Evidence for regional diversity and host adaptation in Iranian populations of the Russian wheat aphid

Abstract

Effective pest management is greatly facilitated by knowledge of the genetic structure and host adaptation of the pest species in question. The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) (Homoptera: Aphididae: Macrosiphini), is an important economic pest in many cereal-growing areas of the world, and in this study we investigated these aspects of its populations, using microsatellite markers and host plant response assays. Diuraphis noxia was sampled from 38 locations in Iran and genotyped at four polymorphic microsatellite loci that had been isolated from various Sitobion species. We identified 50 multilocus genotypes in 376 individuals. The overall observed heterozygosity was 0.134. F-statistics showed a regional partitioning in D. noxia populations with overall F ST = 0.231. In addition, there was a significant correlation between genetic and geographic distances. In order to test for the ecological consequences of genetic variability in D. noxia , biotypic variation amongst the isolates collected from wheat ( Triticum aestivum L.) and barley ( Hordeum vulgare L.) was evaluated on a number of resistant and susceptible wheat varieties. The plant variables we measured were damage rating (based on leaf chlorosis, leaf rolling, wilting, and death of the host plant), host plant dry weight, and root length. Damage rating was the best criterion for detecting biotypic variation in D. noxia . Discriminant analysis correctly classified the isolates in respective groups in 80 -91.8% of the cases. The barley isolate showed no differences in performance on resistant and susceptible wheat, indicating a lack of gene-by-gene relationship with wheat plants. In contrast, wheat isolates differentially damaged the resistant and susceptible plants and showed moderate to severe virulence.

Limited Genetic Variation Within and Between Russian Wheat Aphid (Hemiptera: Aphididae) Biotypes in the United States

“…Allele sizes are shown in Table 2. Our results differ than those of Dolatti et al (2005). They found Iranian populations to be polymorphic for Sm11, S16b, S23, and Sa4.⌺.…”

“…Eight SSR loci were evaluated for variation within and between biotypes using primer pairs capable of cross species ampliÞcation; Sm10, Sm11, Sm12, S16b, S17b, S23, S49, and Sa4.⌺ (Simon et al 1999;Wilson et al 2004). Although cloned from other aphid species, these primers were shown to amplify D. noxia DNA and detect polymorphisms in Iranian populations (Wilson et al 2004;Dolatti et al 2005). PCR reactions were carried out in 10-l volumes by using Colorless GoTaq Flexi Buffer (Promega).…”

Differential invasion success among biotypes: case of Bemisia tabaci

“…Biotypic variations within species have been extensively described in whiteflies and aphids. Biotypic variation has been related to insecticide resistance (Horowitz et al 2005), host range (Dolatti et al 2005;Hebert et al 2006), plant physiological disorders induced by the insect (Yokomi et al 1990) or differential fitness (Jyoti and Michaud 2005). These differences tend to persist when several biotypes are brought in sympatry, suggesting at least partial reproductive isolation among them; however the exact degree of isolation is usually unknown (Diehl and Bush 1984).…”

Comparison of categories of resistance in wheat and barley genotypes against biotype 2 of the Russian wheat aphid, Diuraphis noxia (Kurdjumov)

“…D. noxia-resistant barley varieties have also been developed and released in the U. S. (Mornhinweg et al 2002). Nevertheless, significant genetic variability occurs in D. noxia populations in Africa, Asia, Europe, North America and South America (Basky et al 2001;Almaraz et al 2003;Burd et al 2006;Dolatti et al 2005;Tolmay et al 2007). Some of these populations are virulent to varietal resistance genes.…”