Journal article Open Access
Сassava’s productivity in Madagascar is affected by pests and diseases, among which the whitefly Bemisia tabaci (Gennadius) transmitting cassava mosaic begomoviruses (CMBs) is most important. The present study sought to establish the abundance and diversity of B. tabaci cryptic species on cassava and other host plants in Madagascar. In addition, cassava mosaic disease (CMD) incidence and symptom severity were assessed. The identity and genetic diversity of B. tabaci samples collected on cassava and other plant species in Central Highlands and Tsaratanana Massif in northwestern region were studied using the partial mitochondrial cytochrome oxidase I (mtCOI) gene. The analyses of the mtCOI sequences revealed three B. tabaci cryptic species—Sub-Saharan Africa 1 (SSA1), Mediterranean (MED) and the Indian Ocean (IO)—in the sampled areas. SSA1 was the dominant cryptic species, with 100 % occurrence on cassava crops. For the first time, we report the occurrence of MED in Madagascar. Both MED and IO, the indigenous species in the South West Indian Ocean islands of Anajouan Mayotte, Grande Comore, Mauritius, Reunion, Seychelles and Madagascar, occurred on non-cassava hosts. As opposed to previous reports, we recorded no B. tabaci Middle East Asia Minor 1 – MEAM1 cryptic species (formerly also known as the B-biotype) on any of the sampled plants and locations. Generally, the abundance of adult whiteflies was low (<1 specimen per plant) on cassava in all the sampled locations, except in Analavory (3.93) and Ampitolova (3.00) in Central Highlands. Similarly, the whitefly abundance was low on the non-cassava plant species, likely hosts for B. tabaci IO and MED. Cassava mosaic disease was observed in 100 % of the surveyed cassava fields. The disease symptoms were generally mild, with severities of 2.00–3.13 (average, 2.62). Locations differed significantly (P<0.001, LSD=5.00) in CMD incidences. The CMD incidence ranged between 30–100 % (averaged ca 59 %). Our findings provide current knowledge of the economically important B. tabaci species, which is vital to the development of sustainable management practices for the vector and cassava viral diseases in Madagascar.