Identification of a Wheat-Psathyrostachys huashanica 7Ns Ditelosomic Addition Line Conferring Early Maturation by Cytological Analysis and Newly Developed Molecular and FISH Markers

Abstract

Early maturation is an important objective in wheat breeding programs that could facilitate multiple-cropping systems, decrease disaster- and disease-related losses, ensure stable wheat production, and increase economic benefits. Exploitation of novel germplasm from wild relatives of wheat is an effective means of breeding for early maturity. Psathyrostachys huashanica Keng f. ex P. C. KUO (2n=2x=14, NsNs) is a promising source of useful genes for wheat genetic improvement. In this study, we characterized a novel wheat-P. huashanica line, DT23, derived from distant hybridization between common wheat and P. huashanica. Fluorescence in situ hybridization (FISH) and sequential genomic in situ hybridization (GISH) analyses indicated that DT23 is a stable wheat-P. huashanica ditelosomic addition line. FISH painting and PCR-based landmark unique gene markers analyses further revealed that DT23 is a wheat-P. huashanica 7Ns ditelosomic addition line. Observation of spike differentiation and the growth period revealed that DT23 exhibited earlier maturation than the wheat parents. This is the first report of new earliness per se (Eps) gene(s) probably associated with a group 7 chromosome of P. huashanica. Based on specific locus-amplified fragment sequencing technology, 45 new specific molecular markers and 19 specific FISH probes were developed for the P. huashanica 7Ns chromosome. Marker validation analyses revealed that two specific markers distinguished the Ns genome chromosomes of P. huashanica and the chromosomes of other wheat-related species. These newly developed FISH probes specifically detected Ns genome chromosomes of P. huashanica in the wheat background. The DT23 line will be useful for breeding early maturing wheat. The specific markers and FISH probes developed in this study can be used to detect and trace P. huashanica chromosomes and chromosomal segments carrying elite genes in diverse materials.

Cytogenetic and Molecular Marker Analyses of a Novel Wheat–Psathyrostachys huashanica 7Ns Disomic Addition Line with Powdery Mildew Resistance

“…Previous studies have illustrated that all seven Ns chromosomes from P. huashanica that have been introduced into common wheat exhibit excellent characteristics with regard to disease resistance and agronomic traits. Examples include 2Ns, 3Ns, 4Ns, and 5Ns disomic addition lines and a 1Ns (1D) disomic substitution line with resistance to stripe rust [ 35 , 36 , 37 , 38 ], 1Ns and 7Ns disomic addition lines with resistance to leaf rust [ 24 , 39 ], 6Ns and 7Ns addition lines maturing earlier than their wheat parents [ 25 , 40 ], and a 2Ns (2D) disomic substitution line with a high level of resistance to wheat take-all [ 41 ]. In addition, a 4Ns disomic addition line has been found to have enhanced tiller numbers [ 38 ], and a 1Ns disomic addition line was reported to exhibit increased storage of microelements in seeds [ 42 ].…”

“…For instance, 25 specific PCR markers for D. villosum chromosome 6V#4S carrying the PmV gene have been developed by RNA-seq [ 59 ]. As another example, we previously used SLAF-seq technology to develop 45 markers specific for one arm of P. huashanica chromosome 7Ns to efficiently identify 7Ns chromosome segments carrying earliness per se genes in a wheat background [ 25 ]. Compared with the above-mentioned technologies, GBS is a simpler, more robust, and more cost-effective approach [ 60 ]; it is also more suitable for the development of large-scale molecular markers in Triticeae species without reference genome sequences, such as for tetraploid Thinopyrum elongatum chromosomes 1E and 4E [ 53 , 61 ].…”

“…For the mc-FISH analysis, the synthetic oligonucleotide probes Oligo-pSc119.2 and Oligo-pTa535 were used to identify individual wheat chromosome [ 31 ]. The repetitive DNA probe pPh37, which was labeled by the nick translation method using an Atto488 NT labeling kit, allowed all P. huashanica chromosomes to be unambiguously distinguished from wheat chromosomes [ 25 ]. The mc-FISH procedure was conducted as described by Li et al [ 61 ] and Han et al [ 67 ] with slight modifications.…”

“…With the aim of making these favorable genes of P. huashanica accessible for wheat breeding, intergeneric hybrids between common wheat and P. huashanica were successfully synthesized through distant hybridization and embryo rescue in the 1980s [ 19 ]. Subsequently, an array of wheat– P. huashanica derivative lines were successively generated, including intergeneric amphiploids [ 22 ], addition [ 23 , 24 , 25 ], substitution [ 26 , 27 ], and translocation [ 20 , 28 , 29 ] lines. Compared with their recipient wheat parents, these progeny lines with single P. huashanica chromosomes or chromosomal segments incorporated into the common wheat background have performed extremely well and have thus proven to be valuable germplasm resources for wheat genetic improvement.…”

“…In previous research in our laboratory, we successfully introduced desirable genes from P. huashanica into common wheat by intergeneric hybridization to produce a series of wheat– P. huashanica derived lines, including addition, translocation, and some unrecognized hybrid lines [ 20 , 25 , 30 ]. In the present study, we selected 18-1-5, a novel wheat– P. huashanica disomic addition line highly resistant to powdery mildew, from the BC 1 F 5 progeny of a cross between P. huashanica and common wheat lines Chinese Spring (CS) and a CS ph2b mutant (CS ph2b ).…”