Abstract
A total of one hundred and five isolates of Rhizoctonia belonging to 7 anastomosis groups (AGs) were obtained from the diseased roots and rhizosphere soils of bean, cucumber, eggplant, pepper and tomato plants grown in greenhouses in Samsun province (Black Sea region, Turkey) during the period 2011–2012. The isolates of Rhizoctonia spp. were examined for their cultural characteristics, anastomosis groups and pathogenicity. Of these, 83.8% were multinucleate Rhizoctonia solani (AG-2, AG-4, AG-5 and AG-6) and 16.2% were binucleate Rhizoctonia (AG-A, AG-E and AG-F). Sixty five of the isolates belonged to AG-4 which was the most frequent group (61.9%) in all greenhouses surveyed. Numbers of the isolates belonging to AG-2 (7.6%), AG-5 (6.7%) and AG-6 (7.6%) were 8, 7 and 8, respectively. Seventeen isolates recovered from greenhouses surveyed were identified as binucleate Rhizoctonia AG-A (1.9%), AG-E (6.7%) and AG-F (7.6%). All isolates of Rhizoctonia spp. tested for growth rates grew at temperatures of 10, 15, 20, 25 and 30°C, whereas they were completely inhibited at 5°C. The results of pathogenicity tests showed that the differences in virulence among isolates of Rhizoctonia spp. were statistically significant ( P < 0.001). The tests on bean seedlings showed that the highest disease severity was caused by AG-4 isolates. The disease severity index (DSI) of the R. solani AG-4 isolates ranged from 3.2 to 3.8. In addition, the isolates of three AGs belonging to binucleate Rhizoctonia spp. were generally found to be moderately virulent (DSI 2.0–2.4).
Highlights
Turkey is the fourth largest vegetable producer in the world after China, India and the USA (FAO, 2012)
A total of 434 isolates of Rhizoctonia spp. belonging to 9 anastomosis groups (MN R. solani AG-1, AG-4, AG-5, AG-6, AG-7, and BN Rhizoctonia AG-A, AG-B, AG-E and AG-K) were obtained from the roots and rhizosphere soils of bean and soybean plants grown in Samsun province, and AG-4 was found to be the most common group on bean and soybean plants (ERPER et al, 2011)
Summary
Turkey is the fourth largest vegetable producer in the world after China, India and the USA (FAO, 2012). Samsun province, located in the Black Sea region of Turkey, has the largest greenhouse production area in the region with a total cultivation area of 27 678 da and production of 130 696 tonnes/year (ANONYMOUS, 2015). There are three main groups of the Rhizoctonia form genus in the anamorphic classification: multinucleate (MN) Rhizoctonia (teleomorphs: Thanatephorus and Waitea), binucleate (BN) Rhizoctonia (teleomorphs: Ceratobasidium and Tulasnella), and uninucleate (UN) Rhizoctonia (teleomorph: Ceratobasidium) (SHARON et al, 2008). They exist as groups whose cultural characteristics, hosts and virulence differ (ERPER et al, 2006). The fungus is considered as a very destructive soilborne plant pathogen, with a broad host range, and causes diseases in a great variety of crops, including agronomical, ornamental and forestry species (GONZALEZ GARCIA et al, 2006; JAISWAL et al, 2014)
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