Apple chlorotic leaf spot virus (ACLSV) ELISA Kit

A highly sensitive nested multiplex reverse transcription-polymerase chain reaction (nmRT-PCR) assay was developed for the simultaneous detection of Apple chlorotic leaf spot virus (ACLSV), Apple stem grooving virus (ASGV) and Apple stem pitting virus (ASPV) infecting pear trees. In the assay, a set of three forward primers specific to each of the three viruses and a universal reverse primer was used as external primers in the first-round PCR, which was followed by a second -round PCR developed previously. The nmRT-PCR assay was 10(4) times more sensitive than conventional mRT-PCR assay in detecting the three viruses in in vitro pear plantlets. This assay was subsequently used to detect these viruses in leaf and bark samples of cultivated and wild pear trees from orchards and demonstrated to be highly sensitive and reliable. This is the first report describing a use of nmRT-PCR for the sensitive and simultaneous detection of the three viruses infecting pear plants. The assay would be useful for the certification of pear planting materials and surveillance of nursery stocks.

Marubakaido (Malus Prunifolia Bork, var. ringo Asami has ben use as the main understock with dwarfing interstems, such as M. 9 and M. 26, for apple trees in Japan because it can easily be propagated by hardwood cuttings. The use of M. 9 as an interstem with Marubakaido resulted in severe growth retardation or death of trees because the M. 9 introduced into our area was infected with the apple-chlorotic-leaf-spot virus (ACLSV) to which Marubakaido is highly susceptible. Furthermore, when M. 9 was used as a rootstock, a similar reduction in tree growth occurred. ACLSV-free clone, M. 9- (minus), was developed from heat-treated shoot tips of M. 9 rootstock. The influence of this clone as a rootstock for 9 seasons and as an interstem for 4 years on the growth and yield of apple trees was evaluated in comparison with ACLSV-free M. 26 rootstock. 1. 'Fuji'/M. 9- scion/stock combination was smaller than 'Fuji'/M. 26 after 9 growing seasons. A severe growth reduction observed on 'Fuji'/M. 9 combination in the previous experiment was not observed in this study. Cumulative yield per trunk cross-sectional area was higher in M. 9- than it was in M. 26. It was not clear whether ACLSV or other latent viruses were responsible for the severe growth reduction. We determined that M. 9- is a promising rootstock for controlling the size of apple trees if the trees are planted at distances of 1.5 X 4 to 2 X 4.5 m. 2. When Marubakaido-N1, a weeping subclone selected from Nagano Prefecture, was used as the understock for 'Sekaiichi', 'Tsugaru' and 'Fuji' with M. 26 and M. 9- as the interstems, the 4-year-old trees with M. 26 grew less vigorously and produced smaller fruit than did the same combinations with M. 9- interstem. The incidence of burrknots and trunk flattening was more severe on M. 26 interstems; these 2 conditions may be related to the greater growth retardation on this rootstock. We consider M. 9- to be more promising than M. 26 as an interstem for controlling the size of apple trees.