Pathogenicity and molecular detection of nectriaceous fungi associated with black root rot of avocado
2019
Black root rot of avocado associated with soilborne nectriaceous fungi is an aggressive disease
of nursery trees and young orchards transplants, causing tree stunting, wilt, severe root
necrosis, rapid decline and death within a year after planting. This study aimed to identify the
fungal genera associated with the disease, determine the causal agents of black root rot, and
develop a rapid molecular test for detection of key pathogens in avocado roots. A disease
survey in all Australian growing regions collected 153 nectriaceous fungal isolates from roots
of 91 symptomatic and healthy avocado trees and other hosts including peanut, papaya,
blueberry, custard apple and grapevine. The fungal isolates were identified with phylogenetic
analyses of ITS, β-tubulin and Histone H3 sequenced genes. Six genera were found associated
with black root rot; Calonectria, Cylindrocladiella, Dactylonectria, Gliocladiopsis, Ilyonectria
and Mariannaea. Glasshouse pathogenicity tests on 3–6 month-old avocado cv. Reed seedlings
determined Calonectria ilicicola to be an aggressive pathogen, causing stunting and death
within 5 weeks of inoculation. C. ilicicola isolated from peanut, papaya and custard apple also
caused black root rot in avocado, demonstrating a broad host range. Calonectria sp. from
blueberry and Dactylonectria macrodidyma, D. novozelandica, D. pauciseptata and D.
anthuriicola from avocado caused significant root rot but not stunting within 5–9 weeks.
Ilyonectria sp. from grapevine, and Cylindrocladiella pseudoinfestans, Gliocladiopsis peggii
and Ilyonectria sp. isolates from avocado were determined to be non-pathogenic. Three loopmediated isothermal amplification (LAMP) assays were developed for the detection of C.
ilicicola, D. macrodidyma and the Dactylonectria genus. The assays were sensitive and specific
at DNA concentrations of 1 pg/µl, 0.01 ng/µl and 0.1ng/µl for C. ilicicola, D. macrodidyma,
and Dactylonectria spp. respectively. Detection in avocado roots averaged from 12–26 min for
C. ilicicola and D. macrodidyma and 14–30 min for Dactylonectria spp.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
15
References
0
Citations
NaN
KQI