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Bacterial diseases of onion and ways of lowering of their damage in the conditions of Moldova

Author: Ţercovnaia Valentina
Degree:doctor of agriculture
Speciality: 06.01.11 - Plant Protection
Scientific consultant: Petru Patron
doctor habilitat, professor
Institution: Institute for Plant Protection and Ecological Agriculture of the ASM
Scientific council: DH 23-06.01.11-25.12.03
Institute for Plant Protection and Ecological Agriculture of the ASM


The thesis was presented on the 26 November, 2009
Approved by NCAA on the 11 February, 2010


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onion, bacterial diseases, identification, pathogenicity, disease control, spray schedules, efficiency.


Last years plants of onion are strongly affected by the bacterial diseases. However, there are currently no specific recommendations for the control of disease. Owing to it the aim of our work we are carry out the research work on identification of bacteria, ways to reduce degree of their harmfulness for working out of recommendations of further use of preparations on onion.

The basic research was carry out in scientific research institute (Tiraspol) for the past four years (2004-2008). Suspect bacterial colonies were characterized by biochemical and physiological reactions, fatty acid methyl ester profiles, and by the polymerase chain reaction by standard techniques.

The causal agent of bacterial diseases occurred at different stages of onion cultivation, caused spots on leaves and flower stalks, bulb rot, unfull-value seeds production with consequent disease losses.

It was determined that bacterial diseases of onion are caused by Pseudomonas gladioli pv. alliicola Severini 1913, Erwinia carotovora subsp. carotovora (Jones 1901) Dye 1969, Pseudomonas fluorescens (Trevisan 1889) Migula 1895, Pantoea agglomerans (Ewing and Fife 1972) Gavini et al. 1989, Pseudomonas syringae van Hall 1902. This is the first report of bacte-rial diseases of onion caused by a P. syringae pathovar in the conditions of irrigated agriculture of Moldova.

In the course of work dependence of semiology from a life cycle stage is defined of a host plant, and also from connection to a certain part of a plant.

It was studied the relationship of causal agents of bacterial diseases of onions among themselves; are established the sources of preservation and accumulation of a bacterial infection; is tracked the "stream" of movement of the bacteria, affected of onion, on a plant. The results of experiments showing a effective preparations for struggle with bacterial diseases of onion, was established optimum terms of their application.

In this study as a result of the investigations carried out during the years 2005-2008 we have noted: disinfection of contaminated external and internal tissues of seeds with heat treatment at 65 ºС and 75 ºC for 3 hours with further processing of seeds by Thiram 65 % w. p., weed management, utilizing field-curing and storing onions - all reduced bacterial disease levels. When combined with chemical control with the Quadris 25 % c. s. at 0,5 l ha-1 on a 10-day spray schedule in an integrated pest management strategy, they provide excellent levels of control for bacterial disease of onion. Copper compounds Cuproxat 34,5 % c. s. taken as a standard was less effective of previous fungicide.

Results on application of Quadris 25 % c. s. have been used in technological process of State Unitary agricultural enterprise "Dnestr" (Tiraspol) in the periods since march 2007 till march, 2008. According to the received results on each hectare of a skilled site, where the prepa-ration of enterprise Quadris 25 % c. s. was applied in struggle against bacterial diseases of on-ions are received profits 8145 lei, that more than a reference variant (by Cuproxat 34,5 % c. s..) on 58 %.