Potato spindle tuber viroid eradicated in Western Australia
Potato spindle tuber viroid (PSTVd) was detected for the f irst time in an isolated hydroponic greenhouse tomato (Lycopersicon esculenturn) erop in the great southern region of Western Australia (WA). An urgent eradication plan was activated because of the highly contagious nature of the pathogen. The tomato erop on the infected property was destroyed and the greenhouses and surrounding area were decontaminated. Surveys of 15 other hydroponic tomato crops did not detect any other PSTVd infected tomato plants in WA.
Potato spindle tuber viroid: alternative host reservoirs and strain found in a remote subtropical irrigation area
During 2007–2012, Potato spindle tuber viroid (PSTVd) was detected in volunteer cultivated, wild and native plants during studies to determine whether Pospiviroids occur within the isolated, sub-tropical, Gascoyne Horticultural District (GHD) in central coastal Western Australia (WA). PSTVd was detected infecting volunteer crop plants of tomato, pepper and chilli; introduced weed species Solanum nigrum (blackberry nightshade), Datura leichhardtii (thornapple) and Nicandra physalodes (apple-of-Peru) (Solanaceae), and Conyza bonariensis (flaxleaf fleabane) (Asteraceae); and Australian native species Atriplex semilunaris (annual saltbush), Rhagodia eremaea (thorny saltbush) (Chenopodiaceae), and Streptoglossa sp. (Asteraceae). PSTVd was also detected infecting Physalis angulata (wild gooseberry) in the Ord River Irrigation Area (ORIA), Kimberley region in north-west WA. Comparison of sequences from the three complete and 18 partial RNA nucleotide sequences obtained from 20 GHD and one ORIA isolates with those of published sequences showed that their highest nucleotide sequence identities were to isolate AY962324 belonging to the Chittering strain from south-west WA. On phylogenetic analysis, the three completely sequenced GHD PSTVd isolates grouped within a cluster of isolates from tomato and P. peruviana. These results show that a naturally occurring PSTVd inoculum reservoir is present in the GHD. This reservoir explains the occurrence of repeated PSTVd infections in different years in field crops of tomato, pepper and chilli growing in its market gardens and small farms. These findings have implications concerning PSTVd spread in intensive solanaceous crop field production systems in other subtropical regions of the world.
SEED TRANSMISSION OF POTATO SPINDLE TUBER METAVIRUS THROUGH THE OVULE OF SCOPOLIA SINENSIS
Potato spindle t uber metavirus was transmitted through the seeds of Sco olia sinensis. P ollination of infected flowers with pollen from S. sinensis p lants resulted in 71 % infected s eedlings, indicating transmissyon through the ovules. Infected seeds germinated wxthout delay. Symptoms developed within 3-8 weeks after emergence of seedlings and consisted of lesions, n ecrotic s potting on the leaves, and stunting. In view of the facility with which seed transmission occurs, plants used in seed production should be selected with care.