S. Lhaloui

Insecticidal effects of essential oils against Hessian fly, Mayetiola destructor (Say)

Abstract Nineteen essential oils, obtained by hydrodistillation from aromatic and medicinal plants of Moroccan origin, were tested for their insecticidal effects on Hessian fly (Cecidomyiidae) adults and eggs. This insect is the major pest of wheat in Morocco. Most of the aromatic plants belong to the family Labiatae. The species Mentha pulegium, Origanum compactum, and Origanum majorana were the most toxic to adults; Ammi-visnaga, Pistacia lentiscus, O. compactum, and M. pulegium were more efficient on eggs.

Identification in Aegilops species of resistant sources to Hessian fly (Diptera: Cecidomyiidae) in Morocco

Hessian fly, Mayetiola destructor (Say), is the major insect pest of wheat in Morocco. Host plant resistance has been the most effective and practical method of controlling this pest. When 347 accessions of Aegilops species were screened in the greenhouse for resistance to Hessian fly, several accessions of Ae. geniculata Roth, Ae. triuncialis L., Ae. neglecta Req.ex Bertol., Ae. ventricosa Tausch, Ae. cylindrica Host and Ae. markgrafii (Greuter) Hammer showed resistance reaction. All expressed antibiosis as the mechanism of resistance against first instar Hessian fly larvae. These Aegilops sources of resistance could be exploited for transferring Hessian fly resistance to wheat.

Sources of resistance in primary synthetic hexaploid wheat (Triticum aestivum L.) to insect pests: Hessian fly, Russian wheat aphid and Sunn pest in the fertile crescent

Hessian fly, Mayetiola destructor (Say), Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), and Sunn pest, Eurygasterintegriceps (Puton), are among the most important insect pests of wheat in North Africa, West and Central Asia. Host plant resistance is the most economical, environmentally friendly and practical means of controlling insect pests. Through field and greenhouse screening, several sources of resistance to Hessian fly, RWA and Sunn pest have been identified in wheat and its wild relatives. To further broaden the genetic base of resistance to these pests, 914 fixed lines of synthetic hexaploid wheat (SHW) commonly designated as primary synthetic wheat were evaluated for resistance to Hessian fly, RWA and Sunn pest. The initial screenings for RWA and Sunn pest were carried out in the field at Tel Hadya, Aleppo, Syria, and for Hessian fly in the greenhouse at Tel Hadya during the 2009 and 2010 seasons. Promising accessions from the initial screening for Hessian fly, RWA and Sunn pest were evaluated for confirmation in replicated trials in the greenhouse and field. Fifteen SHWs showed high levels of resistance to Hessian fly and four showed moderate resistance. A wheat line derived from the cross (Triticum turgidum/T. dicoccoides) also showed a high level of resistance to Hessian fly. The level of resistance to RWA in SHW was considerably lower; only one SHW and one durum wheat ‘Altar 84’ exhibited a high level of resistance, while four SHW were moderately resistant. There were 21 SHW genotypes and one durum wheat ‘Langdon’ found resistant to Sunn pest feeding at the vegetative stage. Crosses between these potentially novel resistance sources and elite bread wheat were initiated. Genetic and genomic studies using these accessions are ongoing to identify and characterize the resistance genes and reveal potentially new resistance genes, which will be useful in breeding programs to develop wheat germplasm with multiple resistances to these pests.

Genetic variation among populations of the Hessian fly Mayetiola destructor (Diptera: Cecidomyiidae) in Morocco and Syria

The RAPD-PCR technique was used to study genetic variation within and among geographical populations of the Hessian fly, Mayetiola destructor (Say), from Morocco and Syria, associated with the flys ability to overcome resistance in three wheat cultivars containing H5, H13 and H22 resistance genes. Variation was detected both for the level of susceptibility of the cultivars and RAPD profiles of M. destructor populations. By the use of RAPD-PCR, high genetic variability was detected among individuals and populations of M. destructor within and between areas separated geographically. The DNA fingerprints of populations of M. destructor were area-specific with Neis measures of genetic distance ranging from 0.156 (between Abda and Beni Mellal, Morocco) to 1.977 (between Marchouch, Morocco and Lattakia, Syria). Cluster analysis of the genetic distances among the populations, identified the Syrian population as an outlier. A highly significant correlation (r = 0.81) observed between the genetic and geographic distances among the populations, provided genetic support for dispersal of the fly from its presumed origin in West Asia to Morocco.

Virulence of Hessian fly (Diptera: Cecidomyiidae) in the Fertile Crescent

The Hessian fly, Mayetiola destructor (Say), is an important insect pest of wheat (Triticum spp.) in North Africa, North America, southern Europe and northern Kazakhstan. Both wheat and this pest are believed to have originated from West Asia in the Fertile Crescent. The virulence of a Hessian fly population from Syria against a set of cultivars carrying different resistance genes, in addition to other effective sources with unknown genes, was determined in the field and laboratory at the International Center for Agricultural Research in the Dry Areas (ICARDA) during the 2005/2006 cropping season. Only two resistance genes (H25 and H26) were effective against the Syrian Hessian fly population, making it the most virulent worldwide. This high virulence supports the hypothesis that Hessian fly coevolved with wheat in the Fertile Crescent of West Asia. The ICARDA screening programme is using this Hessian fly population to identify new resistance genes to this pest.

Wheat genetic control of Hessian fly (Diptera: Cecidomyiidae) in Morocco

Abstract Hessian fly, Mayetiola destructor (Say), causes about 30% yield reduction on both durum wheat and bread wheat in Morocco. Major effort has been put on host plant resistance for control of this pest. Field and greenhouse experiments demonstrated that resistance genes H5, H11, H13, H14H15, H21, H22, H23, H25, and H26 are very effective. They all express antibiosis as a mechanism of resistance, whereby first instars die after they start feeding on plants carrying resistance genes. By contrast, H7H8 and H9 are only moderately resistant against Hessian fly in Morocco. Five other sources of resistance in bread wheat were identified: Massira, BT92P1.20: NS732/Herm, L222, L254 and ADC14. All of these resistance genes have been incorporated into Moroccan wheats. Two bread wheat cultivars, Saada (H5) and Massira (tolerant), were released to farmers in 1989 and 1994, respectively. Two bread wheat lines carrying H13 and H22 genes and L222 are in registration yield trials. No source of resistance for Hessian fly in durum wheat was identified. H5 and H11 genes, located on the A genome, have been transferred from bread wheat to durum wheat. H21 and H25 genes, located on B genome, are being transferred from bread wheat to durum wheat.

Biotypes of Hessian fly (Dipt., Cecidomyiidae) in Morocco

Hessian fly, Mayetiola destructor (Say), is the most important insect pest of wheat in Morocco, where host plant resistance has been used successfully for control. Our objective was to determine the frequency of Hessian fly virulence on H5, H13 and H22 resistance genes. Five Hessian fly populations from the principal cereal‐growing regions in Morocco were studied. The variability in percentage of susceptible plants across Hessian fly populations was highly significant (P < 0.01), indicating differences in virulence frequencies. Plants with the H13 gene had the lowest percentage of susceptible plants, 1.77 and 1.51%, when infested with Hessian flies from Fes and Marchouch, respectively. A low level of virulence to H22 was detected in Fes, Abda and Marchouch populations, 1.87, 1.54 and 1.99% susceptible plants, respectively. The level of virulence to H5 was low in all the five populations. The Beni Mellal population gave the highest percentage of susceptible plants carrying H13 and H22 genes, 6.43 and 7.28%, respectively. The size of live larvae on susceptible plants of the three cultivars carrying H5, H13 and H22 was similar to that of the susceptible check, indicating that a true virulence (biotype) is developing in Hessian fly populations in Morocco. Thus, continuous monitoring of the development of Hessian fly biotypes is essential for optimal deployment of resistance genes.

First source of resistance in durum wheat to Hessian fly (Diptera: Cecidomyiidae) in Morocco

Hessian fly, Mayetiola destructor (Say), is the major pest of wheat in North Africa. In Morocco, durum wheat (Triticum turgidum L. subsp. durum (Desf). Husn.) losses due to this pest have been estimated at 32%. Genetic resistance is the only economical and practical means of controlling this insect. Field and greenhouse screening of durum wheat genotypes resulted in the identification of one source of resistance to Hessian fly in Morocco. This is the first source of durum wheat Hessian fly-resistance identified in Morocco. This source of resistance expresses a medium level of antibiosis against first-instar Hessian fly larvae; about 25% of the larvae survive on resistant plants. The deployment of varieties that allow for larval survival on resistant plants should reduce selection for biotype development. This source of resistance is being used by CIMMYT/ICARDA and Moroccan breeders to develop resistant durum wheat varieties.