COMPARISON OF THE EFFICIENCY OF VARIOUS W AYS OF TRANSFER OF POTATO-VIRUS-M (PVM)

At the end of the 1980s potato virus M - PVM was spread very fast in t he breeding and propagation material of some varieties (e.g. Sarka). F or these reasons the causes of this situation were sought for mainly i n the sphere of transfer of the virus. The possibility of artificial m echanical PVM transfer has been studied by suspension of virus through injured spouts in the period of pre-spring classification of tubers a nd at mechanized planting in the planter, followed by mechanical trans fer during growing season from the source of infection to healthy plan ts in replicated going through the row (imitation of negative selectio ns) and finally, by replicated so-called birching of healthy plants by foliage of plants infected with PVM. In view of spreading of PVM the effect of thin row spacing 75 x 60 cm was studied in three varieties. Field provocative trials with intentional planting of sources of infec tion and the method of grafting of tubers for PVM transfer were used. PVM diagnosis was carried out in air trials in post-harvest examinatio n added by the ELISA method. In trials with mechanical infection of sp routs, the Radka variety, with PVM - the highest range of infection wa s found in the variant with infection on the cut though the sprout (3. 4 and 5.2 %), double infection of injured sprouts (3.2 and 1.2 %). In other variants the range of infection did not exceed 2.3 %. These resu lts document a low degree of spreading the PVM by artificial infection of injured sprouts. Neither in the mechanical transfer in plants duri ng the growing season a strong spreading of PVM from the infections so urce was not recorded in tested variants - the range of infection foll owing the testing by ELISA method was 2.3 to 4.9 %. The lowest virus o ccurrence was in the variant where healthy plants were five times birc hed during the growing season by the foliage of plants infested with P VM. In comparing the degree of transfer of PVM through vectors in plot s with a thin spacing (75 x 60 cm) and normal one (75 x 30 cm), a high er occurrence of infection in thin spacing is manifested almost unambi guous. The transfer through vectors is significantly more important co mpared to mechanical ways of infection and participates much more in s preading of this virus. The PVM transfer by drafting of tubers by cock borer in the Karin variety was successful for 63 % when tested during post-harvest test + ELISA (for 45 % in plants from drafted tubers tes ted during the growing season). The natural transfer in field provocat ive conditions (close to the row with 100 % PVM infection) achieved 29 .6 % of infected tubers in post-harvest ELISA test. The conclusion of the study is the finding that PVM transfer exclusively by mechanical w ay so in sprouts, as in plants is not high and itself could not be the reason for the fast increase in the range of PVM infection in breedin g and plant propagation. The reasons has to be found in weak symptomat ic expression of PVM disease in plants, in not knowing the susceptibil ity of new varieties particularly to this virus, in increase of the fr equency of infection sources and intensive transfer of viruses by vect ors.