Apple mosaic virus

The most efficient way to manage the disease is through preventative measures and avoid planting contaminated material.[1] Since these viruses cannot be directly removed from the plant itself, the most practical technique to manage ApMV is to plant certified trees obtained from Plant Improvement Organizations .[2] Because ApMV can be asymptomatic for quite a while, it is also best to test for the pathogen using high sensitivity and high specificity detection methods such as ELISA.[1]

Various other techniques have been utilized to eliminate the virus from diseased plant species. A common technique used in the past is thermotherapy.[1] Since many viruses are sensitive to elevated temperatures, utilizing heat treatment in a controlled growth chamber will deplete the symptoms for the following years.[1] A study by Hunter et al. 1959 was conducted, where buds from virus infected trees were grafted onto healthy trees. The healthy trees with the buds were then incubated at 37 °C for 28, 30, 36 and 40 days. A year following the incubation, there were no symptoms present on the healthy tree other than from the buds.[9] However, a potential drawback to this study was that the plants were not tested for more than a year, and sometimes symptoms can take up to two years to develop.[1] Other studies have also reported similar results. Another study conducted by Pandey et al. (1972) suggested that plant exposure to temperatures of 40 degrees Celsius or 50 degrees Celsius for, respectively, 30 and 15 minutes were successful in inactivating ApMV. This inactivation was ultimately tested by the ELISA detection method.[1] On the contrary, lower temperatures and low heat durations have commonly failed to inactivate the virus.[1][10]

Another method that has been tested is cross protection. Cross protection is a type of induced resistance that is developed among plants against viruses.[11] During this event, a prior infection with one virus may offer protection against another closely related viruses.[11] This technique has been tested on Johnathon apples. Healthy strains of the Johnathon apples were infected with a mild strain of ApMV and then further exposed to viral infections by moderate and severe strains.[11] The trees infected with the mild strains were found to be resistant by further attack of the virus.[11] As it can be seen, cross protection provides a control technique for mild strains of ApMV.

All in all, as stated above, the best way to manage ApMV is through prevention. Utilizing sterile equipment and plant certified trees are the most efficient ways to get ApMV free crops. Other methods such as thermotherapy and cross protection have also been used in the past.[12]

ApMV infects crops from all around the world including Denmark, Turkey, South Africa, New Zealand, England, Germany, Canada, Italy, Spain and the United States, including as far north as Alaska.[13][7][4]

ApMV prefers areas where there is a clear distinction between the spring and summer seasons.[14] Most samples of plants are commonly collected in the spring time for molecular determination of ApMV using ELISA. This is vital because concentration of ApMV is highly varied from season to season.[2] ApMV is known to be a labile virus because its concentrations are negatively affected by high temperatures.[1] In a study completed by Svoboda and Polák, they observed five symptomless apple trees infected with ApMV. These five symptomless trees were selected from a pool of 472 apple trees that were inoculated with ApMV in two different orchards. Samples of various plant tissue from young leaves, flower petal, dormant buds, and phloem were taken at different time of the vegetation period. In this study, ELISA was used to detect ApMV in the different samples from the five apple trees. The relative concentrations of the virus in the leaves and flower were highest in the earlier spring months such as March and April.[14] This suggests that the virus propagates better when it is under colder weather conditions.[14] Furthermore, during cooler months, the virus's relative concentration is highest in the leaf and flower, rather than the phloem and dormant bud. Once May and June occur, the relative concentrations of the disease severely decreases. This was evident by Svoboda and Polák's study because as the temperature rose from spring to summer, the ELISA test detected lower relative concentrations of ApMV.[14] As a result of this heat sensitivity, symptoms of ApMV tend to be masked in the summer months versus the spring months.[1][15]

• ICTVdB—The Universal Virus Database: Apple mosaic virus
• Family Groups—The Baltimore Method