Cytogenetic study and stripe rust response of the derivatives from a wheat – Thinopyrum intermedium – Psathyrostachys huashanica trigeneric hybrid

To transfer multiple desirable alien genes into common wheat, we previously reported a new trigeneric hybrid synthesized by crossing a wheat – Thinopyrum intermedium partial amphiploid with wheat – Psathyrostachys huashanica amphiploid. Here, the meiotic behavior, chromosome constitution, and stripe rust resistance of F5 derivatives from the wheat – Th. intermedium – P. huashanica trigeneric hybrid were studied. Cytological analysis indicated the F5 progenies had chromosome numbers of 42–50 (average 44.96). The mean meiotic configuration was 1.28 univalents, 21.74 bivalents, 0.04 trivalents, and 0.02 tetravalents per pollen mother cell. In 2n = 42 lines, the average pairing configuration was 0.05 I + 19.91 II (ring) + 1.06 II (rod) + 0.003 IV, suggesting these lines were cytologically stable. Most lines with 2n = 43, 44, 46, 48, or 50, bearing a high frequency of univalents or multivalents, showed abnormal meiotic behavior. Genomic in situ hybridization karyotyping results revealed that 25 lines contained 1–7 Th. intermedium chromosomes, but no P. huashanica chromosomes were found among the 27 self-pollinated progenies. At meiosis, univalents (1–5) possessing Th. intermedium hybridization signals were detected in 19 lines. Bivalents (1–3) expressing fluorescence signals were observed in 12 lines. Importantly, 21 lines harbored wheat – Th. intermedium chromosomal translocations with various alien translocation types. Additionally, two homozygous lines, K13-668-10 and K13-682-12, possessed a pair of wheat – Th. intermedium small fragmental translocations. Compared with the recurrent parent Zhong 3, most lines showed high resistance to the stripe rust (Puccinia striiformis f. sp. tritici) pathogens prevalent in China, including race V26/Gui22. This paper reports a highly efficient technical method for inducing alien translocation between wheat and Th. intermedium by trigeneric hybridization. These lines might be potentially valuable germplasm resources for further wheat improvement.

Cytogenetic Behavior of Trigeneric Hybrid Progeny Involving Wheat, Rye and Psathyrostachys huashanica

Trigeneric hybrids are commonly used as bridges to transfer genes from some wild species to cultivated wheat and to measure the genomic interaction between donor species. We previously reported that trigeneric germplasms were produced by crossing wheat-Psathyrostachys huashanica amphiploids (PHW-SA, 2n = 8x = 56, AABBDDNsNs) with hexaploid triticale (Zhongsi 828, 2n = 6x = 42, AABBRR). In the present study, chromosome pairing behavior and the genome constitution of the F4 progenies of wheat-rye-P. huashanica trigeneric hybrids were studied. Cytological analysis showed that the chromosome number of F4 progenies ranged from 39 to 46, and 57.5% of them had 42 chromosomes. The mean meiotic configuration of F4 lines was 1.71 univalents, 20.26 bivalents, 0.04 trivalents, and 0.001 quadrivalents per pollen mother cell. Among the lines with 2n = 42, the average pairing configuration was 1.21 univalents, 16.22 ring bivalents, 4.16 rod bivalents, and 0.01 trivalents. This result indicated that these lines were cytologically stable. Other lines with 2n = 39, 40, 41, 43, 44, 45, and 46, bearing a high number of univalents or multivalents, showed abnormal meiotic behavior. Genomic in situ hybridization (GISH) revealed that all F4 lines had 11-14 rye chromosomes, but no P. huashanica chromosomes. The complete set of 14 rye chromosomes was found in 19 lines. At meiosis, GISH detected 1-6 univalents with hybridization signals of rye in 13 lines. Bivalents with fluorescence signals were identified in each line, ranging from 3 to 7. A quadrivalent with hybridization signals was observed in only 1 line, K13-714-8. Lagging chromosomes, chromosome bridges, micronuclei, and chromosome fragments hybridizing with the probe were not discovered in any of the lines. These results inferred that the behavior of rye chromosomes was normal during meiosis. In addition, 21 lines of 2n = 42 (91.3%) with 12 or 14 rye chromosomes, always contained 6 or 7 bivalents bearing fluorescence signals. This suggested that the rye chromosomes exhibiting complete pairing in these lines were cytologically stable during meiosis and may therefore be considered as new hexaploid triticales. Thus, these lines might be potential materials for further hexaploid triticale improvement.

EMS, sodium azide and gamma rays induced meiotic anomalies in Delphinium malabaricum (Huth) Munz

Meiotic cell division is a dynamic cellular process controlled by a large number of genes that act from premeiotic to postmeiotic mitosis. Mutation in these genes may cause anomalies that impair plant fertility. In this study, an attempt has therefore been made to understand the effects of ethyl methane sulfonate (EMS), sodium azide (SA) and gamma rays on the meiotic configuration of Delphinium malabaricum. The results demonstrated that the mutagens cause various types of cytological aberrations, such as univalents, chromatin bridges, laggards, fragments, stickiness and multinucleated cells. The maximum aberrations were found at higher doses/concentrations of the mutagens. The highest percentage of pollen mother cells showing abnormalities was induced by EMS followed by gamma rays and SA. The mutagen impact on chromosomal anomalies increased the frequency of pollen sterility.

Molecular cytogenetic characterization and stripe rust response of a trigeneric hybrid involving Triticum, Psathyrostachys, and Thinopyrum

Trigeneric hybrids offer opportunities to transfer alien traits into cultivated wheat. In this study, a new trigeneric hybrid involving species of Triticum , Psathyrostachys , and Thinopyrum was synthesized by crossing Triticum aestivum L. (wheat) – Thinopyrum intermedium (Host) Barkworth & D.R. Dewey amphiploid Zhong 3 with wheat – Psathyrostachys huashanica Keng ex Kuo amphiploid PHW-SA. Crossability of the two amphiploids was 19.74%, and the fertility of the hybrid was 16.20%. The mean meiotic configuration of the trigeneric hybrid (2n = 56) was 13.06 I + 17.24 IIring + 3.73 IIrod + 0.28 III + 0.04 IV. GISH analysis indicated that the trigeneric F1 had seven P. huashanica chromosomes and seven Th. intermedium chromosomes. The mean chromosome numbers of F2, F3, and F4 progenies were 2n = 49.24, 2n = 48.13, and 2n = 46.78, respectively, a gradual decrease. GISH analysis revealed that most F2 and F3 plants had 2–10 Th. intermedium chromosomes and 0–4 P. huashanica chromosomes. In the F4 progenies, 1–7 Th. intermedium chromosomes were labeled, but no P. huashanica chromosomes were detected. It seems that Th. intermedium chromosomes are more likely than P. huashanica chromosomes to be transmitted to the progenies. The stripe rust response of PHW-SA was expressed in the F1 and some F2 and F3 progenies. The trigeneric hybrid could be a useful bridge for transfering P. huashanica and Th. intermedium chromosomes to common wheat.

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The goal of the present study was to find out the best interval after hCG injection in PMSG primed prepuberal gilts for retrieval of in vivo matured oocytes for in vitro fertilisation (IVF). Altogether 66 gilts were superovulated with 1500IU PMSG and 500IU hCG 72h later. Ovum pick up was performed endoscopically 24, 28, 32 or 36h after hCG and a total of 869 cumulus-oocyte-complexes (COCs) were aspirated from 1400 follicles. COCs were tested for quality, and an aliquot was immediately fixed and stained to determine meiotic configuration. The remaining COCs were fertilised in vitro using frozen-thawed epididymal semen. Quality and developmental stage of embryos were tested after IVF, and the number of nuclei was counted. At 24 to 32h after hCG only few oocytes have entered the second meiotic cycle (18 to 25% vs. 58% at 36h, p<0.05). The overall cleavage rate was significantly influenced by insufficient maturation rate at the early collection times (14% at 24h vs. 49% at 36h). Additionally, when oocytes were collected 24 to 32h vs. 36h the cleavage rate based on mature oocytes was lower (26 vs. 62%, p<0.05). Once embryonic development has been initiated, the further in vitro development to blastocyst stages did not differ between groups. However, the number of cells was lower at collection times 24 to 32h as compared to 36h after hCG (12 to 15 cells vs. 22 cells, p<0.05). The results indicate that the time of COC collection affects the in vitro developmental competence up to the blastocyst stage and should not be performed earlier than 36h after hCG treatment.