Epidemiological study ofCucumber green mottle mosaic virusin greenhouses enables reduction of disease damage in cucurbit production

Abstract

Since 2007, the tobamovirus Cucumber green mottle mosaic virus (CGMMV) has become widespread in Israel, causing severe damage to trellised cucumber and melon in greenhouses and watermelon grown in open fields. To reduce disease damage below the economic threshold, this study focused on four objectives: (a) monitoring the patterns of virus distribution within commercial cucumber greenhouses; (b) studying the potential transmission of CGMMV by agrotechnical activities; (c) virus localization in plant tissues; and (d) searching for techniques that might be adapted for mitigating the disease in trellised cucurbit growth. The results of our surveys demonstrated the role of contaminated seeds and soil as primary inoculum sources, and secondary spread caused by agrotechnical activities. The patterns of secondary disease spread were demonstrated in a series of inoculation experiments involving contaminated knives, shears or hands on wet and dry plants, conducted under research-greenhouse conditions. In parallel experiments using CGMMV-specific antibody and secondary antibody conjugated to Alexa fluor 488, the viral coat protein was visualized in several plant tissues: phloem, xylem, trichomes and grasping tendrils. In addition, commercial-greenhouse experiments were aimed at reducing the number of inoculum sources by identifying and removing infected plants from the plots (early monitoring) prior to agrotechnical activities and/or by adding intermediate medium (IM), such as virus-free compost, to the planting pits at the planting stage. It is suggested that the use of IM combined with early monitoring, awareness of worker mobility (from contaminated structures to young planting areas) and proper sanitation (e.g. disinfection of agrotechnical tools) may reduce the yield losses caused by CGMMV below the economic threshold. of the RNA strand from degradation (Ono et al., 1972;Ugaki et al., 1991;Tan et al., 2000). Tobamoviruses are known to cause severe crop diseases and are responsible for significant economic losses worldwide in a wide range of plant species (e.g. Cucurbitaceae and Solanaceae). The symptoms induced by tobamoviruses include mottling and mosaic on leaves, as well as different degrees of fruit mottling or distortion (Fig. 1), which result in severe yield losses in pepper (Capsicum annum), tomato (Solanum Ann Appl Biol 168 (2016) 29-40 29 © 2015 Association of Applied Biologists Reducing CGMMV damage in greenhouses V. Reingold et al.

A New Israeli Tobamovirus Isolate Infects Tomato Plants Harboring Tm-22 Resistance Genes

“…Growing trellised tomato plants inside protected structures (glasshouses, greenhouses and net-houses) has allowed control of entry of virus-transmitting insects. On the other hand, cultivation in protected structures exposes the plants to mechanically transmitted tobamoviruses due to intensive agro-techniques [6, 33, 34]. For decades, cultivating tomatoes in protected structures was achieved via the genotypes of the elite tomato varieties harboring the resistance genes Tm-1 , Tm-2 and Tm-2 2 [8].…”

Control of Cucumber green mottle mosaic virus in commercial greenhouse production with agricultural disinfectants and resistant cucumber varieties

“…CGMMV posts a serious threat to greenhouse cucumber, as well as other cucurbit crop productions worldwide. This virus is capable of rapidly spreading throughout a greenhouse or other protected cultivations, destroying crops and resulting in significant economic losses to growers (Reingold et al, 2016). CGMMV can also persist in the environment, infecting new crops and perpetuating the disease cycle.…”

“…This property of stability, combined with its high infectivity rate through mechanical contact with the foliage, and capacity to affect subsequent greenhouse crops, have increased the economic importance of this virus. High CGMMV infections may force growers to terminate their crops early because of unproductiveness, hence reducing the overall profitability of their operations (Fletcher et al, 1969;Reingold et al, 2016).…”

First Complete Genome Sequence of Cucumber green mottle mosaic virus Isolated from Australia

“…The main hosts are crop species belonging to the Cucurbitaceae, in which it causes symptoms of leaf mottling and mosaic on foliage, plant dwarfing, flesh discoloration, surface mottling, and distortion of fruit (7). Fruit yield and quality losses can be severe in some cucurbit crop species, including watermelon and cucumber (Cucumis sativus) (8, 9). CGMMV is seed-borne, highly contact transmissible, and survives for years in plant debris and soil.…”

“…CGMMV is seed-borne, highly contact transmissible, and survives for years in plant debris and soil. It has no known insect vector, but pollination by bees is suspected to play a role in its plant-to-plant spread (9). CGMMV gets introduced to new cucurbit-growing regions by planting infected seed or seedlings (7).…”