Evaluation of Brassica oleracea accessions for resistance to Plasmodiophora brassicae and identification of genomic regions associated with resistance.

Clubroot disease caused by Plasmodiophora brassicae is a challenge to Brassica crop production. Breakdown of resistance controlled by major genes of the Brassica A genome has been reported. Therefore, identification of resistance in the Brassica C genome is needed to broaden the genetic base of resistance in Brassica napus canola. In this study, we evaluated 135 Brassica oleracea accessions, belonging to eight variants of this species to identify resistant accessions as well as to identify the genomic regions associated with resistance to two recently evolved P. brassicae pathotypes, F3-14 (3A) and F-359-13 (5X L-G2). Resistance to these pathotypes was observed more frequently in var. acephala (kale) followed by var. capitata (cabbage); few accessions also carried resistance to both pathotypes. Association mapping using single nucleotide polymorphism (SNP) markers developed through genotyping by sequencing technique identified 10 quantitative trait loci (QTL) from six C-genome chromosomes to be associated with resistance to these pathotypes; among these, two QTL associated with resistance to 3A and one QTL associated with resistance to 5X L-G2 carried ≥3 SNP markers. The 10 QTL identified in this study individually accounted for 8%-18% of the total phenotypic variance. Thus, the results from this study can be used in molecular breeding of Brassica crops for resistance to this disease.

The effects of amniotic fluid on the histopathologic changes of exposed spinal cord in fetal sheep.

BACKGROUND: Experimental studies have shown that in myelomeningocele, the primary malformation is neural tissue damage resulting from exposure of neural tissue to amniotic fluid. In this study, the effects of amniotic fluid on histopathologic changes of exposed spinal cord in fetal sheep were evaluated. METHODS: In an experimental trial, 10 fetal sheep in two groups containing five subjects (group A) and five shams (group B) were studied. In the sheep at 90 - 100 days of gestation (term: 145 - 150 days) the lumbar skin was incised, paraspinal soft tissues were excised, laminectomy was performed at L2 - L4, and dura matter was opened. In group A, the dura matter was not dorsally closed and thus the spinal cord was left exposed to amniotic fluid, and in group B the skin was immediately closed. The lambs were delivered near term by cesarean section and were assessed clinically and morphologically. RESULTS: In group A, all lambs (n=5) had a complete or incomplete flaccid sensorimotor paraplegia and suffered from urine incontinence. Four lambs in this group were stool incontinent. In group B (n=4), only one lamb had paraparesis (P=0.048) and all lambs were urine and stool continent. In group A, all lambs had hypoplastic longitudinal muscles of the rectum but well- developed circular muscles. The anal sphincter muscles did not develop normally. In group B, all lambs had well-developed longitudinal and circular muscles and anal sphincter muscles developed normally (P=0.048). Histopathologic examination of the spinal cords showed edema, focal calcification, fibrosis, and capillary cell proliferation in group A, but in group B such changes were not seen. The number of ganglion cells was significantly higher in group B compared with group A (P<0.0005). CONCLUSION: Exposure of spinal cord to amniotic fluid causes structural neural tissue damage that can be prevented by fetal surgery through repairs of myelomeningocele.

Evaluation of diluted amniotic fluid effects on histological changes of intestine of rabbit fetus with gastroschisis.

Amniotic fluid exchange is a method for prevention of intestinal damage in gastroschisis, but its techniques are different in studies. We investigated the effects of amnioinfusion exchange on histological changes of intestine and feasibility and safety of amniotic fluid exchange through central vein catheter (CVC) placed in pregnant rabbit uterus. A total of 15 pregnant New Zealand white rabbits were selected. Fetuses were randomly divided into three groups (case, control, sham). On gestational day 25, under general anesthesia with midline laparotomy, the graved bicornuate uterus was exposed. In controls, fetus abdomen was opened by a transverse incision in right lower quadrant region and intestines were eviscerated. In cases, after intestine evisceration, a central venous catheter was passed from mother skin and uterus and fixed to uterus wall. In shams, fetus was delivered on gestational day 32 and its abdomen was opened. In case group, after operation, 1-2 cc of warm saline solution was replaced through catheter every 6 h. On gestational day 32, fetuses of case and control groups were delivered. Mucosal and serosal thickness, muscle thickness, fibrin deposition, serosal collagen and ganglia were compared. Ten fetuses as shams, 7 fetuses as controls and 7 fetuses as case group were studied. Serosal thickness was 4.5 +/- 3.6 microm in shams, 64.2 +/- 28.7 microm in controls and 6 +/- 4.1 microm in cases. Serosal thickness in control group was higher than sham (P < 0.001) and case (P < 0.002) groups. In case group, infiltration of inflammatory cells with mild edema without fibroblast infiltration was seen. Application of the CVC technique was found to be a simple procedure that effectively decreased serosal inflammatory response of intestine in gastroschisis.