VARIABILITY AMONG APHID CLONES OF RHOPALOSIPHUM PADI L. AND SITOBION AVENAE FABR. (HOMOPTERA: APHIDIDAE) IN TRANSMISSION OF THREE PAV ISOLATES OF BARLEY YELLOW DWARF VIRUSES

Abstract

The Canadian Entomologist 128: 199-207 (1996) Attack and emergence of the engraver beetles Ipspini Say and I. latidens LeConte were measured in lodgepole pine (Pinus contorta var. latifolia Engelm.) naturally attacked by the mountain pine beetle, Dendroctonusponderosae Hopk., in 1991. Sample trees were baited with the Ips pheromones ipsdienol and lanierone 1 week and 3 weeks after attack by the mountain pine beetle and again the following spring to observe the effects of the timing of bait placement. The densities of attack, egg gallery length, emergence, and hibernation of Ips species were measured. Ips latidens did not attack either the baited or unbaited trees at breast height until the spring of 1992 and the relatively low emergence was not significantly different by treatments. Among the 1991 treatments, the densities at breast height (1.3 m) of I. pini attack, egg gallery length, adult emergence in the fall of 1991, and numbers of hibernating adults in the duff were all highest for the 3-week treatment and lowest for the unbaited treatment. Significantly higher densities of beetles emerged and hibernated in the duff on the north sides of trees. Ipspini emergence in late summer 1992 from trees additionally baited in spring 1992 was significantly higher than for trees baited only in fall 1991. The density and temporal distribution of the emergence of both Ips species is discussed in relation to that of the mountain pine beetle. Safranyik, L., T.L. Shore et D.A. Linton. 1996. Augmentation des infestation et de la densite des couvees d'lps pini Say (Coleoptera: Scolytidae) aprks traitement i l'ipsdiknol et i la lanierone dans des pins vrilles deji infest& par le Dendroctone du pin ponderosa. The Canadian Entomologist 128: 199-207. THE CANADIAN ENTOMOLOGIST March/April1996

Role of acquisition and inoculation time in the expression of clonal variation for BYDV‐PAV transmission in the aphid species Rhopalosiphum padi

“…These results are consistent with those of Rochow & Eastop (1966) who found no significant difference between percentages of PAV (New York isolate) transmission by two clones originating from Illinois and Kansas, under similar experimental conditions (48 h AAP/ 120 h IAP at 21ЊC). Conversely, they conflict with those of Guo et al (1996), who found large differences in percentage of transmission of three PAV isolates (21-91%) among six clones collected in France. There are three possible causes of this discrepancy.…”

“…There are three possible causes of this discrepancy. First, no comparison was made between the clones and virus isolates used here and those used by Guo et al (1996), and PAV-4 could be more easily transmitted overall by R. padi than the isolates tested by these authors. Nevertheless, experiments on another PAV isolate (PAV-13, originating from H. Lapierre, INRA Station de Pathologie Végétale, Versailles France) with a 48 h AAP/120 h IAP, using 11 of the clones from our sample, gave transmission percentages of 90-100% (Sadeghi, unpublished data); this confirms results obtained with PAV-4.…”

“…Nevertheless, experiments on another PAV isolate (PAV-13, originating from H. Lapierre, INRA Station de Pathologie Végétale, Versailles France) with a 48 h AAP/120 h IAP, using 11 of the clones from our sample, gave transmission percentages of 90-100% (Sadeghi, unpublished data); this confirms results obtained with PAV-4. Second, the experimental conditions were different: our transmission tests were done entirely at 20ЊC with third instar nymphs whereas Guo et al (1996) did their acquisition tests at 14ЊC and inoculation tests at 25ЊC in a glasshouse and used adult aphids. Nevertheless, in a preliminary experiment at 15ЊC (Sadeghi, unpublished data) we found no differences among 16 clones of our sample for PAV-4 transmission.…”

“…In Europe, R. padi is considered as the main vector of BYDV-PAV because in autumn, on grasses and maize, it produces huge alate populations, which are likely to invade young cereal crops (Plumb, 1983;Leclercq-Le Quillec et al, 1995). Guo et al (1996) pointed out variations in BYDV-PAV transmission by six clones of R. padi collected in two areas of France.…”

Intra-specific variation and inheritance of BYDV-PAV transmission in the aphid Sitobion avenae

“…Inter-clonal variation in virus transmission by aphids has been reported for both stylet-borne (Sohi and Swenson 1964;Thottappilly et al, 1972;Jurik et al, 1980;Singh et al, 1983;Lupoli et al, 1992) and circulative viruses (Bjo¨rling and Ossiannilsson, 1958;Robert and Maury 1970;Guo et al, 1996Guo et al, , 1997a. In most cases, variations in the virus-transmitting abilities of different clones were detected.…”