Characterization of a partial wheat-Thinopyrum intermedium amphiploid and its reaction to fungal diseases of wheat.

Partial amphiploids between wheat (Triticum aestivum L.) and Thinopyrum species play an important role in the transfer and use of traits from alien species. A wheat-Thinopyrum intermedium partial amphiploid, TAI8335, and its alien parent were characterized by a combination of genomic in situ hybridization (GISH) and cytological observations. Evidence from GISH indicated that the donor parent Th. intermedium possessed seven pairs of S, seven J(s) and 21 J chromosomes. Mitotic observation showed that the majority of TAI8335 plants had 56 chromosomes, but a few had 54 to 55, in some cases with two to three additional telochromosomes. The chromosomes in most pollen mother cells of plants with 2n = 56 formed 28 bivalents, averaging 27.12 in 223 cells, suggesting a basic cytological stability. Sequential GISH patterns using genomic Pseudoroegneria spicata and genomic Th. intermedium DNA as probes revealed that TAI8335 had fourteen chromosomes derived from Th. intermedium and its alien genome consisted of one pair of S-, three pairs of J(s) - and one pair of J-genome chromosomes as well as two translocated chromosome pairs, one being a Robertsonian translocation and another an intercalary translocation, both of which involved J and S genome. Two of the telochromosomes in the aneuploid plants originated from the J genome and one from wheat. Disease screening demonstrated this line was highly resistant to leaf rust, stem rust, stripe rust and powdery mildew. This study showed that the partial amphiploid TAI8335 appears to serve as a novel source for the transfer of resistance genes for multiple fungal pathogens to wheat.

Molecular characterization of high molecular weight glutenin subunit allele 1Bx23 in common wheat introduced from hexaploid triticale.

High molecular weight glutenin subunit (HMW-GS) 1Bx23, an x-type subset encoded by Glu-B1p, which is only distributed in Triticum turgidum, was successfully transferred from hexaploid triticale to common wheat line SY95-71. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) shows that subunit 1Bx23 has a faster mobility than subunit 1Bx7 and 1Bx20, but slower than 1Bx17. Primers designed from the conserved regions in wheat HMW-GS gene promoter and coding sequences were used to amplify the genomic DNA of SY95-71. Total nucleotide sequences of 3426 bp including an open reading frame of 2385 bp and upstream sequence of 1038 bp were obtained. Compared with the reported gene sequences of Glu-B1-1 alleles, including 1Bx7, 1Bx14, 1Bx20 and 1Bx17, the promoter region of the 1Bx23 was displayed close to 1Bx7 and 1Bx17. The deduced amino acid sequence of coding region of 1Bx23 exhibited 34, 30, 20 and 22 amino acid substitutions from that of 1Bx14, 1Bx20, 1Bx7 and 1Bx17, respectively. A phylogenetic tree based on the nucleotide sequence alignment of the Glu-1Bx alleles shows that the 1Bx23 are apparently clustered with 1Bx7 and 1Bx17, and more ancient than 1Bx14 and 1Bx20, suggesting that the evolution speeds are different among Glu-1Bx genes. Additionally, the potential use of wheat line SY95-71 to further screen the quality contribution of unique subunit 1Bx23 is also discussed.

Molecular characterization of a wheat -Thinopyrum ponticum partial amphiploid and its derived substitution line for resistance to stripe rust.

Stripe rust (caused by Puccinia striiformis) occurs annually in most wheat-growing areas of the world. Thinopyrum ponticum has provided novel rust resistance genes to protect wheat from this fungal disease. Wheat - Th. ponticum partial amphiploid line 7430 and a substitution line X005 developed from crosses between wheat and 7430 were resistant to stripe rust isolates from China. Genomic in situ hybridization (GISH) analysis using Pseudoroegneria spicata genomic DNA as a probe demonstrated that the partial amphiploid line 7430 contained ten J(s) and six J genome chromosomes, and line X005 had a pair of J(s)-chromosomes. Giemsa-C banding further revealed that both lines 7430 and X005 were absent of wheat chromosomes 6B. The EST based PCR confirmed that the introduced J(s) chromosomes belonging to linkage group 6, indicating that line X005 was a 6J(s)/6B substitution line. Both resistance observation and sequence characterized amplified region (SCAR) markers displayed that the introduced chromosomes 6J(s) were responsible for the stripe rust resistances. Therefore, lines 7430 and X005 can be used as a donor in wheat breeding for stripe rust resistance.