Epidemiology of Blackberry chlorotic ringspot virus

The pollen- and seed-borne ilarviruses pose a substantial threat to many specialty crops, including berries, rose, and tree fruit, because there are no efficient control measures other than avoidance. The case of Blackberry chlorotic ringspot virus (BCRV) is of particular interest because the virus has been found to be an integral part of blackberry yellow vein disease and is widespread in rose plants affected by rose rosette disease. This study provides insight into the epidemiology of BCRV, including incidence in blackberry and rose; host range, with the addition of apple as a host of the virus; and seed transmission that exceeded 50% in rose. Sensitive detection protocols that can be used to avoid dissemination of infected material through nurseries and breeding programs were also developed.

Epidemiology of Blackberry yellow vein associated virus

Blackberry yellow vein disease is one of the most important diseases of blackberry in the United States. Several viruses are found associated with the symptomology but Blackberry yellow vein associated virus (BYVaV) appears to be the most prevalent of all, leading to the need for a better understanding of its epidemiology. Efficient detection protocols were developed using end-point and quantitative reverse-transcription polymerase chain reaction. A multi-state survey was performed on wild and cultivated blackberry to assess the geographical distribution of the virus. Two whitefly species, Trialeurodes abutilonea and T. vaporariorum, were identified as vectors and 25 plant species were tested as potential BYVaV hosts. The information obtained in this study can be used at multiple levels to better understand and control blackberry yellow vein disease.

Viral Interactions Lead to Decline of Blackberry Plants

Blackberry yellow vein disease (BYVD) poses a new threat to the blackberry industry in the United States. Blackberry yellow vein associated virus (BYVaV) was originally thought to be the sole cause of this disease. However, BYVaV has been found in several asymptomatic blackberry cultivars. An unusual member of the family Potyviridae was identified recently from symptomatic plants and named Blackberry virus Y (BVY). BVY has been shown to spread in the field and cause BYVD when co-infected with BYVaV. Both viruses are asymptomatic in single infections but are readily detectable in asymptomatic plants by reverse transcription–polymerase chain reaction (RT-PCR). However, in mixed infections, the titer of BYVaV is repressed, sometimes to levels undetectable by RT-PCR, while the concentration of BVY is increased several fold. Electron microscopy revealed a variety of viral inclusions in symptomatic leaf samples, but none could be found in single infections with either BVY or BYVaV. Although BYVaV has been consistently associated with BYVD in different geographical regions, the detection of BVY has thus far been restricted to northwest Arkansas. It has been hypothesized that BYVaV is the synergistic determinant of BYVD that causes symptoms in different cultivars at various locations during co-infection with other viruses.