Location: Cereal Crops Research
Project Number: 3060-21000-038-005-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2015
End Date: Aug 31, 2020
Objective:
The objectives of this cooperative research project are: 1) to identify and map genes and quantitative trait loci (QTL) for resistance to Fusarium head blight (FHB) and stem rust in wild emmer wheat (Triticum dicoccoides), cultivated emmer wheat (T. dicoccum), and Persian wheat (T. carthlicum); and 2) to identify and map new genes for resistance to stem rust and Hessian fly in Tausch's goatgrass (Aegilops tauschii).
Approach:
Modern wheat crop mainly consists of tetraploid durum wheat (T. durum, 2n = 4x = 28, AABB) and hexaploid bread wheat (T. aestivum, 2n = 6x = 42, AABBDD). In the primary gene pool of wheat, wild and cultivated emmer wheat (T. dicoccoides and T. dicoccum, 2n = 4x = 28, AABB genomes) are the donors of A and B genomes for durum and bread wheat, whereas Ae. tauschii is the D-genome donor for bread wheat. Persian wheat (T. carthlicum, 2n = 4x = 28, AABB) is one of the cultivated tetraploid wheat species with the same A and B genomes in durum and bread wheat. These tetraploid wheat species and Ae. tauschii are excellent sources of unique genes for resistance to many diseases and insects in wheat. Our previous studies showed that T. carthlicum accession PI 387696, T. dicoccoides PI 466979, T. dicoccum PI 193883, and Ae. tauschii RL5271 have resistance to various stem rust races. T. dicoccum PI 193883 and Ae. tauschii RL5271 also possess resistance to Fusarium head blight (FHB) and Hessian fly, respectively.
To identify and map the stem rust resistance genes (Sr) in PI 387696, PI 466979, and PI 193883 and the FHB resistance QTL in PI 193883, the three RIL (recombinant inbred line) populations with pedigrees of PI 387696/Rusty, PI 466979/Rusty, and PI 193883/Rusty that were previously developed in our program will be genotyped using the wheat 90K SNP arrays. A linkage map covering all 14 chromosomes will be then constructed with the polymorphic SNP markers for each of the populations. The three populations will be evaluated for reactions to three stem rust races (TTKSK, TRTTF, and TTTTF). The PI 193883/Rusty population will also be evaluated for FHB resistance in the greenhouse for three seasons and field nurseries in two locations for two years using a randomized complete block design with three replications. The stem rust and FHB data and the linkage maps will be used to identify the Sr genes and FHB resistance QTL. QTL analysis will be performed using the program Windows QTL Cartographer (v2.5).
To identify and map the genes for resistance to stem rust and Hessian fly in Ae. tauschii RL5271, two sub-populations each including 600 F2 plants from the cross between Ae. tauschii RL5271 and AL8/78 will be evaluated for reactions to stem rust race TPMKC and Hessian fly biotype GP (Great Plains), respectively. About 150 homozygous susceptible F2 plants will be identified from each of the sub-populations and they will be used as the mapping populations. A modified bulked segregant analysis (two parents, F1 and bulked recessive homozygotes) will be used to identify SSR (simple sequence repeat) markers linked to loci for resistance to stem rust and Hessian fly. Polymorphic markers linked to the genes will then be evaluated on the mapping populations to construct a genetic linkage map of the genes. Once the genomic regions carrying the genes are determined, the genomic sequences of Ae. tauschii AL8/78 and model species (Brachypodium and rice) will be used to develop new STS (sequence-tagged site) markers. The markers closely linked to the genes will be validated on a panel of wheat varieties and breeding lines.
