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ABSTRACTThe Ambrosia FusariumClade (AFC) comprises at least 16 genealogically exclusive species-level lineages within clade 3 of the Fusarium solanispecies complex (FSSC). These fungi are either known or predicted to be farmed by Asian Euwallaceaambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in the tribe Xyleborini as a source of nutrition. To date, only 4 of the 16 AFC lineages have been described formally. In the absence of Latin binomials, an ad hoc nomenclature was developed to distinguish the 16 species lineages as AF-1 to AF-16. Herein, Fusariumspecies AF-3, AF-5, and AF-7 were formally described as F. floridanum, F. tuaranense, and F. obliquiseptatum, respectively. Fusarium floridanumfarmed by E. interjectuson box elder (Acer negundo) in Gainesville, Florida, was distinguished morphologically by the production of sporodochial conidia that were highly variable in size and shape together with greenish-pigmented chlamydospores. Fusarium tuaranensewas isolated from a beetle-damaged Paŕa rubber tree (Hevea brasiliense) in North Borneo, Malaysia, and was diagnosed by production of the smallest sporodochial conidia of any species within the AFC. Lastly, F. obliquiseptatumwas farmed by an unnamed ambrosia beetle designated Euwallaceasp. 3 (E. fornicatusspecies complex) on avocado (Persea americana) in Queensland, Australia. It uniquely produces some clavate sporodochial conidia with oblique septa. Maximum likelihood analysis of a multilocus data set resolved these three novel AFC taxa as phylogenetically distinct species based on genealogical concordance. Particularly where introduced into exotic environments, these exotic mutualists pose a serious threat to the avocado industry, native forests, and urban landscapes in diverse regions throughout the world.

Rubus yellow net virus (RYNV) infects Rubusspecies and cultivars worldwide and is an essential component of raspberry veinbanding mosaic (RVBMD), a virus disease complex that causes serious decline in plant vigour and productivity. The virus is transmitted, probably in a semi-persistent manner, by the large raspberry aphid, Amphorophora idaeiin Europe, and A. agathonicain North America. The particles of RYNV are bacilliform in shape and measure 80-150 × 25-30 nm, similar to those of badnaviruses. A1.7 kb fragment of the viral DNA was amplified by PCR and then directly sequenced. Analysis of this sequence suggests that RYNV is possibly a distinct species in the genus Badnavirusand is most closely related to Gooseberry vein banding associated virus (GVBAV) and Spiraea yellow leaf spot virus, two other badnaviruses described recently. Using the sequence derived from the PCR-amplified viral DNA fragment, RYNV-specific primers were designed and used in PCR to assay for RYNV in a range of Rubusgermplasm infected with RYNV, with other unrelated viruses and virus-like diseases found in Rubus, and in healthy plants. RYNV was detected in all glasshouse cultures of RYNV-infected plants, whether alone or in complex infections with other viruses, but not from healthy Rubus plants, nor from plants infected with other viruses. It was also detected in field-grown raspberry plants with and without symptoms of RVBMD and in raspberry plants infected with RYNV by viruliferous A. idaei. RYNV was also detected by PCR in A. idaeifollowing access feeds on RYNV-infected plants of 1 h or more. PCR failed to amplify DNA from gooseberry infected with GVBAV confirming the specificity of the RYNV analysis. PCR detection of RYNV in dormant raspberry buds allows assays to be made outside the natural growing season, providing a useful application for plant introduction and quarantine programmes.

We have examined the effect of a strain of Banana streak virus(BSV-Cav) on the growth and yield of dessert bananas (MusaAAA group, Cavendish subgroup cv. Williams) in north Queensland, Australia. Healthy and infected plants were compared in a replicated field experiment over plant and first ratoon crops. In both crops, symptom expression followed a similar pattern, increasing to a maximum near the estimated time of bunch initiation, then decreasing in the period prior to bunch emergence. There was no evidence of plant-to-plant spread of virus, but the rate of transmission through suckers was 100. In the plant crop, the mean bunch weights of healthy and infected plants were not significantly different. However, BSV-Cav infection resulted in an 18 day delay in harvest, causing a 6 reduction in yield per annum. In the ratoon crop, the mean bunch weight of infected plants was 7 less than that of healthy plants, and the interval between the harvest of plant and ratoon crops was delayed by 9 days, resulting in a 11 reduction in yield per annum. Also, the mean length of fruit from infected plants was 5 less than that of healthy plants, resulting in a smaller percentage of fruit in the extra large size category. We conclude that in horticulturally favourable conditions typical of the tropical Australian banana industry, the effects of BSV-Cav infection on the growth and yield of Cavendish bananas are small.