Further studies on a British form of pea early‐browning virus

Abstract

SUMMARYAn isolate of pea early‐browning virus from Britain (PEBV (B)) has tubular particles most of which are either about 103 or 212 mμ long with sedimentation coefficients of 210 and 286 S respectively. Both types show cross‐banding at intervals of 2.5 mμ. Virus preparations containing only the shorter particles were not infective.PEBV (B) was transmitted to pea seedlings by both adult and juvenile Trichodorus primitivus (de Man) (Nematoda) and persisted for 32 days in T. primitivus kept without plants. In two experiments T. primitivus failed to transmit a Dutch isolate (PEBV (D)), which is distantly related serologically to PEBV (B). PEBV (B) was transmitted by nematodes to cucumber roots more readily in soil at 20d̀ than at 24d̀ C., and more readily at 24d̀ than at 29d̀ C.When transmitted by inoculation of sap, PEBV (B) and PEBV (D) caused similar symptoms in some pea varieties but differed in virulence towards others. Thirty‐one varieties resistant to natural infection with PEBV in The Netherlands were susceptible to PEBV (B) when manually inoculated with sap or when grown in naturally infested soil from one site; twenty‐six of these varieties did not become infected in soil from a second site, in which several other varieties that are susceptible in The Netherlands were infected. Varieties should therefore be tested for resistance by growing them on many infested fields. All but one of the pea varieties resistant to PEBV in The Netherlands became infected with the English form of tomato black ring virus when grown in soil containing infective Longidorus attenuatus Hooper.