Molecular cytogenetic discrimination and reaction to wheat streak mosaic virus and the wheat curl mite in Zhong series of wheat – Thinopyrum intermedium partial amphiploids

Abstract

Thinopyrum intermedium (2n = 6x = 42, JJJsJsSS) is potentially a useful source of resistance to wheat streak mosaic virus (WSMV) and its vector, the wheat curl mite (WCM). Five partial amphiploids, namely Zhong 1, Zhong 2, Zhong 3, Zhong 4, and Zhong 5, derived from Triticum aestivum x Thinopyrum intermedium crosses produced in China, were screened for WSMV and WCM resistance. Zhong 1 and Zhong 2 had high levels of resistance to WSMV and WCM. The other three partial amphiploids, Zhong 3, 4, and 5, were resistant to WSMV, but were susceptible to WCM. Genomic in situ hybridization (GISH) using a genomic DNA probe from Pseudoroegneria strigosa (SS, 2n = 14) demonstrated that two partial amphiploids, Zhong 1 and Zhong 2, have almost the identical 10 Th. intermedium chromosomes, including four Js, four J, and two S genome chromosomes. Both of them carry two pairs of J and a pair of Js genome chromosomes and two different translocations that were not observed in the other three Zhong lines. The partial amphiploids Zhong 3, 4, and 5 have another type of basic genomic composition, which is similar to a reconstituted alien genome consisting of four S and four Js genome chromosomes of Th. intermedium (Zhong 5 has two Js chromosomes plus two Js-W translocations) with six translocated chromosomes between S and Js or J genomes. All three lines carry a specific S-S-Js translocated chromosome, which might confer resistance to barley yellow dwarf virus (BYDV-PAV). The present study identified a specific Js2 chromosome present in all five of the Zhong lines, confirming that a Js chromosome carries WSMV resistance. Resistance to WCM may be linked with J or Js chromosomes. The discovery of high levels of resistance to both WSMV and WCM in Zhong 1 and Zhong 2 offers a useful source of resistance to both the virus and its vector for wheat breeding programs.

A new long terminal repeat (LTR) sequence allows to identify J genome from JS and St genomes of Thinopyrum intermedium

“…is a hexaploid species (2n=6x=42) with genomes E 1 E 2 St (Wang et al 1994) or JJ S St (Chen et al 1998). The species has been hybridized extensively with wheat and proved to be a valuable source of genes for disease resistance (Larkin et al 1995;Chen et al 2003;Yang et al 2006;Luo et al 2009) and tolerance to salt stress (Dvořák 1985). The correct identification of Th.…”

Molecular characterization of a cryptic wheat-Thinopyrum intermedium translocation line: evidence for genomic instability in nascent allopolyploid and aneuploid lines

“…intermedium genome (He et al, 1988), whereas others assume that they are from different Th. intermedium genomes, and have constituted a "synthetic" genome (Fedak et al, 2000;Chen et al, 2003). In the present work, of the mapped sequence/enzyme combinations (S/Es) analyzed, none of the six polymorphic S/Es, which mapped to the homoeologous group 1, detected the presence of Th.…”

“…intermedium and those of wheat, the 14 chromosomes in Zhong3 originated from Th. intermedium probably do not include the homoeologous group 1, therefore favoring the view that the 14 chromosomes do not belong to a single and complete genome (Fedak et al, 2000;Chen et al, 2003). We noted, however, that due to the extensive genomic restructuring or changes at the DNA level in the octoploid, as will be detailed below, it also is possible that the six homoeologous group 1 S/Es used may happen to be in those loci, being lost in Zhong3 (Table 1).…”

Cytogenetic and molecular identification of a new wheat-Thinopyrum intermediumaddition line with resistance to powdery mildew

“…intermedium in the wheat background were clearly distinguished (Chen et al 2003(Chen et al , 2005Bao et al 2009). About the genomic composition of Th.…”