Crossbreeding effects for White Spot Disease resistance in challenge tests and field pond performance in Pacific white shrimp Litopenaeus vannamei involving susceptible and resistance lines

Abstract

The objective of this study was to estimate crossbreeding effects for individual survival time (STIM) in hours, and survival rate for the complete experimental period (SUEX) during challenges with White Spot Disease (WSD), as well as for individual survival rate (SURP), harvest weight at 130 days of age (HW130) and biomass production per seeded shrimp (BIOM) estimated as SURP × HW130, in commercial-like ponds with (+) or without (−) disease outbreaks in Pacific white shrimp (Litopenaeus vannamei) on the Northwest coast of Mexico. Data was obtained from 2014 to 2016 from a crossbreeding experiment involving a line of Ecuadorian shrimp with a history of WSD resistance (Resistance Line – RES) and a Mexican line with a high growth potential (Growth Line – GRO), obtained by selection for a higher growth rate in the absence of specific diseases. For challenge tests, family-marked animals were exposed per os to minced muscle tissue from WSD diseased animals and followed until mortality stabilized. Families and organisms assessed in the three years of the experimental challenges for RES, GRO and crossbreeds were 149 and 4,705, 196 and 6,186 and 144 and 4,807, respectively. Similar figures for field data were 149 and 11,490, 196 and 10,927 and 145 and 12,246, respectively. Both challenge and field data were analyzed by linear models to estimate crossbreeding effects and predicted averages for pure lines and crossbreeds. Significant direct line effects (P < 0.05) found for STIM and for SURP in all + ponds support the assumption that the RES line is more resistant to WSD than the GRO line. STIM was useful in ranking genetic groups for SURP in + ponds with an average correlation of 1.00 (P < 0.0001). The RES line had an average SURP 12.1 times that for the GRO line, and an average BIOM 16.3 times that for the GRO line in + ponds. Heterosis was positive only for HW130 (P < 0.05). The first cross between the GRO × RES lines had the highest HW130 in + ponds, while the GRO group had the highest HW130 in – ponds. As heterosis effects for BIOM were generally negative in + ponds, and loss in BIOM by using the RES rather than the GRO line is close to zero in - ponds, RES larvae could be categorized as the best alternative to minimize the risk of economic losses associated with WSD / Acute Hepatopancreatic Necrosis Disease outbreaks.