Assessment of DNA markers for seed contamination testing and selection of disease resistance in cabbage

Cabbage (Brassica oleracea L. var. capitata) is an important vegetable worldwide. Most Japanese commercial cultivars of cabbage use an F₁ hybrid seed production system. The purity of F₁ hybrid seeds is important and the assessment of purity based on DNA markers can be highly accurate. In addition, selection of agronomically important traits such as disease resistance based on DNA markers is useful for breeding of cabbage. The aim of this study is to demonstrate the effectiveness of DNA marker-assisted selection in cabbage. In this study we distinguished the parental S haplotypes in 35 F₁ hybrid cultivars by combining several linked DNA markers. Thirty-one highly polymorphic simple sequence repeats (SSR) markers were screened from 175 reported SSR markers, which are useful for assessment of the purity of F₁ hybrid seeds. We examined the relationship between the DNA marker based genotype and the phenotype by an inoculation test of clubroot disease. A co-dominant PCR–RFLP marker was developed for selection of Fusarium yellows resistance and the genotypes using this marker were consistent with inoculation test in all tested samples.     

Production of high yield short duration Brassica napus by interspecific hybridization between B. oleracea and B. rapa

Brassica napus is a leading oilseed crop throughout many parts of the world. It is well adapted to long day photoperiods, however, it does not adapt well to short day subtropical regions. Short duration B. napus plants were resynthesized through ovary culture from interspecific crosses in which B. rapa cultivars were reciprocally crossed with B. oleracea. From five different combinations, 17 hybrid plants were obtained in both directions. By self-pollinating the F₁ hybrids or introgressing them with cultivated B. napus, resynthesized (RS) F₃ and semi-resynthesized (SRS) F₂ generations were produced, respectively. In field trial in Bangladesh, the RS B. napus plants demonstrated variation in days to first flowering ranging from 29 to 73 days; some of which were similar to cultivated short duration B. napus, but not cultivated short duration B. rapa. The RS and SRS B. napus lines produced 2–4.6 and 1.6–3.7 times higher yields, respectively, as compared to cultivated short duration B. napus. Our developed RS lines may be useful for rapeseed breeding not only for subtropical regions, but also for areas such as Canada and Europe where spring rapeseed production can suffer from late spring frosts. Yield and earliness in RS lines are discussed.     

Possible causes of diabetes mellitus in cattle infected with bovine viral diarrhoea virus.

In cattle, we encountered insulin-dependent diabetes mellitus (IDDM) associated with bovine viral diarrhoea virus (BVDV) infection. To estimate the correlation between IDDM and BVDV infection, the distribution of BVDV in the pancreas and islet-cell antibody (ICA) were investigated. The distribution of BVDV in the pancreas was examined by in situ hybridization using two oligonucleotide probes that recognized the gp25- and p14-coding regions of the BVDV gene. ICA was examined by indirect fluorescence antibody assay using the sera from affected cattle and pancreata from normal cattle. In the pancreata of all BVDV-infected cattle, including IDDM-complicated cattle, oligonucleotide probe hybridized portions were recognized. In short, BVDV genes were detected not only in IDDM-complicated cattle but also in uncomplicated cattle. Moreover, there was no hybridized portion in the islet cells. In BVDV-infected and IDDM-complicated cattle, ICA was frequently detected. On the other hand, ICA was not detected in BVDV-infected and IDDM uncomplicated cattle. These results suggest that IDDM associated with BVDV infection is not a direct effect of BVDV on islet cells. Therefore, as BVDV did not induce IDDM in any cases, it appears that BVDV does not induce IDDM directly, but rather may be an autoimmune disease induced by autoantibodies against islet cells.     

Possible Causes of Diabetes Mellitus in Cattle Infected with Bovine Viral Diarrhoea Virus

In cattle, we encountered insulin-dependent diabetes mellitus (IDDM) associated with bovine viral diarrhoea virus (BVDV) infection. To estimate the correlation between IDDM and BVDV infection, the distribution of BVDV in the pancreas and islet-cell antibody (ICA) were investigated. The distribution of BVDV in the pancreas was examined by in situ hybridization using two oligonucleotide probes that recognized the gp25- and p14-coding regions of the BVDV gene. ICA was examined by indirect fluorescence antibody assay using the sera from affected cattle and pancreata from normal cattle. In the pancreata of all BVDV-infected cattle, including IDDM-complicated cattle, oligonucleotide probe hybridized portions were recognized. In short, BVDV genes were detected not only in IDDM-complicated cattle but also in uncomplicated cattle. Moreover, there was no hybridized portion in the islet cells. In BVDV-infected and IDDM-complicated cattle, ICA was frequently detected. On the other hand, ICA was not detected in BVDV-infected and IDDM uncomplicated cattle. These results suggest that IDDM associated with BVDV infection is not a direct effect of BVDV on islet cells. Therefore, as BVDV did not induce IDDM in any cases, it appears that BVDV does not induce IDDM directly, but rather may be an autoimmune disease induced by autoantibodies against islet cells.