Molecular detection of putative pathogens to determine any role in a causal relationship with abnormal vertical growth syndrome of macadamia

Zakeel, Mohamed Cassim Mohamed; Akinsanmi, Olufemi A.; Geering, Andrew D. W.

doi:10.1007/s10658-021-02333-5

Cited by 4 publications

(2 citation statements)

References 32 publications

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“…Prior to the extraction, fungal mycelium was scraped from the PDA plate into a sterile 2 ml microfuge tube and homogenized in a QIAGEN TissueLyser II at a frequency of 30 Hz for 1 min with a sterile 3 mm tungsten carbide bead. To obtain the total fungal community in plant samples, total DNA was extracted from 0.1 g of lyophilized leaf tissue using the CTAB method as described in Zakeel et al (2021a). DNA concentration was measured with a BioDrop spectrophotometer.…”

Section: Methodsmentioning

confidence: 99%

A fungal pathogen is unlikely to be the cause of abnormal vertical growth syndrome in macadamia

2022

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Abnormal vertical growth (AVG) in macadamia is a syndrome that reduces flowering and alters tree architecture, resulting in significant yield losses. The epidemiological parameters suggest the cause is probably a biotic agent with the ability to modulate plant hormone production or signalling. To determine if a fungal pathogen is the cause of AVG, we compared the fungal profile of macadamia trees with or without AVG symptoms using conventional culturing and DNA metabarcoding techniques. A diverse range of fungi was isolated from leaf, root and stem samples of macadamia cultivars HAES 344 and A16. The abundance of the isolated fungi was at least three‐fold higher in trees with AVG symptoms than in trees at the non‐AVG site. Similar results were obtained using DNA metabarcoding. Although the fungal genus Sebacina was the most dominant in the DNA metabarcoding, whereas Diaporthe (>40%) was dominant using the culturing techniques, no unique fungal species was consistently associated with all AVG samples. Therefore, we conclude that it is unlikely that the cause of AVG in macadamia is a fungal pathogen.

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Section: Methodsmentioning

confidence: 99%

A fungal pathogen is unlikely to be the cause of abnormal vertical growth syndrome in macadamia

2022

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“…The Australian macadamia industry is threatened by a syndrome known as abnormal vertical growth (AVG), which has an unknown etiology. Recent studies have hypothesized a biotic cause for AVG while dismissing previous hypothesis that AVG is caused by Bacillus megaterium, phytoplasmas or a geminivirus (Zakeel et al, 2020(Zakeel et al, , 2021. AVG is characterized by a vigorous upright growth habit with reduced lateral branching, flower production and nut set (O'Farrell, 2011).…”

Section: Introductionmentioning

confidence: 99%

Discovery of Single Nucleotide Polymorphisms for Resistance to Abnormal Vertical Growth in Macadamia

et al. 2021

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Abnormal vertical growth (AVG) syndrome is a serious threat to the Australian macadamia industry as it decreases the yield of nuts by as much as 70% per annum. A lack of information on the cause of AVG has hindered the development of an effective disease management strategy. Discovery of genetic markers associated with disease resistance can be used as tool for rapid selection of elite cultivars, hence helps in efficient disease management. Differences in field susceptibility of macadamia cultivars provide an opportunity for discovery of genetic markers that are associated with host resistance. REML mixed model analysis was performed to estimate the AVG rating of 51 cultivars from multiple origins using phenotypic data from 359 trees planted in four sites. Most of the Hawaiian cultivars were found as susceptible, while selections from the Australian macadamia industry breeding program were predominantly resistant. All the cultivars were genotyped for 13,221 DArTseq-based single nucleotide polymorphism (SNP) markers. A bulked sample analysis was performed using 20 genotypes each at the extremes of AVG phenotypic ratings. Ten SNP markers were predicted to be associated with AVG resistance and two arbitrarily selected SNP markers were validated using PCR and Sanger sequencing. Our findings suggest that AVG resistance in the commercial cultivars may be derived from the genomic introgression of Macadamia tetraphylla through interspecific hybridization. The results may support marker-assisted selection for macadamia germplasm with AVG resistance.

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Fungal composition, quantification of mycotoxins, and enzyme activity in processed Solanum tuberosum Linn (potato) products stored at different relative humidity

Danladi,

Ogbonna,

Ogbonna

et al. 2023

Journal of Applied Microbiology

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Aim Postharvest loss of potatoes at the peak of harvest is of global concern. This study aimed to determine the quality of stored processed potato products based on fungal composition, mycotoxin contamination and fungal enzyme activity. Materials and Methods Potato products from three cultivars (Caruso, Marabel and Nicola) were grouped as peeled or unpeeled, oven- or sun-dried and all samples were in flour form. Samples were incubated separately for six weeks at 25%, 74% and 87% relative humidities (RH) at 25 °C. The pH, moisture content, visible deterioration, mycotoxin, fungal identity by DNA sequencing, and enzyme activity were determined. Results Results of grouped products (based on variety, drying and peeling method) revealed that moisture content increased in the oven-dried samples and the pH value reduced after incubation. About 26% of the products at 87% RH showed visible deterioration, low amounts of fumonisin were detected in fermented potato product and nine fungal genera were identified across the three RH levels. Enzyme activities by Aspergillus niger, Fusarium circinatum and Rhizopus stolonifer isolates were confirmed. Conclusion RH influenced deterioration and fungal activities in some stored processed potato products. Low levels of fumonisin were detected.

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Molecular detection of putative pathogens to determine any role in a causal relationship with abnormal vertical growth syndrome of macadamia

Cited by 4 publications

References 32 publications

A fungal pathogen is unlikely to be the cause of abnormal vertical growth syndrome in macadamia

A fungal pathogen is unlikely to be the cause of abnormal vertical growth syndrome in macadamia

Discovery of Single Nucleotide Polymorphisms for Resistance to Abnormal Vertical Growth in Macadamia

Fungal composition, quantification of mycotoxins, and enzyme activity in processed Solanum tuberosum Linn (potato) products stored at different relative humidity

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