- The effects of the inherent transmissibility of the
virus and of the inherent transmitting ability of aphids
on the transmission of bean yellow mosaic virus (BYMV)
were studied along with four virus-vector relationships of
BYMV and the green peach aphid, Myzus persicae (Sulz.).
In addition, investigations were made on the transmission
of clover yellow mosaic virus (CYMV) by aphids and on the
effects of temperature on the susceptibility of Lincoln
pea to inoculation with bean yellow mosaic virus (BYMV)
by M. persicae.
All eight aphid species included in these tests
transmitted BYMV. The aphids ranked in the order of
descending efficiency of BYMV transmission as follows:
Macrosiphum euphorbiae (Thos.), Benton Co. (Oregon)
clone of Acyrthosiphon pisum (Harris), Myzus persicae (Sulz.), Aphis fabae Scop., Columbia Co. (Washington)
clone of A. pisum, Macrosiphum rosae (L.), Therioaphis riehmi (Borner), Brachycaudus helichrysi (Kltb.) and Cavariella aegophodii (Scop.). Efficiency of transmission
varied from 62 percent to 7 percent. B. helichrysi, C. aegopodii and T. riehmi have not previously been reported
to transmit BYMV.
Collections of the pea aphid, Acyrthosiphon pisum
(Harris), from Oregon and Washington included biotypes
differing in BYMV transmission, fecundity, body size and
host preference. No differences were found among M.
BYMV isolates differed in symptom expression and in
the ease with which they were transmitted by aphids.
Aphid transmissibility of BYMV was lost or greatly reduced
following a single mechanical transfer. The vector-Iess isolate multiplied to the virtual exclusion of the
aphid transmissible isolate when broad bean plants were
inoculated simultaneously with both these isolates.
Different areas of broad bean leaves were not equal
as sources of BYMV for M. persicae. More aphids transmitted
the virus from the interveinal chlorotic area
than from the green areas along the veins. Post-inoculation temperature for 48-56 hours had a
considerable influence on Lincoln pea susceptibility to
BYMV infection by M. persicae inoculation. More plants
were infected at 27 and 30°C than at 15, 18 or 24°C.
Post-inoculation temperature treatment for 24 hours or
less did not have any appreciable effect. Pre-inoculation
temperature for 47-55 hours also considerably influenced
plant susceptibility to BYMV infection by aphid inoculation.
Twice as many plants were infected at 15°C as at
30°C. The effects of pre- and post-inoculation temperatures
were not additive. The number of plants infected
depended entirely on post-inoculation temperature.
Artificial termination of acquisition probes did not
have any appreciable effect on BYMV transmission by M.
persicae. No significant differences in virus transmission
were found for aphids with acquisition probes in the
11- to 45-second, range. Virus transmission increased
with an increase in the number of test probes. Loss of
BYMV by feeding M. persicae could be expressed exponentially.
Half-Iife of the retention of virus by feeding
aphids was about three minutes.
Clover yellow mosaic virus could be easily confused
with BYMV on the basis of symptom expression in Dwarf Horticultural and Bountiful cultivars of the bean, Phaseolus vulgaris L., Pisum sativum L. cv. Lincoln, Vicia faba L. (secondary symptoms, especially on new sprouts),
and in Chenopodium amaranticolor Coste and Reyn. (primary
reaction). It was not transmitted by A. pisum, A. fabae, C. aegopodii, M. euphorbiae, M. rosae and M. persicae.