Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc), poses a major threat to banana production globally. A variant of Foc that originated in Southeast Asia, called tropical race 4 (TR4), was detected on a Cavendish banana export plantation (Metocheria) in northern Mozambique in 2013. Foc TR4 was rapidly disseminated on the farm, and affected approximately half a million plants within 3 years. The fungus was also detected on a second commercial property approximately 200 km away (Lurio farm) a year later, and on a small-grower’s property near Metocheria farm in 2015. Surveys in Mozambique showed that non-Cavendish banana varieties were only affected by Foc race 1 and race 2 strains. The testing of Cavendish banana somaclones in northern Mozambique revealed that GCTCV-119 was most resistant to Foc TR4, but that GCTCV-218 produced better bunches. The occurrence of Foc TR4 in northern Mozambique poses a potential threat to food security on the African continent, where banana is considered a staple food and source of income to millions of people. Cavendish somaclones can be used, in combination with integrated disease management practices, to replace susceptible Cavendish cultivars in southern Africa. The comprehensive testing of African cooking bananas for resistance to Foc TR4 is required, along with the improvement of biosecurity and preparedness of growers on the African continent.

In this study, the putative phytoplasma species causing coconut lethal yellowing disease in Mozambique and Tanzania were characterized. The 16S rRNA and secA genes were sequenced. Phylogenetic analysis revealed that Mozambican coconut phytoplasmas belong to three different types: 'Candidatus Phytoplasma palmicola' 16SrXXII-A, a second strain that was previously isolated in Tanzania and Kenya (16SrIV-C), and a third strain that was different from all known lethal yellowing phytoplasma species. The third strain potentially represents a novel species and is closely related to pine phytoplasma. Co-infection with 'Ca. Phytoplasma pini'-related and 'Ca. Phytoplasma palmicola' 16SrXXII-A strains was observed. Furthermore, sequence variation in 'Ca. Phytoplasma palmicola' at the population level was consistent with purifying selection and population expansion.

In the spring of both 2003 and 2004, serious outbreaks of a suspected bacterial leaf spot disease were observed on tuberous non-stop begonia plants ( Begonia × tuberhybrida cvs. Futta, Kleo, Apricot and Red) and strawberry begonia ( Saxifraga sarmentosa ) grown for potted production in commercial greenhouses located in Adana, Manisa, Yalova and Istanbul provinces of Turkey. The initial symptoms of the disease were small round spots and angular necrotic areas on leaf surfaces. A general leaf yellowing and necrosis followed the spotting. Defoliation, open stem canker and vascular discoloration were observed on plants in advanced stages of the disease. Disease incidence was recorded in the range of 15-30% over two years. Isolations were made from leaves and stems of the affected plants on yeast dextrose chalk agar producing yellow-coloured mucoid and convex colonies. Eighteen bacterial isolates were purified and used for further studies. All isolates were characterized as non-sporing, Gram negative, rodshaped, motile, aerobic, oxidase-negative, catalase-positive and amylolyticpositive (Schaad et al ., 2001) and all were identified as Xanthomonas axonopodis pv. begoniae (Xab; Vauterin et al ., 1995) based on fatty acid methyl ester analysis (Yeditepe University, Istanbul, Turkey) with similarity indices ranging from 51 to 77% (Chase et al ., 1992) and indirect-ELISA tests (Agdia BRA 23700) (Benedict et al ., 1990). All of the test results were similar to those of the reference strain used in this study.Pathogenicity was confirmed by spray inoculation of the leaves on tuberous begonia and strawberry begonia plants. Sterile distilled water and a reference strain (BPIC 2013, X. axonopodis pv. begoniae ) were used as negative and positive controls respectively. All plants were covered with polyethylene bags for 48 hour at 25 ° C. After inoculation, water-soaked and necrotic symptoms were observed on tuberous and strawberry begonia plants within 5-7 days. No symptoms were observed on control plants. This is the first report of Xab in commercial floriculture in Turkey and also the first report of infection of strawberry begonia by this pathogen.

No abstract

No abstract