Wheat Antixenosis, Antibiosis, and Tolerance to Infestation by <I>Delphacodes kuscheli</I> (Hemiptera: Delphacidae), a Vector of “Mal de Río Cuarto” in Argentina

Abstract

"Mal de Rio Cuarto", is the most important virus disease of corn, Zea mays L., in Argentina. It is caused by the Mal de Rio Cuarto virus (family Reoviridae, genus Fijivirus. MRCV), which is a persistent virus transmitted by Delphacodes kuscheli (Fennah 1955) (Hemiptera: Delphacidae). Because corn is not a natural host of D. kuscheli, it has little protection from this pest. In contrast, wheat, Triticum aestivum L., is one of the main hosts of this vector and a reservoir of MRCV. The aim of this work was to identify genes involved in antixenosis, antibiosis, and tolerance of infestation by D. kuscheli in wheat, which might be used to reduce the population level of this vector on corn. A set of recombinant dihaploid (RDH) lines for chromosome 6A derived from the F1 cross between 'Chinese Spring' (CS) X 'Chinese Spring (Synthetic 6A)' (S6A) substitution line, was used for mapping. The S6A parental line is resistant to the MRCV vector. Antixenosis, antibiosis, and tolerance were evaluated using conventional tests in controlled environmental conditions. Most of the RDH and S6A showed higher levels of antixenosis against D. kuscheli than the parental line CS. The RDH lines showed highly significant antibiosis in terms of the duration of first, third, and fifth nymphal instars, developmental time (days), survival and fecundity. There were highly significant differences in the tolerance to D. kuscheli based on the chlorophyll content of the first and second leaves, foliar area, and aboveground fresh and dry weights. The duration of the fifth nymphal instar and the developmental period were significantly associated with Xgwm1017 marker loci, located at 48 cM on 6AL. Another quantitative trait locus accounting for the variation in chlorophyll content of the first leaf was associated with the interval between loci Xgwm459 and Xgwm334a, located in the telomeric region of the 6AS chromosome arm. The alleles with positive effects came from S6A. Antibiotic resistance of RDH could be useful for controlling the population increase of the MRCV vector on wheat, because prolonging the duration of development increases the period between two subsequent generations, so reducing the abundance of infective populations colonizing corn.