Variability and interactions between endophytic bacteria and fungi isolated from leaf tissues of citrus rootstocks

Fungi and bacteria were isolated from surface disinfected leaf tissues of s everal citrus rootstocks. The principal bacterial species isolated were Alc aligenes sp., Bacillus spp. (including B. cereus, B. lentus, B. megaterium, B, pumilus, and B. subtilis), Burkholderia cepacia, Curtobacterium flaccum faciens, Enterobacter cloacae, Methylobacterium extorquens, and Pantoea agg lomerans, with P. agglomerans and B. pumilus being the most frequently isol ated species. The most abundant fungal species were Colletotrichum gloeospo rioides, Guignardia citricarpa, and Cladosporium sp. Genetic variability be tween 36 endophytic bacterial isolates was analysed by the random amplified polymorphic DNA (RAPD) technique, which indicated that B. pumilus isolates were more diverse than P. agglomerans isolates, although genetic diversity was not related to the host plants. In vitro interaction studies between G . citricarpa isolates and the most frequently isolated endophytic bacteria showed that metabolites secreted by G. citricarpa have an inhibitory growth effect on some Bacillus species, and a stimulatory growth effect on P. agg lomerans.