New Zealand Journal of Crop and Horticultural Science abstracts
Potyviruses in New Zealand buttercup squash (Cucurbita maxima Duch.):
yield and quality effects of ZYMV and WMV 2 virus infections
J. D. FLETCHER
A. R. WALLACE
New Zealand Institute for Crop & Food
Research Limited
Private Bag 4704
Christchurch, New Zealand
email: FletcherJ@crop.cri.nz
B. T. ROGERS
New Zealand Institute for Crop & Food
Research Limited
Lawn Road
Hastings, New Zealand
Abstract The Obisu type `Delica' buttercup squash
(
Cucurbita maxima Duch.) was inoculated at early, mid, and late stages
of growth with zucchini yellow mosaic virus (ZYMV) and watermelon mosaic virus
2 (WMV2). The results of these field trials demonstrated that early- and
mid-season ZYMV infections and early-season WMV 2 infections caused serious
yield losses and adverse quality effects in comparison with yields from
uninoculated plots. Total yield losses from ZYMV were 48% for early-season and
26% for mid-season infections. Yield losses from WMV 2 were statistically
significant only after early infection (38%). Numbers of marketable fruit were
similarly affected as was marketable fruit weight and incidence of fruit
blistering. For example, early season single or combined infections of ZYMV or
WMV 2 reduced the mean marketable yield of `Delica' from 84 to 23% of the total
yield of uninoculated plots. In a second trial, the effect of a mid-season
infection on three squash types showed that the Miyako type was more sensitive
to losses in number and fruit weight than Obisu or Arjihei types. In both
trials, mixed infections of ZYMV and WMV 2 caused yield effects that were
similar to those associated with ZYMV alone. We conclude that ZYMV and WMV 2
infection either before or during the flowering period will reduce fruit size,
affect marketable quality through fruit blistering, and reduce fruit numbers.
It is therefore important that measures to reduce or eliminate virus infection
are taken early in the growing season. Seed from infected fruits were grown and
assayed for virus transmission. Incidences of up to 3.5% for ZYMV and 5% for
WMV 2 were recorded, demonstrating that both ZYMV and WMV 2 can be transmitted
by the seed of infected
C. maxima fruit. We believe that the
reintroduction and spread of ZYMV, and possibly WMV 2, into buttercup squash
growing areas will continue if seed health is not addressed, in addition to
practicing normal virus disease control strategies.
Keywords yield; quality; zucchini yellow mosaic virus; ZYMV;
watermelon mosaic virus 2; WMV2; buttercup squash; Cucurbita maxima;
field trials; seed-borne virus transmission
H99029
Received 4 August 1999; accepted 18 November 1999
PDF file of entire paper: medium quality (711K); (scanned from paper original: notes about this process)
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