622 Manuel Malfeito-Ferreira et al.
wine –A. carbonariusandtoalesserextentA. niger. Recently, a new species of sec-
tionNigriisolated from grapes and OTA non-producer –A. ibericus– was proposed
(Serra et al. 2006), being likely that new species can enlarge that section in the near
future. In fact, with recent work on the molecular characterization of a Southern
Europe population of black aspergilli isolated from grapes it was concluded that
these represent a complex of species, where some of them are peculiar to grapes
(Perrone et al. 2006b). Another study performed with strains isolated from grapes
in Italy indicated thatA. tubingensisis able to produce OTA and that, together with
A. carbonariusandA. niger, it may be responsible for the OTA contamination of
Italian wines (Perrone et al. 2006a). Some references in the literature also describe
the occurrence of the yellowishA. ochraceus(belonging to theAspergillussection
Circumdati) and the blue-greenPenicilliumspecies on grapes (Frisvad et al. 2004),
but its importance seems to be minor when compared with black aspergilli.
The evaluation of OTA production by fungi on infected grapes is essential to
establish the real producing ability by the different species because the results of
tests on synthetic culture media are not always coincident with in vivo determi-
nations (Bell ́ı et al. 2007). Overall, mostA. carbonariusstrains have the ability
to produce OTA in grapes whereas the proportion is lower in the other toxigenic
species (Perrone et al. 2006a, 2006b).
From a scientific point of view, precise strain identification of OTA fungi pro-
ducers is important to establish the phylogenetic relationships among species, to
recognize the mycota of foodstuffs, and tounderstand the peculiarities and ecologi-
cal needs of the species. However, from a viticultural and enological point of view,
it will be much more important to establish the environmental conditions that are
ideal for OTA fungi producers on grapes than their identification.
11.2.4.2 Factors Affecting Fungal Growth and OTA Production
The primary sources ofA. carbonariusandA. nigerare soil, bunch remnants or
vine trash on soil vineyards, which are transported by wind from soil onto berry
surfaces (Leong et al. 2006a; Hocking et al. 2007). Generally, the colonisation of
grape bunches by black aspergilli and other fungi occurs when berry skin damage
allows the entry into fruit tissues, where the low pH and high sugar content under
aerobic conditions provide a competitive advantage for moulds. However, fungal
invasion may occur without visible symptoms (Bell ́ı et al. 2007). As a rule, the com-
petition among contaminant microorganisms is more favourable toBotrytis cinerea,
the agent responsible for common grey rot. However, other rot processes, such as
sour rot and brown rot, can occur together with black aspergilli. The population
dynamics of fungi outside or inside grape berries with skin damage is still poorly
known, as it is difficult to establish which environmental conditions promote the
dominance of each fungal species. Nevertheless, it has been shown that high tem-
peratures (30◦C) and high relative humidity, between 80% and 100%, give rise to
higher amounts of OTA produced byA. carbonariuson grapes (Bell ́ı et al. 2007),
suggesting that such conditions give competitive advantages to the black aspergilli
population. Medina (2007) also showed thatA. carbonariusgrowth was favoured