Two Step Transfer of Rye-Derived Hessian Fly- Resistance Gene H21 to Durum Wheat by Compensating Robertsonian Translocation and Induced Homoeologous Recombination.

Abstract

The Hessian fly resistance gene H21 is present on the wheat-rye wholearm translocation T2BS·2RL and was recently transferred to durum wheat. However, homozygous lines for this translocation have poor plant vigor, low seed set, and are almost completely sterile, making it impossible to use this germplasm directly in durum wheat improvement. The objective of this study was to reduce the rye segment in T2BS·2RL using ph-mediated recombination, thereby making this gene available for durum breeding. A total of 39 primary recombinants from a population of 512 plants (7.6%) were recovered involving 10% of the distal segment of the long arm of rye or wheat. Among these primary recombinants 21 (53.8%) had distal rye chromatin, 12 (30.8%) had distal wheat chromatin, the remaining four had either very distal wheat or rye and two were interstitial recombinants. Ten out of 39 primary recombinants were tested for their resistance to Hessian fly. Three recombinants (Rec. # 1, 2, 3) with about the distal 10% of 2BL arm derived from rye reacted resistant and, thus, had the H21 gene. Two recombinants (Rec. # 4, 5) with very distal rye chromatin reacted susceptible to the Hessian fly. Three other primary recombinants (Rec. # 6,7,8) with the distal 10% of the 2RL arm derived from wheat were susceptible to Hessian fly and did not retain the H21 gene. The remaining two recombinants (Rec. # 9, 10) with very distal wheat segments were resistant and still had the resistance gene H21. The distal primary recombinants with the gene were vigorous and had normal seed set and can now be used in the improvement of durum wheat. Introduction:-The Hessian fly, Mayetiola destructor (Say), is a major insect pest of wheat. Genetic resistance is the most effective and economical means of controlling this insect (Ratcliffe and Hatchett 1997). To date, 29 Hessian fly-resistance genes (H1 through H29) have been identified in Triticum/Aegilops species and in Secale cereale L. (McIntosh et al., 1998). The mechanism of resistance conditioned by these genes is antibiosis, whereby first instars die soon after they begin to feed on plants. A gene-for-gene relationship exists between the resistance in wheat and avirulence in the Hessian fly. Virulence in the insect is conditioned by homozygous recessive pairs of genes (Hatchett and Gallun 1970). As a consequence of this highly specific interaction, 16 biotypes (designated Great Plains and A through O) have been isolated from field populations and are distinguished only by their ability or inability to survive on and stunt wheat with specific resistance genes.Triticum Turgidum L. is an important crop in the Mediterranean region and is grown on approximately 17 millions hectares. Lacking adequate levels of resistance, this crop usually is damaged severely by Hessian fly in the dry areas of northern Africa. In Morocco, yield losses due to damage by this insect have been estimated at up to 36% of the yearly small grain production . Among the identified genes for resistance to Hessian fly, ten have been found to b...

Molecular Cytogenetic Analysis of Radiation-Induced New Translocation From a Wheat Line With a Rye Ditelosome 2rl Carrying the Hessian Fly Resistance Gene H21.

“…The second step of such transfers can be accomplished either by homologous recombination to stack more genes in the alien chromosome arm as was first done (Friebe et al 1994;Jiang et al, 1994b) in transferring the powdery mildew gene Pm20 from 6RL to the existing translocation T6BS•6RL. In the case of non-homologous arms, the reduction of the alien segment can be accomplished by induced homoeologous recombination as was shown by Ferrahi et al (2017a).…”

“…Very little progress has been made in durum wheat(Dvorak and Lukaszewski 2000;Dvorak and Gorham 1992;Dvorak et al 1994;Luo et al 1996b;Ceoloni et al 1996, Ferrahi et al, 2017a, Ferrahi et al, 2017b, probably because the a b buffering ability of tetraploid durum wheat is less than that of hexaploid wheat. Other sources of resistance need to be used in durum wheat improvement to increase the genetic variability.…”