Seed Production Process Research Articles

Viral and bacterial diseases of marine fish and shellfish in Japanese hatcheries

In Japan, seed production techniques have been exploited for about 80 species of marine fish and shellfish. However, mass mortalities due to infectious and non-infectious diseases have often occurred in larvae and juveniles reared in marine hatcheries. Among these problems the viral and bacterial diseases with their control measures are reviewed in this paper. Since around the middle of the 1980s, viral diseases such as viral epidermal hyperplasia (herpesvirus infection) in the Japanese flounder, viral ascites (birnavirus infection) in yellowtail, viral nervous necrosis (VNN) (nodavirus infection) in Japanese parrotfish and striped jack, and baculoviral mid-gut gland necrosis (BMN) (baculovirus infection) and penaeid acute viremia (PAV) (unclassified virus infection) in kuruma prawn have been reported. It was demonstrated that the selection of virus-free spawners based on the detection of the pathogen by polymerase chain reaction (PCR) serves as an effective control measure against vertical transmission of the pathogen in VNN and PAV. Vibriosis, pasteurellosis, gliding bacterial infection and other bacterial diseases have occurred in various marine fishes at their juvenile stages. On the other hand, larval fish most frequently develop intestinal infections represented by bacterial enteritis with Vibrio ichthyoenteri in the Japanese flounder. In the last part of the article, control measures for viral and bacterial diseases were discussed in each step of seed production process.

Use of molecular marker techniques in seed testing by Brazilian seed companies

Seed market is becoming global and globalization is growing very fast. To compete favourably in this new global seed world, quality and cost are and will be certanly the key issues. High seed quality can only be obtained by a thorough control of the entire seed production process, step by step from planning to final delivery. That requires science, technology, expertise, experience, good management and certanly, the most important, an absolute and unconditional commitment with quality. Seed testing for quality assurance is one important step in the process of production of high quality seed. In the late years a considerable amount of research has been published, particularly on the use of some Polymerase Chain Reaction DNA based new technologies (RAPD, microsatelites, AFLP) for genetic purity determinations in seed testing. As far as we know, no Brazilian seed company is using, on regular basis, RAPD or other molecular marker techniques in the determination of genetic purity in seed testing. Most of these are using morphological or physiological traits expressed by seed, seedling or mature plant and/or electrophoresis of seed or seedling proteins/isoenzymes for that purpose. Main reasons for that are: DNA molecular marker techniques are relatively new; lack of specialized personnel to run DNA molecular marker assays on routine basis; higher cost/sample when compared to proteins/isoenzymes electrophoresis.

数種餌料で培養したワムシのガザミ幼生に対する餌料価値

Larvae of swimming crab were reared in 1-2 l tanks, supplied with marine rotifers cultured with several feeds: baker's yeast, baker's yeast fortified with cuttlefish liver oil, freshwater Chlorella, and marine micro algae Nannochloropsis. The fatty acid compositions of the rotifers were analyzed to evaluate their dietary value. Larval survival, growth and velocity of development were improved according to the amount of n-3 highly unsaturated fatty acids (n-3HUFA) contained in rotifers. Consequently, it was considered that the larval swimming crab demanded the n-3HUFA in feeds as essential fatty acid and enrichment of feed rotifers should be a routine technique in the seed production process of the swimming crab.

Identification of triplex (YYYy) Potato Virus Y (PVY) immune progenitors derived fromSolanum tuberosum ssp.andigena

As part of the International Potato Center’s (CIP) virus resistance breeding strategy, a group of 182 selected clones from intercrosses among duplex Potato Virus Y (PVY) immune progenitors derived fromSolanum tuberosum ssp.andigena (i.e., YYyy × YYyy) was sampled. These clones were test-crossed to the PVY susceptible tester 377964.5 (yyyy) to search for triplex (YYYy) and quadruplex (YYYY) PVY immune potato progenitors. Seedlings of each test-crossed progeny were screened for PVY immunity. Genetic analysis of observed ratios for immunity-susceptibility showed that two of the 182 clones segregated as triplex under the assumption of a random chromatid segregation model. The double reduction coefficient, α, and its standard error were estimated from the experimental data, and had values of 0.1566 and 0.0186 respectively. These results indicated that crossovers take place during meiosis between the locus and the centromere, permitting sister chromatids to migrate to the same pole producing a random chromatid segregation. In the population evaluated, no clone was identified as a quadruplex. The two triplex PVY immune genotypes will produce about 96% of progenies with PVY immunity when mated to PVY susceptible advanced clones or varieties. These progenitors have the potential to provide a durable PVY genetic control and diminish the present impact of this virus on the potato crop. Also, immunity to PVY will significantly simplify the seed production process.

Neutralizing Monoclonal Antibodies to Striped Jack Nervous Necrosis Virus (SJNNV).

Viral nervous necrosis (VNN) caused by a nodavirus (striped jack nervous necrosis virus : SJNNV) is a serious problem in seed production process of striped jack Pseudocaranx dentex in Japan. Mouse monoclonal antibodies (MAbs) to SJNNV were produced by using a homogenate of infected larval striped jack. Among 8 MAbs reacting with the homogenate of infected larvae in enzyme-linked immunosorbent assay (ELISA), three MAbs (SJ-102B, SJ-204D, SJ-207C) were proved to recognize the 42 kDa coat protein of SJNNV by Western blot analysis. An in vivo neutralization test, where larval striped jack were exposed to purified SJNNV (100ng/ml) or the virus treated with MAbs (1mg) and the resultant infection with SJNNV in larvae was monitored by ELISA using an anti-SJNNV rabbit serum, exhibited that two MAbs SJ-102B and SJ-204D have neutralizing activity against SJNNV.