The Role of Saprotrophy and Virulence in the Population Dynamics of Botrytis cinerea in Vineyards

Abstract

Change in relative frequencies of the three main genetic types of Botrytis cinerea (Group I, Group II vacuma, and Group II transposa) were monitored over time from 1998 to 2000 in three Bordeaux vineyards not treated with fungicides. During 2000, Group I isolates, detected mostly at flowering comprised only 2.5% of the entire population. Within Group II, the complementary frequencies of vacuma and transposa isolates differed significantly depending on grapevine phenological stages and organs. Every year and at all sites, including one noble rot site, transposa isolates dominated at every stage, particularly on overwintering canes and at harvest (greater than 86.7% on berries). The complementary frequency of vacuma isolates reached a maximum on senescing floral caps (between 23.5 and 71.4%) and then decreased significantly until harvest on leaves and berries. In pathogenicity tests on grape berries, transposa isolates were significantly more virulent than were vacuma isolates. Mycelial growth rate was negatively correlated with virulence, notably on leaves in transposa and with double resistance to the fungicides carbendazim and vinclozolin. In vacuma, this double resistance was positively correlated with virulence on leaves. Change in the vacuma and transposa frequencies was most likely caused by differences in saprotrophic and pathogenic fitness. Possible interactions between fungicide resistance profiles and fitness are discussed.

Botrytis cinerea in raspberry in Serbia I: Morphological and molecular characterization

“…This may support an observation of Giraud et al (1997) that the share of vacuma isolates decreases during the growing season. Significant decreases in the frequency of vacuma isolates during the vegetation period have also been recorded in France, Italy and Austria (Martinez et al, 2005;De Miccolis Angelini et al, 2006;Achleitner, 2008). However, further investigation with a more appropriate sampling design is needed in order to make a final conclusion about the dynamics of frequency of vacuma isolates over the growing season.…”

“…Transposa isolates were also dominant in vineyards in France (Giraud et al, 1997;Martinez et al, 2005), Austria (Achleitner, 2008), and Croatia (TopalovecPintarić et al, 2004), as well as in strawberry in Croatia (Milićević et al, 2006).…”

“…Further studies have revealed significant differences regarding the prevalence of vacuma and transposa isolates on different host plants (Giraud et al, 1999). In addition, Martinez et al (2003Martinez et al ( , 2005 found that vacuma isolates were mostly of mycelial type and with higher growth rate than transposa isolates, while Giraud et al (1999) reported difference in fungicide resistance frequencies in transposa and vacuma isolates. Since successful management of grey mould disease is based on the depth of our knowledge of the pathogen, information on the genetic structure of its population could be a useful tool for developing effective control strategies.…”

Autofluorescence of grape berries following Botrytis cinerea infection

“…The B. cinerea strain 234, belonging to the transposa genetic type (Group-II), was used because strains of this type are more aggressive on grape berries than vacuma Group-II strains (Martinez et al, 2005). Provided by UMR Santé végétale (INRA-ENITA, Bordeaux, France), a detailed phenotype of this isolate has been described by Martinez et al (2003).…”

“…Various infection pathways have been described to establish epidemiological relationships between these first attacks, occurring early in the season, and the typical infections of maturing berries (Elmer and Michailides, 2004). Gray mold development on grape berries depends on the genetic structure of the pathogen population (Martinez et al, 2005), but is also driven by some key factors, including climatic conditions, cluster architecture and berry susceptibility (Pezet et al 2004;Elmer and Michailides, 2004). Berry infection result mostly from i) conidia germination and penetration favored by the presence of wounds at the surface of the fruit, in particular insect injuries (Fermaud and LeMenn, 1992;Miklota et al 2003;Holz et al 2004), ii) mycelial spread from one berry to the next which has been associated with severe losses.…”