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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. [ABSTRACT FROM AUTHOR]

Full genome sequences are presented for two isolates of Spartina mottle virus (SpMoV) from two accessions of the hybrid turf grass Cynodon dactylon × C. transvaalensis (Bermuda grass, green couch), originally from the USA but detected during post‐entry quarantine in Australia. Both isolates had a genome of 9,346 nucleotides, encoding a single polyprotein of 3,029 amino acids and predicted to be cleaved into 10 mature proteins. Phylogenetic analysis strongly supported placement in a new genus within the family Potyviridae. The isolates possess 715–780 × 11–12 nm flexuous virions and produce cylindrical (pinwheel) inclusions in infected cells. They were mechanically transmitted to several species in the Poaceae including Zea mays (maize, sweet corn), Chloris gayana (Rhodes grass), and Echinochloa colona (awnless barnyard grass). [ABSTRACT FROM AUTHOR]

A new approach for the simultaneous identification of the viruses and vectors responsible for tomato yellow leaf curl disease ( TYLCD) epidemics is presented. A panel of quantitative multiplexed real-time PCR assays was developed for the sensitive and reliable detection of Tomato yellow leaf curl virus-Israel ( TYLCV- IL), Tomato leaf curl virus (To LCV), Bemisia tabaci Middle East Asia Minor 1 species ( MEAM1, B biotype) and B. tabaci Mediterranean species ( MED, Q biotype) from either plant or whitefly samples. For quality-assurance purposes, two internal control assays were included in the assay panel for the co-amplification of solanaceous plant DNA or B. tabaci DNA. All assays were shown to be specific and reproducible. The multiplexed assays were able to reliably detect as few as 10 plasmid copies of TYLCV- IL, 100 plasmid copies of To LCV, 500 fg B. tabaci MEAM1 and 300 fg B. tabaci MED DNA. Evaluated methods for routine testing of field-collected whiteflies are presented, including protocols for processing B. tabaci captured on yellow sticky traps and for bulking of multiple B. tabaci individuals prior to DNA extraction. This work assembles all of the essential features of a validated and quality-assured diagnostic method for the identification and discrimination of tomato-infecting begomovirus and B. tabaci vector species in Australia. This flexible panel of assays will facilitate improved quarantine, biosecurity and disease-management programmes both in Australia and worldwide. [ABSTRACT FROM AUTHOR]

Summary Banana streak virus strain OL (BSV-OL) commonly infects new Musa hybrids, and this infection is thought to arise de novo from integrated virus sequences present in the nuclear genome of the plant. Integrated DNA (Musa6+8 sequence) containing the whole genome of the virus has previously been cloned from cv. Obino l’Ewai (Musa AAB group), a parent of many of the hybrids. Using a Southern blot hybridization assay, we have examined the distribution and structure of integrated BSV-OL sequences in a range of Musa cultivars. For cv. Obino l’Ewai, almost every restriction fragment hybridizing to BSV-OL was predicted from the Musa6+8 sequence, suggesting that this is the predominant type of BSV-OL integrant in the genome. Furthermore, since only two junction fragments of Musa/BSV sequence were detected, and the Musa6+8 sequence is believed to be integrated as multiple copies in a tandem array, then the internal Musa spacer sequences must be highly conserved. Similarly sized restriction fragments were detected in four BB group cultivars, but not in six AA or AAA group cultivars, suggesting that the BSV-OL sequences are linked to the B-genome of Musa. We also provide evidence that cv. Williams (Musa AAA group) contains a distinct badnavirus integrant that is closely related to the ‘dead’ virus integrant previously characterized from Calcutta 4 (Musa acuminata ssp. burmannicoides). Our results suggest that the virus integrant from cv. Williams is linked to the A-genome, and the complexity of the hybridization patterns suggest multiple sites of integration and/or variation in sequence and structure of the integrants. [ABSTRACT FROM AUTHOR]