Jw. Buck et Jh. Andrews, Role of adhesion in the colonization of barley leaves by the yeast Rhodosporidium toruloides, CAN J MICRO, 45(6), 1999, pp. 433-440
To investigate whether leaf-surface yeasts adhere to the phylloplane in a t
wo-phase manner, with weak, nonspecific attachment followed by stronger, ti
me-dependent adhesion, we observed adhesion kinetics of the basidiomycete y
east Rhodosporidium toruloides to barley. While 50-60% of the cells adhered
in short-term assays (up to 3 h), fewer than 10% were adherent after 10 da
ys. Ten attachment-minus (Atr) mutants, deficient in phase I attachment, di
d not adhere after 5-day incubations, further suggesting a lack of stronger
, independent phase II adhesion. Long-term (5 day) adhesion was similar for
two isolates of R. toruloides and the ubiquitous leaf-surface fungus Aureo
basidium pullulans. Long-term adhesion of R. toruloides to leaves of a waxl
ess barley mutant was significantly greater than to leaves of the wild-type
cv. Bonus. Application of exogenous nutrients (dilute yeast carbon base) t
o resident, wild-type R. toruloides populations resulted in both a rapid re
colonization to the apparent carrying capacity of the leaves and an increas
e in the total adherent populations. Atr mutants recolonized barley segment
s, when supplied with nutrients, after more than 99% of the cells had been
removed by agitation. Therefore, adhesion of R. toruloides to leaves was no
t required for subsequent colonization of the phylloplane. Overall, these d
ata suggest that the frequency of yeast emigration from leaf surfaces, micr
obial growth rates, and leaf surface characteristics are major factors infl
uencing colonization of leaf surfaces.