Discovery of resistance-breaking chemistries for varroa mite management

In Arabidopsis thaliana Columbia (Col-0) plants, the restriction of Tobacco etch virus (TEV) long-distance movement involves at least three dominant RTM (restricted TEV movement) genes named RTM1, RTM2, and RTM3. Previous work has established that, while the RTM-mediated resistance is also effective against other potyviruses, such as Plum pox virus (PPV) and Lettuce mosaic virus (LMV), some isolates of these viruses are able to overcome the RTM mechanism. In order to identify the viral determinant of this RTM-resistance breaking, the biological properties of recombinants between PPV-R, which systemically infects Col-0, and PPV-PSes, restricted by the RTM resistance, were evaluated. Recombinants that contain the PPV-R coat protein (CP) sequence in an RTM-restricted background are able to systemically infect Col-0. The use of recombinants carrying chimeric CP genes indicated that one or more PPV resistance-breaking determinants map to the 5′ half of the CP gene. In the case of LMV, sequencing of independent RTM-breaking variants recovered after serial passages of the LMV AF199 isolate on Col-0 plants revealed, in each case, amino acid changes in the CP N-terminal region, close to the DAG motif. Taken together, these findings demonstrate that the potyvirus CP N-terminal region determines the outcome of the interaction with the RTM-mediated resistance.

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Independent Resistant Reactions Expressed in Root and Tuber of Potato Breeding Lines with Introgressed Resistance to Meloidogyne chitwoodi

Phytopathology ◽

10.1094/phyto-99-9-1085 ◽

2009 ◽

Vol 99 (9) ◽

pp. 1085-1089 ◽

Cited By ~ 22

Author(s):

C. R. Brown ◽

H. Mojtahedi ◽

L.-H. Zhang ◽

E. Riga

Keyword(s):

Genetic Factors ◽

Dominant Gene ◽

Breeding Line ◽

Single Dominant Gene ◽

Solanum Bulbocastanum ◽

Chromosome 11 ◽

Meloidogyne Chitwoodi ◽

Tuber Resistance ◽

Advanced Backcross ◽

Resistance Breaking

Resistance to Meloidogyne chitwoodi was introgressed from Solanum bulbocastanum into the cultivated gene pool of potato. A single dominant gene is responsible for resistance to race 1 reproduction on the root system. An additional form of resistance was discovered in certain advanced backcross clones. A BC5 clone, PA99N82-4, resisted invasion of tubers by available nematode juveniles whether supplied by weeds or challenged by several root resistance-breaking pathotypes. This tuber resistance is inherited as a single dominant gene and is linked to RMc1(blb). Because this gene has been mapped to chromosome 11, tuber resistance genetic factors are inferred to be on the same chromosome in coupling phase. Among 153 progeny derived from crosses with PA99N82-4, 42 recombinants, comprising both resistant root/susceptible tuber and susceptible root/resistant tubers, were found while other progeny were doubly resistant (like PA99N82-4) or doubly susceptible. Therefore, the existence of two linked genetic factors controlling independently expressed traits is confirmed. The combination of the two phenotypes is likely to be a sufficient level of resistance to avoid tuber damage from circumstances that provide exogenous juveniles proximal to the tubers in the soil. These factors are weed hosts of M. chitwoodi host races and pathotypes of M. chitwoodi that overcome RMc1(blb). Under field conditions, where a resistance-breaking pathotype of M. chitwoodi was present, tuber-resistant PA99N82-4 breeding line produced tubers which were commercially acceptable and not culled. A related breeding line, root resistant but tuber susceptible, and Russet Burbank were severely tuber damaged and commercially unacceptable.

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Ecological characteristics of Varroa destructor (parasitiformes, varroidea) and its environmental capacity as a key factor for development of varroosis panzootia

Vestnik Zoologii ◽

10.2478/v10058-012-0034-9 ◽

2012 ◽

Vol 46 (5) ◽

pp. 8-14

Author(s):

I. A. Akimov ◽

O. P. Korzh

Keyword(s):

Life Cycle ◽

Honey Bee ◽

Host Species ◽

Varroa Destructor ◽

Varroa Mite ◽

Environmental Capacity ◽

Ecological Characteristics ◽

High Pathogenicity ◽

Key Factor

Ecological Characteristics of Varroa destructor (Parasitiformes, Varroidae) and Its Environmental Capacity as a Key Factor for Development of Varroosis Panzootia. Akimov I. A., Korzh O. P. - By means of formalized schematic models of relationship with hosts the varroa mite uniqueness as a parasite is shown. The life cycle of this species requires the change of a host species at different stages of their development and physiological states. Thus the mite parasitizes not only a separate bee but a whole hive. The fact that the whole hive but not a single bee dies during varroosis development supports this idea. The impetus for this type of parasitism is the relative constancy of the environment in the hive supported by bees even in winter. Exactly this fact causes high pathogenicity of the varroa for the honey bee and its control complexity.

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