Discovery: resistance to wheat dwarfing virus

If the wan­der­ing sand cica­da (Psam­motet­tix alienus) bites a wheat plant to drink plant sap, the con­se­quences can be fatal: Along with its sali­va, the cica­da can trans­mit Wheat Dwarf Virus (WDV). Depend­ing on the age of the plant at the time of infec­tion, yields drop by at least 30 per­cent, and even total fail­ure is pos­si­ble. Researchers at the Julius Kühn Insti­tute (JKI) have now test­ed 500 wheat vari­eties, includ­ing cul­ti­vars, genebank acces­sions and wild species, for their resis­tance to the virus. The wild vari­eties were found to be sim­i­lar­ly sus­cep­ti­ble to the virus as mod­ern vari­eties, sug­gest­ing that breed­ing has not result­ed in a loss of resis­tance genes.

More than half of the vari­eties stud­ied per­ished as a result of infec­tion. Two Hun­gar­i­an vari­eties described as resis­tant showed only some quan­ti­ta­tive resis­tance to the virus dis­ease, with infec­tion rates of 21.5 and 34.5 per­cent. How­ev­er, the researchers dis­cov­ered near-com­plete resis­tance in the Russ­ian win­ter wheat vari­ety “Fisht,” which was infect­ed at only 5.7 per­cent. They describe this in their recent pub­li­ca­tion in the open-access jour­nal Fron­tiers in Plant Science.

“For the first time, we were able to deter­mine QTL asso­ci­at­ed with low yield loss­es due to the virus. Using genet­ic mark­ers, these QTL could be crossed into elite wheat lines in the future to cre­ate resis­tant varieties.”

- Anne-Kathrin Pfrieme

QTL (quan­ti­ta­tive trait loci) are seg­ments in the genome that are asso­ci­at­ed with quan­ti­ta­tive traits — traits such as height, weight, or even dis­ease resis­tance. These grad­u­al­ly mea­sur­able traits are the result of the inter­ac­tion of dif­fer­ent genes. Of the 35 gene loci first iden­ti­fied, 14 remained after test­ing that could be con­sis­tent­ly linked to low yield loss­es from wheat wilt virus infections.

The inter­est of var­i­ous breed­ing com­pa­nies, which were involved in the research togeth­er with the Gesellschaft zur Förderung von Pflanzenin­no­va­tion e.V. (Soci­ety for the Pro­mo­tion of Plant Inno­va­tion), was high, he said, espe­cial­ly since the virus can­not be con­trolled and no plant pro­tec­tion prod­uct is approved with­in the EU against the cica­da that trans­mits it.

Background

Many cica­da and aphid species ben­e­fit from cli­mate change because high­er tem­per­a­tures allow them to remain active longer and, in some cas­es, pro­duce anoth­er gen­er­a­tion of off­spring. This has recent­ly been proven once again by a sur­vey using an insect suc­tion trap at the Quedlin­burg site. The region of west­ern Sax­ony-Anhalt is par­tic­u­lar­ly affect­ed by cli­mate change in the form of ris­ing tem­per­a­tures and drought. Virus dis­eases trans­mit­ted by these vec­tors are also on the increase.

The wheat dwarf­ing virus has spread through­out Europe since the mid­dle of the 20th cen­tu­ry. In addi­tion to wheat, it also infects bar­ley and oth­er cere­als. Today, it is one of the most impor­tant cere­al dis­eases in Europe, Asia and Africa. It is trans­mit­ted in the fall by adult wan­der­ing sand chirps (Psam­motet­tix alienus). Sec­ondary infec­tion by nymphs of the cica­da is pos­si­ble in spring. Infec­tion is man­i­fest­ed by striped col­or­ing of leaves, chloro­sis, reduced num­ber of ears, reduced win­ter har­di­ness, and death of plants at ear­ly stages of development.

Since virus­es can­not be con­trolled with plant pro­tec­tion prod­ucts and, in some cas­es, active sub­stances for envi­ron­men­tal­ly com­pat­i­ble use against the vec­tors are also lack­ing, the breed­ing of vari­eties that are resis­tant to the pathogens is becom­ing increas­ing­ly important.