3. The Hybrid Embryo and Xenogenic Desire

The cross-incompatibility barrier between 4x wheat and rye has limited the genetic base for triticale breeding. Experiments designed to improve the synthesis of wheat-rye amphihaploids were conducted. The effects of 2,4-D on crossability and 3x hybrid embryo differentiation, and the influence of one-step and two-step media on the culture of immature 3x embryos in vitro, were investigated. Application of 10 mg L-1 2,4-D slightly improved seed set but significantly reduced the frequency of normal embryos. In contrast to the reported favourable effect of 2,4-D on haploid embryo formation in wheat × maize crosses, the application of 2,4-D in the present study offers no real advantage on amphihaploid embryo formation from 4x wheat × rye crosses. For small and immature wheat-rye hybrid (3x) embryos, optimum recovery in vitro was obtained via a two-step procedure consisting of a semi-solid MN medium followed by MS medium supplemented with IAA (1 mg L-1) and BAP (1 mg L-1). For bigger and well-differentiated embryos, the use of a one-step Gamborg's B5 medium was sufficient.

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Isozymes and morphology of five amphibian hybrid embryo combinations which develop beyond gastrulation

Canadian Journal of Zoology ◽

10.1139/z75-114 ◽

1975 ◽

Vol 53 (8) ◽

pp. 992-1002 ◽

Cited By ~ 6

Author(s):

Richard P. Elinson

Keyword(s):

Lactate Dehydrogenase ◽

Neural Tube ◽

Tissue Differentiation ◽

External Morphology ◽

Morphological Development ◽

Enzyme Expression ◽

Control Stage ◽

Hybrid Embryo

Hybrid embryos were produced by inseminating R. clamitans or R. septentrionalis eggs with R. catesbeiana, R. pipiens, or R. septentrionalis sperm. They were examined for morphological development and for paternal enzyme expression. One of the hybrid combinations was viable while the others arrested after neurulation but before feeding. Gastrulation and neurulation did not guarantee further tissue differentiation nor even a well-formed neural tube. The internal and external morphology of an arrested hybrid was characteristic for that particular egg–sperm combination. Regardless of the degree of morphological development, expression of a paternal gene for lactate dehydrogenase (LDH) was detected in three of the hybrid combinations when control embryos were at stages 19 or 20. Paternal forms of three other enzymes were detected in some of the hybrids after control stage 20.In addition, a polymorphism in LDH was found in R. clamitans. As determined genetically, there are at least three alleles of the B gene of LDH in the R. clamitans population.

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Progesterone promotes fetal growth in a restricted interspecies gestation (Ovis canadensis x Ovis aries)

Veterinaria México OA ◽

10.22201/fmvz.24486760e.2018.3.507 ◽

2018 ◽

Vol 5 (3) ◽

Author(s):

Octavio Mejía Villanueva ◽

Verónica Hernández Cazadero ◽

Clara Murcia Mejía ◽

Susana Rojas Maya ◽

Cristina Castaño García ◽

...

Keyword(s):

Ex Situ Conservation ◽

Treated Group ◽

Ovis Canadensis ◽

Ovis Aries ◽

Ex Situ ◽

Domestic Sheep ◽

Foetal Growth ◽

Daily Dose ◽

Hybrid Embryo ◽

Lower Fertility

Progesterone promotes foetal growth in a restricted interspecies gestation (Ovis canadensis × Ovis aries). Veterinaria México OA. 2018;5(3).Gestations between bighorn (Ovis canadensis) and domestic sheep (O. aries) can be considered for ex situ conservation of bighorn. In the first experiment, domestic sheep were inseminated with bighorn or domestic semen. Bighorn inseminated sheep showed lower fertility than domestic inseminated sheep (40% vs. 65%, p = 0.11). Bighorn inseminated sheep had longer gestation periods (152.13 days vs. 146.54 days, p < 0.001) and lower progesterone levels during the last third. Hybrid lambs weighed less than domestic lambs (2.46 kg vs. 5.10 kg, p < 0.001). Their placentas were not as long (48.67 cm vs. 72.17 cm, p < 0.001), were less wide (17.83 cm vs. 23.83 cm, p < 0.001), and the weight of cotyledons was lower (1.50 g vs. 3.20 g, p < 0.001). In the second experiment, hybrid embryos (O. canadensis × O. aries) were transferred into domestic recipients, and pregnant ewes were divided into the treated group, which had a progesterone daily dose of 25 mg from weeks 7 to 20, and the non treated group. Gestation in domestic sheep that received one hybrid embryo and progesterone reached 152.60 days, which was similar to the 153.33 days (p = 0.51) in the non treated sheep. Hybrid offspring of the group treated with progesterone were heavier, 3.41 kg, than the control, 2.21 kg (p < 0.001), and their placentas were longer (71.20 vs. 50.83 cm, p = 0.002). Although progesterone levels were lower in domestic females inseminated with bighorn and in the recipients of hybrid embryos, it is possible to establish pregnancies between both species and the birth of viable offspring. The administration of progesterone during gestation increases the length of the placenta and promotes higher birth weights of hybrids.Figure 1. Progesterone (ng/mL) in interspecies gestations (O. c. mexicana × O. aries, n = 6) and intraspecies gestations (O. aries × O. aries, n = 6).*Statistically different values (p < 0.01).

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