Efficacy of chemotherapy and thermotherapy in elimination of East African cassava mosaic virus from Tanzanian cassava landrace.

Christina Edward Kidulile,Elijah Miinda Ateka,Joseph Canisius Ndunguru,Amos Emitati Alakonya

doi:10.1111/jph.12725

Abstract

Cassava mosaic disease is caused by cassava mosaic begomoviruses (CMBs) and can result in crop losses up to 100% in cassava (Manihot esculenta) in Tanzania. We investigated the efficacy of chemotherapy and thermotherapy for elimination of East African cassava mosaic virus (EACMV) of Tanzanian cassava. In vitro plantlets from EACMV‐infected plants obtained from coastal Tanzania were established in the greenhouse. Leaves were sampled from the plants and tested to confirm the presence of EACMV. Plantlets of plants positive for EACMV were initiated in Murashige and Skoog (MS) medium. On the second subculture, they were subjected into chemical treatment in the medium containing salicylic acid (0, 10, 20, 30 and 40 mg/L) and ribavirin (0, 5, 10, 15 and 20 mg/L). In the second experiment, EACMV‐infected plantlets were subjected to temperatures between 35 and 40°C with 28°C as the control. After 42 days of growth, DNA was extracted from plant leaves and PCR amplification was performed using EACMV specific primers. It was found that plant survival decreased with increasing levels of both salicylic acid and ribavirin concentrations. In general, plants treated with salicylic acid exhibited a lower plant survival % than those treated with ribavirin. However, the percentage of virus‐free plants increased with an increase in the concentration of both ribavirin and salicylic acid. The most effective concentrations were 20 mg/L of ribavirin and 30 mg/L of salicylic acid; these resulted in 85.0% and 88.9% virus‐free plantlets, respectively. With regard to thermotherapy, 35°C resulted in 79.5% virus‐free plantlets compared to 69.5% at 40°C. Based on virus elimination, ribavirin at 20 mg/L, salicylic acid 30 mg/L and thermotherapy at 35°C are recommended for production of EACMV free cassava plantlets from infected cassava landraces.

Highlights

Cassava (Manihot esculenta) is a major staple food crop in sub- Saharan Africa (SSA) where it accounts for 176 million metric tons of the 270 million metric tons of annual global production (FAO, 2014)
cassava mosaic disease (CMD) is caused by at least nine species of cassava mosaic begomoviruses (CMBs) that can be broadly categorized as African cassava mosaic viruses (ACMVs) and East African cassava mosaic viruses (EACMVs)
The aim of this study was to evaluate the effectiveness of chemotherapy and thermotherapy in eliminating EACMV in widely grown, farmer-preferred cassava landraces in Tanzania

Summary

Introduction

Cassava (Manihot esculenta) is a major staple food crop in sub- Saharan Africa (SSA) where it accounts for 176 million metric tons of the 270 million metric tons of annual global production (FAO, 2014). Despite its important role in alleviating food security, there has been a low productivity of cassava per unit area in SSA (Nweke, Spencer, & Lynam, 2002). This has mainly occurred due to the impact of viral. CMD is caused by at least nine species of cassava mosaic begomoviruses (CMBs) that can be broadly categorized as African cassava mosaic viruses (ACMVs) and East African cassava mosaic viruses (EACMVs) These viruses are transmitted by whiteflies (Bemisia tabaci Gennadius) and spread through infected planting materials and contaminated implements, and their existence can cause yield losses of up to 100% on susceptible genotypes (Varma & Malathi, 2003). These methods can be used alone or in combination with other methods to obtain virus-free plantlets (Paprstein et al, 2008)

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