![]() Recently, the phytoplasma associated with frogskin has been cultured on artificial media from root phloem. Sometimes the cracks form a ring around the root. ![]() The roots are thin, woody, with thick outer layers, and deep cracks. An unusual disease in that there are few above ground symptoms, apart from slight swellings of lower stems, and curling and yellow/green patterns on leaves of some varieties. Cassava frogskin disease (South America, many countries).įirst reported in the early 1970s. ![]() Occasionally, stems show internal discolouration of the vascular tissues (Photo 5). The following are some examples: In cassava, a variety of symptoms are reported: yellowing of leaves, bunching of foliage due to shortening of internodes (the distances between leaves) (Photos 1&2), the development of normally-dormant shoots to produce so-called witches' brooms', (the broomstick of a flying witch!) (Photos 3&4), or only occasional leaf mosaic symptoms until harvest when plants showed rough skin, banding, cracking and woodiness in thin storage roots. They are typically associated with 'yellows' diseases. These bacteria-like, phloem-dwelling organisms, without rigid cell walls, have proved difficult to isolate and culture. Proof that phytoplasmas are involved is difficult to obtain. A number of diseases have emerged around the world that are associated with phytoplasmas.
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