The authors developed acid-resistant egg sheet with resistance to hydorchloric acid treatment. Acid resistance was conferred by treating the paper with shellac derived from the lac bug. To produce acid-resistant egg sheet, commercial paper was soaked in a shellac-ethanol solution (30g/L), dried and then heat-treated in a drying oven at 140°C for 30min.
In sericultural farms, Bombyx mori nucleopolyhedrovirus (BmNPV), a causal agent of the inside-stained cocoon problem, would be mainly distributed in the mounting room. We revealed this fact by a classical method of the “dust feeding bioassay”, often used in the epizootiological research for the silkworm viruses. In 2003, dust samples of 13 to 16 sericultural farms located in southern area of Ibaraki, Japan, were collected from the rearing room, mulberry stock room, mounting room and entrance of the farmer’s house immediately before the spring rearing and just after the spring, summer, early-, and late-autumn cocoon harvest, and then bioassayed with artificial diets using B. mori second instar larvae to detect BmNPV. The initial survey, immediately before the spring rearing in May, revealed that BmNPV was dispersed around the farming area and mainly detected from the mounting rooms in 8 of 13 farms. The BmNPV distributional traits just after the cocoon harvest each season also suggested that the mounting room was the most contaminated with BmNPV. In September 2013, ten years later from the first survey, we reconfirmed the BmNPV accumulation in a mounting room of a sericultural farm located in Tochigi, Japan, where the cocoon yield was heavily damaged by a nucleopolyhedrosis in the early autumn season. According to a series of our surveys, the mounting room would be the most important place for the BmNPV control strategy in the sericultural farm.
BL, the parent of “Platina boy”, is a balanced sex-limited lethal and sex-limited moricaud silkworm, which has two chromosome fragments attached to W chromosome. It was analyzed by using the probes from RFLG1 (= Z chromosome) or RFLG19 (= second chromosome) on the molecular linkage map of silkworm. In Southern blotting hybridization, signal intensities were essentially equal between female and male, only when m47 clone on the RFLG1 was used as a probe, but not with other two clones, suggesting that W chromosome in the strain BL has an attached fragment of Z chromosome including the rejoin of m47. On the other hand, any of the four RFLG19 probes did not exhibit significant difference in pattern and intensity of the signals between sexes. It is likely that the attached fragment contains pM gene is so smaller than expected that these probes detected homologous sequences located only to the normal second chromosomes. In conclusion, it was suggested that BL could be identified by RFLP analysis with the clone which was included in the attached chromosome fragment. Therefore, this discrimination method by RFLP for the sex-limited strains is accurate and easy in contrast with the test by rearing. It also revealed the possibility of developing an easier discrimination method for the silkworm races by utilizing the genome information of the silkworm.
To clarify the contamination status of Bombyx mori nucleopolyhedrovirus (BmNPV) on cocoon harvesters, usability of PCR techniques in epizootiological research for the silkworm virus was investigated by using BmNPV-specific primers based on the major capsid Bp 39 gene region reported by Lu and Iatrou (1996). In the first stage PCR using a primer pair, Bp 39-1F and -2R, sensitivity and reproducibility of the primer pair to the BmNPV from occlusion bodies (OBs) were restricted in the amplification of the viral DNA from 102 OBs per 20μl of PCR reaction mixture. Application of nested-PCR using a primer pair, Bp 39-3F and -4R after the first PCR, enhanced sensitivity and reproducibility of the amplification of the target sequence of Bp 39 gene region from the viral DNA from 1-10 OBs. Using dust samples from cocoon harvesters collected by gauze wiping method devised in this study and applying the above PCR techniques, contamination status of BmNPV on six cocoon harvesters of sericultural farms was clearly distinguished. This technique could be applicable in estimating the BmNPV dispersal and contamination status on various structural objects of sericultural farms in the future research.