Green peach aphids, Myzus persicae (Sulz.) (Hemiptera: Aphididae), obtained from pepper fields, were colonized on susceptible pepper plants in a growth chamber. The development, survivorship, and life table parameters of the green peach aphid were evaluated on nine peppers cultivars as follows: Almuden, Bilano, Bird, Cabezo, de la Sierra, Eppo, Jaen, Raza, and Yatasto at controlled conditions (20 ± 1°C; about 70% RH; 14h photophase). The development times of immatures ranged from 6.1 days on Yatasto to 11.4 days on Jaen, whereas immature survival was close to 100% on all cultivars. The intrinsic rate of increase (r m ) for green peach aphid on Bilano and Yatasto were the highest. Jackknife estimates of r m varied from 0.281 to 0.174 females/female/day on Yatasto and Jaen, respectively. The mean population generation times (T) on these hosts ranged from 13.7 to 22.7 days. The highest net reproductive rates (R 0 ) were on Bird and Bilano (63.8 and 62.89 females/female/generation, respectively) and the lowest on De la Sierra and Almuden (34.1 and 38.7, respectively). Because of the high coefficient of determination (R (2)) values in Gompertz and Weibul models, survival data from different cultivars had a good fit to both models. The results pointed Jaen, Almuden, and Raza cultivars as the least suitable host plants, indicating that they were the most resistant to M. persicae among the cultivars we tested.

Greenbug and Russian wheat aphid (RWA) are two devastating pests of wheat. The first has a long history of new biotype emergence and recently. RWA resistance has just started to break down. Thus, it is necessary to find new sources of resistance that will broaden the genetic base against these pests in wheat. Seventy‐five doubled haploid recombinant (DHR) lines for chromosome 6A from the F1 of the cross between “Chinese Spring’ and the “Chinese Spring (Synthetic 6A) (Triticum dicoccoides × Aegilops tauschii)” substitution line were used as a mapping population for testing resistance to greenbug biotype C and to a new strain of RWA that appeared in Argentina in 2003. A quantitative trait locus (QTL) (br antixenosis to greenbug was significantly associated with the marker loci Xgwm1009 and Xgwm1185 located in the centromere region of chromosome 6A. Another QTL which accounted for most of the antixenosis against RWA was associated with the marker loci Xgwm1291 and Xiinni1150. both located on the long arm of chromosome 6A. This is the first report of greenbug and RWA resistance genes located on chromosome 6A. It is also the first report of antixenosis against the new strain of RWA. As most of the RWA resistance genes present in released cultivars have been located in [he D‐genome, it is highly desirable to find new sources in other genomes to combine the existing resistance genes with new sources.

Diuraphis noxia (Russian wheat aphid, RWA), one of the most aggressive pests of wheat, has evolved several biotypes with virulence matching known Dn resistance genes. This paper was aimed at determining the location of plant-defence genes triggered by RWA in a set of doubled haploid (DH) lines obtained from the cross of winter wheat varieties ‘Spark’ and ‘Rialto’. Both parental lines, 110 DH and CItr2401 (a RWA-resistant line) were screened for antixenosis, tolerance and antibiotic mechanisms of resistance with a population of RWA collected in Argentina. Antixenosis was not significantly linked to any marker locus. Tolerance traits showed significant associations with several chromosomes. Quantitative trait loci (QTL) for the foliar area developed during infestation was significantly associated with marker loci Xpsp3103 on 4DS, and Xgdm3 on 5DS. QTL for chlorophyll content in the infested plants were significantly associated with the marker loci Xgwm533 on 3BS and Xpsp3094 on 7AL, and a QTL for the number of expanded leaves was associated with the marker loci Xwmc264 on 3AS and XwPt8836 on 4DS. QTL for most of the tolerance traits were significantly associated with the same chromosome intervals on chromosomes 4DS and 5DS. The 4DS QTL were linked to or had a pleiotropic effect on Rht-D1. Most of the antibiosis traits were significantly associated with the same marker loci on chromosomes 4A (XwPt7405), 1B (XwPt9032) and 5B (Xbarc109 and Xbarc74). Several novel genes conferring tolerance and antibiosis to RWA were identified and these could be transferred into wheat cultivars to enlarge the genetic base of defence against this aphid pest. These new genes can be designated as QDn.unlp genes, following the rules for gene nomenclature in wheat.

No abstract

A collection of 26 cultivars of wheat Triticum aestivum were screened for resistance against the two main aphid pests of cereals, the greenbug Schizaphis graminum Rond. and the Russian wheat aphid (RWA) Diuraphis noxia Mordvilko. Since genetic variability has been found in Argentinean populations of both aphid species, this work was aimed at determining the response of different types of resistance in wheat cultivars when infested with aphids. Antixenosis, antibiosis and tolerance were evaluated with traditional tests in controlled environmental conditions using a clone of greenbug biotype C and a clone of RWA collected on wheat. Genetic resistance was found against one or both aphid species in several wheats. Most of the highest levels of antixenosis, antibiosis and tolerance against the two aphids occurred in different cultivars; as a consequence the resistance mechanisms for both pests appear to be partly independent. Antibiosis against greenbug or RWA appears to be determined by two different sets of genes, one affecting development time and the other reducing fecundity and longevity. The antibiosis against both aphid species in terms of their development time and the intrinsic rate of population increase resulted in a partial cross effect of these aphid traits against the alternative insect species. Nonetheless, the same cultivars affected the total fertility and the longevity of both aphids. Since the highest plant performance levels and the least plant damage were recorded in different wheats, different patterns of tolerance were displayed against the greenbug and the RWA. Consequently, different genes appear to be involved in several traits of the resistance mechanisms against the two aphids. The genes that independently conferred resistance to aphids could be combined in new cultivars of wheat to broaden their genetic base of resistance against the greenbug and the RWA.