo + Show 4 more

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https://doi.org/10.3390/plants10091972

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Abstract

Bacterial wilt (BW) caused by the Gram-negative bacterium, Erwinia tracheiphila (Et.), is an important disease in melon (Cucumis melo L.). BW-resistant commercial melon varieties are not widely available. There are also no effective pathogen-based disease management strategies as BW-infected plants ultimately die. The purpose of this study is to identify BW-resistant melon accessions in the United States Department of Agriculture (USDA) collection. We tested 118 melon accessions in two inoculation trials under controlled environments. Four-week-old seedlings of test materials were mechanically inoculated with the fluorescently (GFP) labeled or unlabeled E. tracheiphila strain, Hca1-5N. We recorded the number of days to wilting of inoculated leaf (DWIL), days to wilting of whole plant (DWWP) and days to death of the plant (DDP). We identified four melon lines with high resistance to BW inoculation based on all three parameters. Fluorescent microscopy was used to visualize the host colonization dynamics of labeled bacteria from the point of inoculation into petioles, stem and roots in resistant and susceptible melon accessions, which provides an insight into possible mechanisms of BW resistance in melon. The resistant melon lines identified from this study could be valuable resistance sources for breeding of BW resistance as well as the study of cucurbit—E. tracheiphila interactions.

Highlights

Cucurbit crops, belonging to the family Cucurbitaceae, are grown widely in both tropical and subtropical regions of the world [1,2]
The screenings were performed in two greenhouse experiments conducted in summer 2019 (EXPT1) and autumn 2019 (EXPT2), respectively
Data were recorded for days to wilting of the inoculated leaf (DWIL), days to wilting of the whole plant (DWWP) and days to death of the plant (DDP)

Summary

Introduction

Cucurbit crops, belonging to the family Cucurbitaceae, are grown widely in both tropical and subtropical regions of the world [1,2]. The Cucurbitaceae family comprises 96 genera and about 1000 species, out of which 33 are cultivated species including major cucurbits such as cucumber (Cucumis sativus L.), melon (Cucumis melo L.), watermelon (Citrullus lanatus Thunb.) and pumpkin/squash Cucurbits are grown mostly as fruits and vegetables for human nutrition. Some cucurbits are consumed raw as desserts (watermelon, muskmelon) and salad (cucumber and long melons), while some others are cooked as vegetables (bottle gourd, bitter gourd, sponge gourd, ridge gourd, summer squash, squash melon, pumpkin, etc.). After post-harvest processing, some cucurbits such as cucumber and pointed gourd are used as pickles, while pumpkin and ash gourd are used in jam and candy industries, respectively [4]. In the United States, melons are cultivated on approximately 300,000 acres annually with equivalent to over two million tons annual output from 2017 to 2020 [5]

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