L. Korsten et al., EVALUATION OF BACTERIAL EPIPHYTES ISOLATED FROM AVOCADO LEAF AND FRUIT SURFACES FOR BIOCONTROL OF AVOCADO POSTHARVEST DISEASES, Plant disease, 79(11), 1995, pp. 1149-1156
Bacteria isolated from Fuerte avocado leaf and fruit surfaces were eva
luated for in vitro antagonism toward Dothiorella aromatica. Thirty-th
ree bacteria exhibiting pronounced growth inhibition were further test
ed for antibiosis against Colletotrichum gloeosporioides, Thyronectria
pseudotrichia, Phomopsis perseae, Pestalotiopsis versicolor; and Fusa
rium solani. Optimum disease-reducing concentrations of Bacillus subti
lis (isolate B246) exhibiting the highest degree of antibiosis were de
termined according to a checkerboard-type titration assay, by artifici
al inoculations on Fuerte and Edranol avocado fruit in the laboratory.
Various concentrations (10(5), 10(6), 10(7), and 10(8) cells ml(-1))
of B. subtilis were also incorporated into commercial Tag-wax and appl
ied to Hass avocado fruit in the packinghouse for control of anthracno
se, Dothiorella/Colletotrichum fruit rot complex (DCC), and stem-end r
ot (SE). In the artificial inoculation study, increasing concentration
s of B. subtilis were effective against increasing concentrations of C
. gloeosporioides, F. solani, and T. pseudotrichia. Control of D. arom
atica was significant at the lower (10(3) and 10(4) cells ml(-1)) path
ogen concentrations, whereas inhibition of P. perseae and P. versicolo
r was more readily achieved at the lower (10(5) and 10(6) cells ml(-1)
) antagonist concentrations. In the packinghouse, a B. subtilis concen
tration of 10(7) cells ml(-1) significantly reduced anthracnose and SE
externally and internally, while the lower B. subtilis concentrations
(10(5) and 10(6) cells ml(-1)) were effective against internal DCC. B
ased on treatment means of all external and internal postharvest disea
se data, all B. subtilis concentrations performed equally well in cont
rolling postharvest diseases.