PRELIMINARY INVESTIGATION OF CORRELATIONS AMONG GROWTH RATE, DIV1 RESISTANCE AND STRESS TOLERANCE OF THE PACIFIC WHITE SHRIMP Penaeus vannamei

In shrimp genetic improvement programs, fast growth, specific disease resistance and general robustness are the top  three breeding goals for consideration .  To  properly design strategies for selective breeding, it is necessary to investigate if and how these traits are genetically correlated .  The Pacific white shrimp,  Penaeus vannamei,  is the dominant penaeid species cultured , accounting for about  two-third  of  the  global production. Decapod iridescent virus 1 (DIV1) is an emerging shrimp viral disease, which is known  to affect all stages of the  Pacific white shrimp,  crayfish and giant freshwater prawn and has  caused tremendous economic loss .  As an euryhaline species, P. vannamei can survive within a wide range  of salinity , the  optimal  level for juvenile growth  is  between 15 to 25 ppt.  Hyper-saline stress test can be used  to evaluate the general robustness of shrimp.

In the study, 35 full- sib families of  Specific-pathogen-free (SPF) P. vannamei were  systemically assessed in a n eight-week growth trial, DIV1 lab challenge test and hyper-saline stress tests. Results showed that, for average initial weight of 2.5g (ranging from 1.0 to  4.0g) juvenile shrimp, the average dail y gain (ADG) of shrimp  families varied from 0.38 to 0.53 g/day,  and large between-family variations  were  detected  for both  DIV1 challenge test survival rates (SR%_DIV1 , from 8.0% to 68%) ,  and  Hyper-saline stress test  survival rates (SR%_HS, from 22% to 62% ). Phenotypic correlations between ADG and SR%_DIV1, SR%_HS were  0.0672,  -0.1026 respectively, both were  not significantly different from zero (Figure). Phenotypic correlation between SR%_DIV1 and SR%_HS was -0.3004. Further analyses revealed that such slightly negative correlation could result from the initial sizes of juvenile shrimp. The larger juveniles seemed to be more tolerant to salinity stress while the smaller juveniles tended to survive better when infected by DIV1.  Based on t he  results, a balanced index selection scheme is recommended for  the  selective breeding of P. vannamei.