Phytobacteriological studies related to the native (Olea cuspidata Wall.) and introduced (Olea europaea L.) olive species in Nepal
Author(s)
Lamichhane, Jay Ram
Date Issued
February 2, 2011
Type
Doctoral Thesis
Abstract
Two olive species, one introduced from Europe (Olea europaea L.) and cultivated in different Districts and the other one the native species of Nepal (Olea cuspidata Wall.), were studied regarding phytobacteriological aspects. Among the two olive species, the first was widely studied while no study is available on O. cuspidata. In particular, the presence and/or appearance of olive knot disease, the quali-quantitative composition of phylloplane bacterial populations of these species from different Districts, the epiphytic survival of Pseudomonas savastanoi pv. savastanoi (Psav) (the causal agent of olive knot disease) both on O. europaea and O. cuspidata, the susceptibility of these species to Psav and the antagonistic activity of the phylloplane bacteria against Psav in vitro have been studied. Different strains of Psav isolated from different geographic origins were used.
No presence of olive knot disease was found on Olea spp. surveyed during the study in Bajura, Dolpa and Kathmandu Districts. Whereas the disease was found on O. europaea, introduced two decades ago, in a commercial orchard of Makwanpur District. No presence of Psav on Olea phylloplane was found. The size of bacterial epiphytic populations ranged from very low (2.39 x 100 CFU/cm2) to very high (1.09 x 105 CFU/cm2). No quantitative differences statistically significant were found on Olea phylloplane sampled in the three Districts. Fifteen bacterial species were identified as colonizers of Olea phylloplane in Nepal which are so far different than those found in south-east Italy. Both the olive species were dominated by Pantoea agglomerans (former Erwinia herbicola). No qualitative differences statistically significant were seen on Olea phylloplane sampled in three Districts mentioned above.
Olive species showed a significant influence on bacterial epiphytic survival since Psav better multiplies on O. cuspidata compared to O. europaea. Leaf age and bacterial strains did not influence significantly the epiphytic survival of the pathogen. O. cuspidata showed higher susceptibility to Psav strains than O. europaea to artificial inoculations although no difference statistically significant was found. Plant age did not influence significantly host-pathogen interaction. The bacterial strains showed significant differences among them in terms of symptom appearance, knot size and bacterial populations into the knots. None of the phylloplane bacteria inhibited in vitro the growth of P. savastanoi pv. savastanoi.
Additional information
Dottorato di ricerca in Protezione delle piante
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