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Plantwise Technical Factsheet

mild mottle of sweet potato (Sweet potato mild mottle virus)

Host plants / species affected
Ipomoea batatas (sweet potato)
List of symptoms/signs
Leaves  -  abnormal patterns
Whole plant  -  dwarfing
Symptoms
In sweet potato, its only known natural host, SPMMV causes mild leaf mottling and stunting in plants of intolerant cultivars, but less severe symptoms or even symtomless infection in those of tolerant genotypes; some cultivars are apparently immune (Hollings et al., 1976a, b). However, SPMMV sometimes occurs in sweet potatoes together with other viruses; plants also containing sweet potato feathery mottle potyvirus and/or sweet potato sunken vein closterovirus often have severely chlorotic and distorted leaves and are severely stunted (Cohen et al., 1992; Winter et al., 1992; Hoyer et al., 1996).

Prevention and control
To minimize SPMMV-induced crop losses, it is often essential to grow virus-tested stocks; in cultivars that are totally infected, these can be obtained by meristem-tip culture followed by multiplication and eventual commercial use of plants in which no virus can be detected under insect-proof conditions. Methods for meristem-tip culture, either alone or combined with thermo- and/or chemotherapy, have been well described (Frison and Ng, 1981; Love et al., 1989; F Wambugu, University of Bath, Bath, personal communication, 1991). Levels of natural infection in parts of Uganda are often unusually low; under such circumstances, it is possible to simply select disease-free cuttings for subsequent planting (Gibson et al., 1997).

There is currently great interest in the possibility of producing virus-resistant transgenic plants, although none is yet available for sweet potato production (F Wambugu, University of Bath, Bath, personal communication, 1991).
Impact
Although its effect on yield has not been quantified, SPMMV alone probably has a significant deleterious effect on intolerant cultivars; however, together with sweet potato feathery mottle potyvirus and or sweet potato sunken vein closterovirus (Cohen et al., 1992; Winter et al., 1992; F Wambugu, University of Bath, Bath, personal communication, 1991), it has a very severe effect on plants.

Related treatment support
 
External factsheets
Sweetpotato DiagNotes Fact Sheets, The University of Queensland, English language
Sweetpotato DiagNotes Fact Sheets, The University of Queensland, English language
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