Races and virulence of Fusarium oxysporum f.sp. cubense on local banana cultivars in Kenya

Abstract

SummaryVirulence of 31 Kenyan isolates of Fusarium oxysporum obtained from bananas showing symptoms of Panama disease was tested against the differential banana cvs Bluggoe, Gros Michel, Dwarf Cavendish, and two other local cvs Muraru and Wang'ae. Seventeen isolates were assigned to either race 1 or race 2 of F. oxysporum f.sp. cubense (FOC). Race 4 was not apparent in this sample of 31 isolates from Kenya as none were pathogenic to cv. Cavendish, and no wilted Cavendish have been observed in field surveys in Kenya. Races could not be assigned to 12 isolates as they were virulent on more than one differential cultivar, and two were apparently not pathogenic. All isolates assigned to races 1 and 2 belonged to the VCG bridging complex 0124/5/8/20, but some other isolates belonging to this VCG complex could not be assigned to race. All five isolates assigned to VCG 01212 could not be assigned to known races. Considerable variability thus exists within FOC isolates within this region. Local cultivars of banana showed differential resistance to the pathogen. The interaction of cultivars and isolates on the level of disease was significant. Overall, cv. Wang'ae was the most susceptible to most of the isolates tested, regardless of their race, and could therefore be used as a reference cultivar in pathogenicity tests of isolates of FOC in the East African region. Of the cultivars tested that are widely grown on smallholder farms in Kenya, Muraru was the least susceptible.

Evaluation of Mchare and Matooke Bananas for Resistance to Fusarium oxysporum f. sp. cubense Race 1

“…It expands on the works of Arinaitwe et al (2019) [ 33 ], which found seven Mchare cultivars were susceptible to Foc race 1 in screen house evaluations, and the report of Kung’U and Jeffries (2001) [ 34 ] which found a Muraru cultivar in Kenya to be affected by Fusarium wilt. Kung’U and Jeffries (2001) [ 34 ] also showed Muraru to be less susceptible to Foc race 1 (VCGs 0124 and 01220) than Bluggoe and Gros Michel bananas [ 34 ]. The resistant diploid EAHB cultivars identified in the current study, therefore, are potentially useful replacements for the susceptible cultivars in the area.…”

“…Until recently, a limited amount of information was available on the response of diploid EAHB bananas to Foc race 1, despite the seasonal appearance of Fusarium wilt on Mchare and Muraru bananas in Tanzania and Kenya, respectively [ 33 , 34 ]. This lack of information delayed the management of banana Fusarium wilt in areas where losses occur, including efforts to improve EAHB diploids genetically for Fusarium wilt resistance.…”

“…Seven Mchare cultivars maintained at Kawanda in Uganda were found to be susceptible to Foc race 1 in a screen house evaluation [ 33 ], but there are no scientific reports of Fusarium wilt of Mchare bananas in the field in Uganda and Tanzania. The disease has, however, been reported on a close relative of Mchare bananas, the Muraru banana [ 34 ].…”

The development of a multiplex PCR assay for the detection of Fusarium oxysporum f. sp. cubense lineage VI strains in East and Central Africa

“…Triploid EAHB bananas (AAA), commonly known as Matoke bananas, are resistant to Foc Lineage VI strains (Kangire et al 2000;Tushemereirwe et al 2000). However, diploid bananas (AA) grown in some parts of Kenya (Onyango et al 2011), and known as Muraru bananas, are susceptible to Fusarium wilt (Kung'u and Jeffries 2001). The susceptibility of Mchare (AA) bananas grown in the Kilimanjaro region in Tanzania (De Langhe et al 2001) has not previously been reported.…”

“…Race classification has been used to distinguish among Foc strains, and is based on the pathogen's ability to cause disease to a differential set of banana cultivars. There are three Foc races; race 1, race 2 and race 4, causing disease to Gros Michel, Bluggoe and Cavendish cultivars, respectively (Stover 1962;Kung'u and Jeffries 2001;Ploetz 2006Ploetz , 2015a. The identification of Foc races is, however, not always reliable as some banana varieties are predisposed to infection by Foc in unfavourable environments (Ploetz 2015a).…”