The genus Brassica contains several important crop species that are used for a variety of purposes. Brassica napus and Brassica rapa are the most important ones for their use as oilseed crops. In Brassica , interspecific hybridization is a potential and useful method for transferring valuable traits between species of commercial interest. For breeding Brassicas resistant to some diseases, i.e. clubroot, attempts of transferring resistant genes (CR) through interspecific hybridization have also been reported. The main step in the introgression process is the production of interspecific hybrids between the two species. However, the cross-incompatibility occurring in wide hybridization might hamper the possibility of obtaining hybrid progenies. For that reason, the crossability study is essential and may give an insight into the cross-compatibility relationship among the species, the direction of success of crossing, and the crossability barriers of some combinations, if any. In the present study, interspecific reciprocal crosses between B. napus and B. rapa ssp. chinensis genotypes were carried out in order to determine their crossability and to produce their F1 hybrids. Crossability was analyzed based on the pollen germination index (PGI) and the development of hybrid embryos in in vitro cultures. It was observed that the unilateral interspecific incompatibility occurred in crosses between B. napus × B. rapa ssp. chinensis. When B. napus cultivars were used as a maternal parent, pollen grains of B. rapa germinated well on the stigmas, while only a small number of pollen tubes could elongate near the ovules, resulting in a low development of hybrid embryos. Using the B. rapa ssp. chinensis as the pistillate parent in the crosses, it was found that the crossability was relatively higher than that in the case of the reciprocal cross. This resulted in a greater number of embryos obtained. Generally, it was concluded that the selection of parental components for hybridization is an important step for obtaining breeding success.
In Brassica, interspecific hybridization is a potential and useful method for transferring valuable traits between species of commercial interest. In the previous experiments successful interspecific hybrids were obtained through hybridization between chosen rapeseed cultivars (Brassica napus L.) and Brassica rapa genotypes for transferring clubroot resistance from wild species into cultivated background. In the presented research morphological, cytological and simple sequence repeats (SSR)based molecular analyses were carried out to confirm the hybrid nature of the F1 plants. This paper evidences for a successful creation of twenty three F1 interspecific hybrids where six out of eleven cross combinations were confirmed as fertile. The obtained results have shown that analyzed morphological characters of F1 hybrids were intermediate as compared to those of both parental genotypes. Furthermore, in pollen mother cells (PMCs) of the F1 hybrids abnormalities like univalent, lagging chromosomes and disorders in synchronization were observed in meiosis. Generally, the abnormalities in meiosis occurred in most of the tested genotypes with the mean frequency of 63.8%. Among tested SSR primers, Na10-A08 was found to reveal highly polymorphic bands in hybrids. As a result, 41.1% of the investigated plants were confirmed as true hybrids.
OBJECTIVE To describe and classify cervical muscle jerks associated with cervical pain or myelopathy and evaluate their clinical and diagnostic relevance. ANIMALS 20 dogs with a history of unilateral or bilateral cervical jerks associated with cervical pain or myelopathy. PROCEDURES A retrospective study. Detailed history, complete clinical and neurological examinations, CT studies, and outcome were available for each dog. All dogs received a treatment adapted to each diagnosis. The presence or absence of jerks was evaluated at short- and long-term recheck examinations. An immediate postoperative CT scan was obtained for all cases that were treated surgically. RESULTS 20 dogs were selected for the study, 13 of which were French Bulldogs. Jerks all presented as focal repetitive rhythmic contractions on the lateral aspect of the neck (on one or both sides). All dogs had a diagnosis of cervical intervertebral disk extrusion (IVDE), half of them at the C2-C3 level. No dogs presented with extrusion caudal to the C4-C5 intervertebral disk space. The prevalence of myoclonia among all dogs diagnosed with IVDE was 3.77% (20/530) in our hospital. CLINICAL RELEVANCE Cervical jerk associated with cervical pain or myelopathy may represent myoclonus and was exclusively secondary to cranial cervical IVDE in this study. Full recovery was observed following medical or surgical treatment of IVDE. The exact origin and classification of this involuntary movement has yet to be established.
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