Cytogenetic mapping of a major locus for resistance to Fusarium head blight and crown rot of wheat on Thinopyrum elongatum 7EL and its pyramiding with valuable genes from a Th. ponticum homoeologous arm onto bread wheat 7DL

Abstract

A major locus for resistance to different Fusarium diseases was mapped to the most distal end of Th. elongatum 7EL and pyramided with Th. ponticum beneficial genes onto wheat 7DL. Perennial Triticeae species of the Thinopyrum genus are among the richest sources of valuable genes/QTL for wheat improvement. One notable and yet unexploited attribute is the exceptionally effective resistance to a major wheat disease worldwide, Fusarium head blight, associated with the long arm of Thinopyrum elongatum chromosome 7E (7EL). We targeted the transfer of the temporarily designated Fhb-7EL locus into bread wheat, pyramiding it with a Th. ponticum 7elL segment stably inserted into the 7DL arm of wheat line T4. Desirable genes/QTL mapped along the T4 7elL segment determine resistance to wheat rusts (Lr19, Sr25) and enhancement of yield-related traits. Mapping of the Fhb-7EL QTL, prerequisite for successful pyramiding, was established here on the basis of a bioassay with Fusarium graminearum of different 7EL-7elL bread wheat recombinant lines. These were obtained without resorting to any genetic pairing promotion, but relying on the close 7EL-7elL homoeology, resulting in 20% pairing frequency between the two arms. Fhb-7EL resided in the telomeric portion and resistant recombinants could be isolated with useful combinations of more proximally located 7elL genes/QTL. The transferred Fhb-7EL locus was shown to reduce disease severity and fungal biomass in grains of infected recombinants by over 95%. The same Fhb-7EL was, for the first time, proved to be effective also against F. culmorum and F. pseudograminearum, predominant agents of crown rot. Prebreeding lines possessing a suitable 7EL-7elL gene/QTL assembly showed very promising yield performance in preliminary field tests.

Harnessing Genetic Diversity of Wild Gene Pools to Enhance Wheat Crop Production and Sustainability: Challenges and Opportunities

“…elongatum 7EL arm (Fhb-7EL). In this case, due to the close homoeology relating the 7el1L and 7EL arms, as confirmed by cytological (meiotic chromosome pairing) and molecular (genetic map synteny and collinearity) evidence [43], even in the absence of any genetic pairing promotion (e.g., ph1 mutation), target genes from the two Thinopyrum species could be brought together in a single alien segment on wheat 7DL with relative ease. The array of segregating progeny from the cross between the two donor lines has been recently widened.…”

“…The array of segregating progeny from the cross between the two donor lines has been recently widened. The 114 total plants tested with appropriate molecular markers (Figure 3), have revealed a total frequency of recombinant types of over 14%, which is higher than the 10.6% that was previously estimated on a smaller sample [43]. Of these, equal number of T4 and 7E types were isolated in the cross progeny of (CS7E(7D) × T4) F1s with normal bread wheat cultivars, used as pollen parents (Figure 3).…”

“…A remarkable successful attempt [43] involved the bread wheat T4 translocation line, containing Lr19 and associated genes/QTL on the Th. ponticum 7el 1 L portion, and the bread wheat cv.…”

“…Of these, equal number of T4 and 7E types were isolated in the cross progeny of (CS7E(7D) × T4) F 1 s with normal bread wheat cultivars, used as pollen parents (Figure 3). A remarkable successful attempt [43] involved the bread wheat T4 translocation line, containing Lr19 and associated genes/QTL on the Th. ponticum 7el1L portion, and the bread wheat cv.…”

“…Identification and characterization of the various recombinant types was enabled by use of GISH (genomic in situ hybridization) and by several molecular markers (see Figure 3 and [43]), which highlighted the different 7EL-7el1L breakpoints. The most polymorphic and user-friendly of such Figure 3.…”