Pseudomonas syringae causing bacterial canker on apple trees in Brazil

Abstract

In March 2016, wilt and shoot blight were observed on five-year-old apple trees (Malus domestica) cultivar Maxi Gala in a commercial orchard in São Joaquim city, state of Santa Catarina, Brazil. Isolation on culture media, biolog, biochemical, LOPAT tests, and whole genome sequencing were performed. Koch's postulates were fulfilled on apple stems, leaves and fruits. The taxonomic position of a representative strain was determined by in silico DNA-DNA hybridization using the Genome-to-Genome Distance Calculator which showed 93.9% similarity with Pseudomonas syringae. Results of biolog and biochemical tests did not match those expected for pv. papulans, morsprunorum or syringae. To our knowledge this is the first report of P. syringae causing bacterial canker in commercial apple orchards in Brazil.

Viability and release of Neonectria ditissima ascospores on apple fruit in Brazil

“…Temperature is the main driver for development of European canker symptoms during the incubation period of the disease, whereas rain frequency is associated with lesion expansion and conidial production (Scheper et al, 2019). In Brazil, annual precipitation recorded in 2015 was 2301 mm (Araujo et al, 2020). In northern Germany, in regions such as Altenbruch and Oberndorf with high rainfall (837 and 801 mm, respectively) and moderate temperatures throughout the year, European canker has a particularly high potential to damage fruit production (Weber, 2014).…”

“…According to Adnan et al (2017), apple orchards with disease incidence exceeding 25% are classified as high risk for European canker and can be severely affected by fungus. In Brazil, mountainous regions in the state of Santa Catarina are the most suitable for apple production because of favourable climatic conditions; however, these conditions also favour the development of diseases (Araujo et al, 2019a(Araujo et al, , 2020. In Balochistan, higher canker incidence was observed in apple orchards established in warmer and wetter areas (Adnan et al, 2017).…”

“…The isolate used for inoculation was obtained from perithecia on mummified fruit occasionally found during the inspection of 200 apple trees in June 2018 [Colour figure can be viewed at wileyonlinelibrary.com] production (Scheper et al, 2019). In Brazil, annual precipitation recorded in 2015 was 2301 mm (Araujo et al, 2020). In northern Germany, in regions such as Altenbruch and Oberndorf with high rainfall (837 and 801 mm, respectively) and moderate temperatures throughout the year, European canker has a particularly high potential to damage fruit production (Weber, 2014).…”

“…Fuji was the pollinator, and one Fuji tree was planted for every five Gala trees. The soil of the experimental area is classified as humic cambisol (Araujo et al, 2020). The apple trees were managed with reduced applications of fungicides (about half that of a commercial orchard) for disease control, and insecticides and herbicides for insect and weed control.…”

“…ditissima ascospores were inoculated onto 1.5‐year‐old apple plants of cv. Gala grafted on Marubakaido rootstock with an M.9 interstem (commonly called a “filter”) according to Araujo et al (2020), to confirm Koch's postulates. Eight inoculated plants were maintained in plastic pots containing 1 kg of substrate comprising a mixture of soil, sand and manure in a 2:1:1 ratio.…”