Abstract
The effects of environmental conditions on the variability in germination dynamics of
Plasmopara viticola
oospores were
studied from 1999 to 2003. The germination course was determined indirectly as the relative infection incidence (RII)
occurring on grape leaf discs kept in contact with oospores sampled from a vineyard between March and July. The time
elapsed between 1 January and the infection occurrence was expressed as physiological time, using four methods: (i) sums
of daily temperatures
>
8
°
C; (ii) hourly temperatures > 10
°
C; (iii) sums of hourly rates from a temperature-dependent
function; or (iv) sums of these rates in hours with a rain or vapour pressure deficit
≤
4·5 hPa (hydro-thermal time, HT).
An equation of Gompertz in the form RII
=
exp[
−
a
· exp(
−
b
· HT)] produced an accurate fit for both separate years
(
R
2
=
0·97 to 0·99) and pooled data (
R
2
=
0·89), as well as a good accuracy in cross-estimating new data (
r
between
observed and cross-estimated data were between 0·93 and 0·99,
P
<
0·0001). It also accounted for a great part of the
variability in oospore germination between years and both between and within sampling periods. Therefore, the equation
of Gompertz (with
a
=
15·9
±
2·63 and
b
=
0·653
±
0·034) calculated over hydro-thermal time, a physiological time
accounting for the effects of both temperature and moisture, produced a consistent modelling of the general relationships
between the germination dynamics of a population of
P. viticola
oospores and weather conditions. It represents the
relative density of the seasonal oospores that should have produced sporangia when they have experienced favourable
conditions for germination
Lingua originale | Inglese |
---|---|
pagine (da-a) | 216-226 |
Numero di pagine | 11 |
Rivista | Plant Pathology |
DOI | |
Stato di pubblicazione | Pubblicato - 2008 |
Keywords
- Vitis vinifera
- environmental conditions
- grapevine downy mildew
- modelling
- primary inoculum