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Survey and characterization of Ralstonia solanacearum in solanaceous crops in Tanzania

Hellen Kanyagha: The Ohio State University

<div>Tomato is one of the most important horticultural crops in Tanzania in terms of productivity and economic importance. However, cases of bacterial wilt, caused by <em>Ralstonia solanacearum</em>, are increasing at an alarming pace, especially in prime tomato producing regions. During a survey conducted from May to July 2017, 128 fields were visited in the Iringa and Mbeya (southern highland), Morogoro and Tanga (coastal and medium altitude), and Arusha (northern highland) regions of Tanzania. Bacterial wilt was detected in the majority (55%) of fields in solanaceous crop plants, with incidences ranging from 2% to 80%. Tanga region had the most infected fields and Iringa had the fewest. One hundred twenty-one isolates of <em>R. solanacearum</em> were recovered from infected plant tissue and soils (tomato: 59 isolates, potato: 49, eggplant: 5, pepper: 2, soil: 6) and assessed for numerous characteristics. All isolates were confirmed as <em>R. solanacearum</em> using PCR with species-specific primers 759/760. The isolates were classified into biovar using their ability to utilize cellobiose, lactose, maltose, dulcitol, mannitol, and sorbitol and into phylotype using multiplex PCR with phylotype-specific primers. All 121 isolates belonged to biovar 3 and were confirmed as phylotype III.</div>