Polyphasic identification of preharvest pathologies and disorders in avocado cv. Hass

Abstract

Diseases and disorders are one of the main limitations ofavocado crops for export and national markets. However, theyare poorly studied in tropical countries such as Colombia. Theobjective of this research was to evaluate a polyphasic approachfor the diagnosis of pathologies and disorders associated withavocado cv. Hass in nurseries and crop fields located in Antioquia, Colombia. Results allowed the identification of several diseases and disorders present on different tissues in all stages of plant development. The root rot disease was associated with 10 microorganisms and two abiotic disorders. Different organs and tissues of avocado plants were affected by pathogens such as Lasiodiplodia theobromae, Colletotrichum gloeosporioides sensu lato, and Phytophthora palmivora. Pathogens that had not been previously reported in Colombia were identified, and among them P. palmivora, Fusarium oxysporum sensu lato, Phytopythium vexans, Phomopsis sp., and Pythium cucurbitacearum stand out. Abiotic disorders such as hypoxiaanoxia, root atrophy, fruit sunburn, and hailstorm damage were also identified. The etiology of peduncle ringing was not identified. Polyphasic diagnosis of pathologies and disorders is an appropriate approach as part of an integrated disease management program in avocado cv. Hass crop. This work is a reference tool on basic aspects associated with the detection of disorders and pathologies in avocado and the taxonomy of the microorganisms involved.

Development and validation of severity scales of avocado wilt complex caused by Phytophthora cinnamomi, Verticillium dahliae and hypoxia-anoxia disorder and their physiological responses in avocado plants

“…For the more advanced stages of these evaluated diseases, characteristic expressions of each pathology were observed. Phytophthora cinnamomi colonizes and destroys large portions of the root system, almost exclusively limited to secondary and tertiary roots, confirming previous reports (Zentmyer, 1984;Ramírez-Gil and Morales-Osorio, 2019). On the other hand, V. dahliae affects the roots and later the mycelium invades the vascular tissues, especially the xylem.…”

“…Therefore, the causal agents and disorders involved are difficult to identify under traditional diagnostic practices, especially in the first stage of development of the disease. This may lead to erroneous management practices that worsen the problem and cause large economic losses (Ramírez-Gil et al, 2017;Rodríguez et al, 2017;Hardham and Blackman, 2018;Ramírez-Gil, 2018;Ramírez-Gil and Morales-Osorio, 2019). AWC can affect various tissues in the avocado, especially the roots, inducing several symptoms.…”

“…The fungus Verticillium sp. has been less studied, but has been increasingly recognized as important because of problems of root rot associated with the disorder hypoxia-anoxia, especially under tropical conditions in Colombia (Ramírez-Gil et al, 2017;Rodríguez et al, 2017;Ramírez-Gil, 2018;Ramírez-Gil and Morales-Osorio, 2019). Hypoxia-anoxia is not only considered a disorder that causes the death of avocado plants, but it can also be a stress factor that is highly related to the presence of P. cinnamomic (Stolzy et al, 1967;Ploetz and Schaffer, 1989;Sanclemente et al, 2014;.…”

“…Hypoxia-anoxia is not only considered a disorder that causes the death of avocado plants, but it can also be a stress factor that is highly related to the presence of P. cinnamomic (Stolzy et al, 1967;Ploetz and Schaffer, 1989;Sanclemente et al, 2014;. This disorder is associated with soil moisture, which reduces the gas content in the porous space of the soil volume (Stolzy et al, 1967;Sanclemente et al, 2014;Ramírez-Gil and Morales-Osorio, 2019).…”

Mitigation of the Adverse Effects of the El Niño (El Niño, La Niña) Southern Oscillation (ENSO) Phenomenon and the Most Important Diseases in Avocado cv. Hass Crops

“…This pathology can be caused by biotic and abiotic factors, and each one can induce similar specific symptoms in the host. Usual symptoms in avocado plants are foliar yellowing, tissue flaccidity, growth retardation, excessive flowering and fructification in adult trees, defoliation, dieback, root rot, and plant death [ 30 , 31 ]. Avocado roots can be seriously affected by AWC causing large losses, usually between 45–90%, but which could reach 100% if no prompt and appropriate control measures are performed during all stages of crop establishment, growth, and development [ 27 , 29 , 32 ].…”