Variability of Western Australian isolates of Sclerotinia sclerotiorum and the potential of Local Biological Control Agents

Stem rot disease caused by Sclerotinia sclerotiorum has emerged as a serious problem for canola (Brassica napus L.) production in Western Australia (WA) over the past few years where crop losses can be up to 40% in the worst affected crops. The biological characteristics and pathogenicity of the pathogen in WA is poorly understood. Also the potential for local biological control agents (BCAs) to be used in the management of the disease has not been explored. This paper provides preliminary data in these fields. One hundred and forty isolates of S. sclerotiorum were collected from WA canola growing regions for identification of biological characteristics which include colour of mycelia, growth rate, production of sclerotia, and pathogenicity. Other fungal isolates with potential biological control activity were collected from southern regions of WA. Colour of mycelia of Sclerotinia isolates varied from white, yellowish white, greyish white, brownish white, grey, dark grey to brown. Each isolate had its 24 and 48 hour growth rate recorded after sub-culture on PDA + ampicillin medium. ANOVA showed highly significant differences between growth rates of isolates 24 and 48 hours after being sub-cultured (P≤0.001). There were significant differences in number of sclerotia produced by each isolate. Two potential fungal biological control agents were found in WA, namely isolate KEN1 and isolate MTB1. These local fungal BCAs were found to be effective in inhibiting in vitro both the growth and ability to produce sclerotia of S. sclerotiorum

Pathogenicity test of Western Australian isolates of Sclerotinia sclerotiorum in canola

Stem rot disease caused by Sclerotinia sclerotiorum has emerged as a serious problem on canola (Brassica napus L.) production in Western Australia (WA) over the past few years where crop losses can be up to 40% in the worst affected crops. Hundreds of isolates of S. sclerotiorum have been collected from different canola growing regions of WA. As the majority of WA isolates of S. sclerotiorum have not been analyzed for their genetic characterization, analysis of genetic variation of WA isolates will be undertaken using classical and molecular techniques such as pathogenicity test, mycelial compatibility groups (MCGs), ITS sequencing, and cluster analysis. The experiments which started in March 2013, aim to use classical and molecular tools to identify groups of WA isolates of S. sclerotiorum from which isolates will be selected for the main studies on the management of S. sclerotiorum in canola. Accurate information of genetic diversity through research on characterization of the pathogen will lead to better understanding of the pathogen and will also benefit the breeding programs particularly aiming at breeding for disease resistance and moreover, could lead to developing better techniques for managing the disease. The paper provides an outline of the experiments and preliminary results

The impact of weather anomalies on shallot seed production in West Lombok, Indonesia

Shallot (Allium cepa L.) is one of the strategic commodities in Indonesia, where the Province of West Nusa Tenggara (NTB) is the third largest shallot-producing area. The main constraint in shallot cultivation is the limited availability of certified seeds and the weather strongly influences the cultivation. This paper discusses the impact of the 2021 weather anomaly on shallot seed production in West Lombok Regency, NTB Province, Indonesia. To produce and supply shallot seeds, the Super Phillip variety was planted in the period of May-June 2021 on farmers' land with an area of 4,000 m2 of alluvial soil. There was a weather anomaly in June 2021, in the form of high rainy days up to 12 days and an increase in rainfall of 176 mm (414%) above normal, resulting in damage to the bulb enlargement phase and Fusarium disease attacks on plants older than 40 days which resulted in harvest failures. This weather anomaly resulted in crop failure and losses in almost 100% of shallot seed production. To anticipate failures and minimize risks to the shallot farming system in the future, it is necessary to learn and transfer technology to interpret rainfall prediction information and design a shallot planting calendar

Biological control potential of trichoderma species and bacterial antagonists against Sclerotinia sclerotiorum on canola in Western Australia

Fifteen fungal and three bacterial biological control agents (F-BCA and B-BCA, respectively) were isolated from the canola production areas of Western Australia to investigate their potential for controlling sclerotinia stem rot (SSR) caused by Sclerotinia sclerotiorum under in vitro and field conditions. The capacity of these isolates to inhibit mycelial growth and sclerotia formation by S. sclerotiorum was assessed in dual culture tests in Petri dishes. Using Sanger Sequencing of the ITS regions, the F-BCAs were identified as Trichoderma atroviride (four isolates), T. gamsii (three isolates), T. koningiopsis (two isolates), T. longibrachiatum (two isolates), T. paraviridescens (two isolates), T. pseudokoningii (one isolate) and T. viridescens (one isolate). Four of the seven Trichoderma species (T. koningiopsis, T. gamsii, T. atroviride and T. viridescens) are reported for the first time from Western Australia. 16S rRNA sequencing identified B-BCA1 and B-BCA2 as Serratia proteamaculans and B-BCA3 as Ochrobactrum anthropi. There were significant differences among F-BCAs (P≤0.001) in their effect on radial mycelial growth (40–60% inhibition) and sclerotia formation (65–100% inhibition). Two isolates of T. atroviride (F-BCA12 and F-BCA15) completely blocked sclerotial formation of the pathogen on Potato dextrose agar + 10 ppm/L Aureomycin (PDAA). Incubation of sclerotia in soil inoculated with F-BCA indicated that sclerotia were colonized by the conidia of each F-BCA, and all sclerotia in the presence of F-BCAs failed to germinate on PDAA. The B-BCAs reduced radial mycelial growth by 57–59% and formation of sclerotia by 89–95%. Selected isolates of F-BCAs (T. koningiopsis and T. atroviride) and B-BCAs (O. anthropi and S. proteamaculans) significantly reduced disease incidence of S. sclerotiorum under glasshouse and field conditions. Field efficacy of tested BCAs was similar or better than the commercial fungicide Prosaro®

The impact of weather anomalies on shallot seed production in West Lombok, Indonesia

Shallot (Allium cepa L.) is one of the strategic commodities in Indonesia, where the Province of West Nusa Tenggara (NTB) is the third largest shallot-producing area. The main constraint in shallot cultivation is the limited availability of certified seeds and the weather strongly influences the cultivation. This paper discusses the impact of the 2021 weather anomaly on shallot seed production in West Lombok Regency, NTB Province, Indonesia. To produce and supply shallot seeds, the Super Phillip variety was planted in the period of May-June 2021 on farmers' land with an area of 4,000 m2 of alluvial soil. There was a weather anomaly in June 2021, in the form of high rainy days up to 12 days and an increase in rainfall of 176 mm (414%) above normal, resulting in damage to the bulb enlargement phase and Fusarium disease attacks on plants older than 40 days which resulted in harvest failures. This weather anomaly resulted in crop failure and losses in almost 100% of shallot seed production. To anticipate failures and minimize risks to the shallot farming system in the future, it is necessary to learn and transfer technology to interpret rainfall prediction information and design a shallot planting calendar