GENETIC SUSCEPTIBILITY OF CULTURED SHRIMP (PENAEUS-VANNAMEI) TO INFECTIOUS HYPODERMAL AND HEMATOPOIETIC NECROSIS VIRUS AND BACULOVIRUS-PENAEI - POSSIBLE RELATIONSHIP WITH GROWTH STATUS AND METABOLIC GENE-EXPRESSION

Offspring of four crosses (I, II, III, and IV) of Penaeus cannamei fro m known high-and low-growth families were challenged with infectious h ypodermal and hematopoetic necrosis virus (IHHNV) and Baculovirus pena ei (BP) to compare their susceptibility to these viral agents and exam ine the genetic component involved in disease resistance or susceptibi lity. Family crosses were made using broodstock from five families dev eloped by the U.S. Marine Shrimp Farming Program. The prevalence of IH HNV infection was highest in cross I and lowest in cross III. Cross I was developed using male and female broodstock from the low-growth fam ily 1.6, and cross III was developed using a female from the high-grow th family 1.3 and a male from the low-growth family 1.6. The prevalenc e of BP infection at Day 4 was highest (100%) in cross IV which was de veloped using a female from the low-growth family 1.4 and a male from the high-growth family 1.5. The reciprocal cross, cross III, had the l owest (68%) prevalence at Day 4 postexposure, Both crosses I and LI ha d 88% prevalence of infection at Day 4. Despite 100% prevalence of BP infection in cross nr at 4 days, animals from this cross and cross II exhibited high survival by Day 18 (85 and 77%). On the other hand, cro sses I and III (with 88 and 68% prevalence at Day 4, respectively) sho wed low survival at Day 18 (19 and 24%). On the basis of prevalence of infection and mortality rates, it was concluded that the susceptibili ty to BP in penaeid shrimp is governed by the genetic background of th e parental crosses. The random amplified polymorphic DNA polymorphisms for crosses I, II, III, and TV, were 43, 45, 53, and 51%, respectivel y, showing no clear relationship between IHHNV and BP prevalence of in fection and levels of nuclear genetic diversity Though the mtDNA haplo types in offspring from the different crosses were the same, major dif ferences were observed in both steady-state levels and patterns of exp ression of the mitochondrial 12s rRNA in offspring obtained at various early developmental stages from each of the four crosses. The possibl e relationship among disease susceptibility growth status, and express ion of mitochondrial 12s rRNA is discussed in the context of a complex nuclear-cytoplasmic genetic system involved in the regulation of gene expression. (C) 1997 Academic Press.