Soybean green stem and foliar retention syndrome caused by Aphelenchoides besseyi

Abstract

Soybean, the most important agricultural product in Brazil, is widely cultivated all over the country. The occurrence of green stem and foliar retention (GSFR) has been reported since the beginning of the soybean cultivation in Brazil and its potential causes were attributed to severe attack of stinkbugs or plant nutritional disorders. About two decades ago, a new type of GSFR was reported in Brazilian tropical regions of soybean production, also of an unknown cause. Several possible causes were investigated, but the presence of the nematode Aphelenchoides sp. in symptomatic plants was frequently observed. Koch's postulates were conducted to check whether this nematode could be the cause of the syndrome. Specimens of Aphelenchoides sp. were isolated from soybean plants and multiplied in colonies of the fungus Fusarium sp. in PDA culture medium. Nematode suspensions were inoculated onto healthy soybean plants and the typical GSFR symptoms were observed. The nematode was recovered from the inoculated plants. Based on both morphological and molecular data, we suggest that Aphelenchoides besseyi is the causal agent of GSFR of soybeans in Brazil, a syndrome popularly known as "Soja Louca II".

Prevalence, damage, management and insecticide resistance of stink bug populations (Hemiptera: Pentatomidae) in commodity crops

“…In addition to these injuries, stink bug attack can cause foliar retention (Galileo & Heinrichs, 1978;Link & Storck, 1978), also known as delayed maturity, as well as green bean or green stem syndrome. However, this symptom is caused not only by stink bugs, but also by nutritional imbalance, drought during flowering and/or pod filling stages, excessive moisture during the maturation period and nematode infestations (Sosa-Gómez & Moscardi, 1995;Meyer et al, 2017).…”

Metabolomics of soybean green stem and foliar retention (GSFR) disease using mass spectrometry and molecular networking

“…genus comprises about 200 species. Some species can damage the aerial parts of the plants, affecting and extending the plant complete developmental cycle . The Aphelenchoides sp.…”

“…are mainly microphagous, and some feed exclusively on fungi. However, species such as Aphelenchoides besseyi , A. fragariae , A. ritzemabosi, and A. arachidis can parasitize plants, usually predating their air organs . Of those, A. besseyi is known to cause rice white tip, where flowers become sterile, and there is a reduction in production and in the size of grains .…”

A Rapid Diagnostic for Detection ofAphelenchoides besseyiandA. fujianensisBased on Real-Time PCR

“…Nevertheless, the frequent association of this nematode with forage grass seed represents a phytosanitary barrier for export to many countries where A. besseyi is listed as a quarantine pest (Marchi et al 2007). In addition, this species has been suggested as the causal agent of two new diseases: "black spot disease" on bean (Phaseolus vulgaris L.) in Costa Rica (Chaves et al 2013) and green stem and foliar retention in Brazil (Meyer et al 2017). This latter, popularly known as "mad soybean", is responsible for yield losses of up to 100% (Meyer et al 2017).…”

“…In addition, this species has been suggested as the causal agent of two new diseases: "black spot disease" on bean (Phaseolus vulgaris L.) in Costa Rica (Chaves et al 2013) and green stem and foliar retention in Brazil (Meyer et al 2017). This latter, popularly known as "mad soybean", is responsible for yield losses of up to 100% (Meyer et al 2017). Thus, it is imperative to ensure that appropriate phytosanitary measures and management strategies can be implemented against A. besseyi, and, therefore, rapid and reliable detection and identification tools are needed.…”