Diagnosis and management of halo blight in Australian mungbeans: a review

Abstract

Mungbean (Vigna radiata L. Wilczek var. radiata) is an important food crop cultivated on over 6 Mha throughout the world. Its short duration of 55–70 days, capacity to fix atmospheric nitrogen, and exceptional grain nutritional profile makes the crop a staple for smallholder and subsistence farmers. In Australia, mungbean is grown as a high-value export crop and established as a main summer rotation for dryland farmers. A major threat to the integrity of the industry is halo blight, a bacterial disease leading to necrotic lesions surrounded by a chlorotic halo that stunts and ultimately kills the plant. Caused by Pseudomonas savastanoi pv. phaseolicola, this seed-borne disease is extremely difficult to control, resulting in significant yield loss and production volatility. The challenge of managing halo blight is exacerbated by a wide host range that includes many legume and weed species, and the presence of multiple epidemiologically significant strains. Molecular technologies could play a pivotal role in addressing these issues. This review synthesises current and emerging technologies to develop improved management strategies for the control of halo blight in mungbean.

Characterisation of the Pseudomonas savastanoi pv. phaseolicola population found in Eastern Australia associated with halo blight disease in Vigna radiata

“…Known for over 90 years, halo blight disease of the Fabaceae family continues to threaten food production globally (Arnold et al 2011;Burkholder 1926;Noble et al 2019). However, limited research has explicitly focused on the interactions between the causal agent P. savastanoi pv.…”

“…Mungbean (Vigna radiata L. Wilczek var. radiata) is a grain legume that provides a vital source of nutrition for many countries and contributes significantly to Australian agricultural exports (Noble et al 2019;Shanmugasundaram et al 2009). Severely limiting the production of commercial mungbean crops in Australia is the seed-borne bacterial disease halo blight, caused by Pseudomonas savastanoi pv.…”

“…phaseolicola. An emerging threat in 1980, halo blight is now responsible for large-scale annual losses in mungbean crops and threatens the sustainability of the industry (Noble et al 2019). Knowledge of genetic variation within the pathogen population and pathogenicity towards elite germplasm is crucial to developing multifaceted management options that will secure the future sustainability of mungbean production.…”

Bacterial wilt of dry beans caused by Curtobacterium flaccumfaciens pv. flaccumfaciens: A new threat from an old enemy

“…Environmental stresses, in particular drought and warm temperature during daylight, increase disease progress and severity. The epidemiology of bacterial wilt contrasts with that of halo blight in Australian mungbeans and with common beans in the USA, with hotter and drier conditions most conducive for bacterial wilt disease development, and cooler, moister conditions most likely to result in halo blight epidemics (Harveson and Schwartz, ; Noble et al , ). Hence, geographic areas with hot summers (>30 °C) are the most favourable environments for bacterial wilt disease infections (Vidaver and Starr, ; Vidaver, ).…”

Two Homologues of the Global Regulator Csr/Rsm Redundantly Control Phaseolotoxin Biosynthesis and Virulence in the Plant Pathogen Pseudomonas amygdali pv. phaseolicola 1448A

“…phaseolicola; Pph) belongs to genomospecies 2, comprising five previously named species and 26 pathovars of P. syringae . Pph causes economically significant epidemics of halo blight on bean ( Phaseolus vulgaris ) and mung bean ( Vigna radiata ) and is a prominent research model in plant pathology [ 17 , 18 ]. Pph is ubiquitous and causes severe yield losses in cooler regions (18 °C–22 °C), whereas species of Xanthomonas become the prevalent bacterial pathogens in warmer environments, indicating a particular adaptation of Pph to temperature to maximize fitness.…”