Viral diseases of cacti (Cactaceae Juss.)

Abstract

There are about 220 genera and 3000 species in Cactaceae family. Since its discovery in XV cacti gained much popularity among botanists, gardeners and collectors because of unusual and highly decorative appearance. Cactus viruses are known for about a century now. The first definitive indication came in 1951 in Europe. Currently, 13 viruses are known to infect plants of Cactaceae family: five members of the genus Potexvirus (CVX, OpVX, SchVX, ZyVX and PiVX), four members of the genus Tobamovirus (SOV, TMV, CMMoV and RCNaV), one representative of the Carlavirus (CV-2), one representative of the Carmovirus (SgCV) and two representatives of the genus Tospovirus (TSWV and INSV). Potexviruses are best described among the viruses infecting Cactaceous plants. Some infections are mostly symptomless, when others demonstrate both external and internal symptoms. Externally symptoms include chlorotic rings and spots on the pads of Opuntia sp., reddening of the fronds of the Zygocactus sp., etc. Occasionally more severe symptoms, such as bending, marked yellowing and dieback of stems occur. The article discusses the viruses infecting Cactaceae family members, their biological characteristics, geographical distribution and history of their discovery. It covers the problem of genetic differentiation between some Asian and European isolates of potexviruses, and describes peculiarities of mono- and co-infections in different species of cacti. The article also considers the practical value of cacti for the gardening and exemplifies the use of their biologically active substances in medicine and pharmaceutical industry. Viral infections can damage cacti rendering raw material inapplicable for practical use. Hence it is necessary to apply not only technical protective measures, but also timely application of modern methods of diagnosis and the establishment of diversity of viruses circulating in the collections.