Impeded spread of Tomato spotted wilt virus to pepper plants less preferred by Frankliniella occidentalis
Peters D, Maris P, N Joosten N, Goldbach RW
Laboratory of Virology, Wageningen Agricultural University, Binnenhaven 11, 6709 PD Wageningen, the Netherlands.
Correspondence: dick.peters@wur.nl
Among its many hosts, resistance to Tomato spotted wilt virus (TSWV) has been incorporated in a limited number of plant species, like groundnut, pepper and tomato. This resistance occurring in natural sources has been overcome by some TSWV isolates in pepper and tomato.. Artificial resistance has also been obtained by insertion of the N gene of TSWV or parts of this gene in some hosts, but has not widely been applied in the field. Not much attention has thus far been spent on the significance of resistance to the vector to control spread of TSWV. This may be due to the cumbersome screening techniques to be used and the likelihood that this resistance is polygenic. In addition, this resistance may have either antagonistic or synergistic effects on the spread of tospoviruses. In the former case this resistance may promote the spread of the virus when incoming thrips may search for new hosts after probing non-preferred hosts. In the latter case, the spread of the virus might become restricted when thrips do not migrate from a non-preferred host. To get answers on these questions the spread of TSWV among thrips-susceptible and thrips-resistant pepper plants, which were equally susceptible to TSWV, was studied. All plants of the accession Pikante Reuzen (susceptible to thrips) exposed to infectious adult Frankliniella occidentalis thrips became infected in non-choice tests, compared to only 40% of the plants of the more resistant accession CPRO-1. Infection of the resistant plants could be attributed to inoculation by the released thrips, but not to a secondary spread as the reproduction of thrips and larval survival was strongly impeded on these plants. More thrips-susceptible than -resistant plants became also infected when the thrips were released in a mixed stand. All resistant plants became finally infected probably due to secondary spread of virus from the infected susceptible plants. Further studies revealed that the behavior of thrips did not differ on leaves of the susceptible and resistant plants, although the thrips dispersed at a slightly higher rate from resistant plants. Thrips populations grew considerably faster on susceptible plants when they were released on resistant plants in a mixed stand, whereas only a few specimens were detected on resistant plants when released on susceptible plants. The results show evidently that resistance to thrips is a proper trait to impede the spread of tospoviruses as both primary and secondary infections become restricted due to a lower infection success, a lower acceptance rate of the plant by thrips and a decreased population development. (Maris PC et al. 2003. Phytopathology 93: 96¨C101; Maris PC et al. 2003. Phytopathology 93: 1223¨C1227; Maris PC et al. 2004. Entomologia Experimentalis et Applicata 113: 149¨C155).
