凡纳对虾不同品系生长和急性肝胰腺坏死病抗性遗传参数估计

Estimation of genetic parameters for growth and acute hepatopancreatic necrosis resistance in different strains of Penaeus vannamei

中文关键词: 凡纳对虾  生长  AHPND抗性  遗传力  遗传相关

英文关键词: Penaeus vannamei  Growth  AHPND resistance  Heritability  Genetic correlation

中文摘要:

      为开展凡纳对虾(Penaeus vannamei)生长和急性肝胰腺坏死病(acute hepatopancreatic necrosis disease, AHPND)抗性复合选育，本研究以自主选育的凡纳对虾高抗和快大品系为研究对象进行生长和AHPND抗性测试。实验家系共计70个(高抗家系40个，快大家系30个)，实验个体共计1 760尾(高抗个体800尾，快大个体960尾)。2个品系分2批次进行VpAHPND定量口饲感染。批次内实验个体达半数死亡后停止投喂毒饵。利用个体动物模型和父母本阈值模型评估2个品系3 个性状(体重、感染VpAHPND后个体存活时间、家系半致死存活率)的遗传力；利用两性状动物模型评估3个性状两两之间的遗传相关。结果显示，高抗系体重遗传力估计值为0.599±0.120，为高遗传力水平；个体存活时间遗传力估计值为0.240±0.072，为中等遗传力水平；家系半致死存活率遗传力估计值为0.173±0.051，为低等遗传力水平。快大系体重、个体存活时间和家系半致死存活率的遗传力估计值分别为0.266±0.082、0.374±0.096、0.257±0.048，均为中等遗传力水平。经Z-score检验，2个品系各性状遗传力估计值与0差异均达到极显著水平(P<0.01)。2个品系内的体重与AHPND抗性性状(个体存活时间、家系半致死存活率)遗传相关均表现为低度正相关(0.061~0.235)，且与0差异不显著(P>0.05)；2个品系内的个体存活时间与家系半致死存活率遗传相关分别为0.997±0.129、0.967±0.044，为高度正相关。结果表明，在实际选育过程中，可将生长和AHPND抗性作为选育指标纳入综合选择指数进行选种制种；为简化抗性测试过程，可将家系半致死存活率作为选育群体的AHPND抗性指标。本研究为开展凡纳对虾生长和AHPND抗性优良品种的选育提供了参考。

英文摘要:

      The Pacific white shrimp or white leg shrimp, Penaeus vannamei, is native to the tropical coastal regions of Central and South America. It is one of the three major shrimp species with high production worldwide. It was brought from Hawaii, USA, in 1988 and introduced into China. It has been widely promoted and cultivated due to its adaptability to the environment, fast growth rate, and suitability for high-density industrial farming. As of 2022, China's total production of P. vannamei reached 2.09 million tons, accounting for >90% of the country's total shrimp farming production. It has become one of the pillar industries in China's aquaculture sector. With the continuous expansion of aquaculture, diseases are becoming increasingly severe. Among them, acute hepatopancreatic necrosis disease (AHPND) hinders the development of the global shrimp farming industry and causes catastrophic economic losses. After infection, most shrimp show hepatopancreatic enlargement, which appears pale white or light yellow. In the later stages of infection, some diseased shrimp may exhibit atrophy of the hepatopancreas, appearing reddish-brown and blackened, with a hardened texture. Within 20–30 d after infection, death can occur, with a mortality rate of up to 90%. As of 2021, the economic losses caused by this disease to the major P. vannamei farming areas (China, Malaysia, Thailand, Vietnam, and Mexico) have exceeded 43 billion US dollars. Cultivating novel P. vannamei germplasm with AHPND resistance is an effective way to solve AHPND. Recently, domestic researchers have established independent shrimp breeding systems and cultivated 12 novel P. vannamei strains, such as "Hai Xing Nong No.2", "Ren Hai No.1", and "Zheng Jin Yang No.1". These varieties mainly target traits such as growth, resistance to white spot syndrome virus, farming survival rate, and temperature, salinity, and ammonia nitrogen tolerance. However, no reports of novel varieties specifically targeting AHPND resistance are available. Growth traits are essential economic traits in the genetic breeding of aquatic animals. Among the 12 novel P. vannamei varieties in China, 11 have excellent traits related to growth. Evaluating the genetic relationship between growth and AHPND resistance in the core breeding population of P. vannamei is important for fully utilizing existing high-quality germplasm and breeding novel varieties with composite traits and AHPND resistance. Genetic parameters reflect the genetic variation of target traits in a breeding population and are important references for breeding decisions. Due to the complex genetic background of existing P. vannamei germplasm resources in China, genetic parameters are influenced considerably by the tested population, infection methods, and other factors. Before breeding, stable infection tests must be conducted on the base population and obtain accurate parameters. This study used two independently bred P. vannamei strains as research objects to test their growth and AHPND resistance. Among them, 40 families were selected for high resistance (20 individuals per family, total 800 experimental individuals), and 30 families were selected for fast growth (32 individuals per family, total 960 experimental individuals). The test was conducted at P70–P90 by feeding with VpAHPND quantitative oral infection. Feeding with toxic bait was stopped after 50% of the experimental individuals died. The genetic heritability and correlation of the weight, individual survival time after VpAHPND infection, and half-lethal survival rate of the two strains were evaluated using individual animal and male and female threshold models. The results showed that the weight heritability estimate of the highly resistant strain was 0.599±0.120, indicating a high level of genetic heritability. The heritability estimates of survival time and half-lethal survival rate were 0.240±0.072 and 0.173±0.051, respectively, indicating a moderate to low level of genetic heritability, and all significantly different from 0 (P<0.01). The weight heritability estimate of the fast-growth strain was 0.266±0.082, indicating a low level of genetic heritability. The heritability estimates of survival time and half-lethal survival rate were 0.374± 0.096 and 0.257±0.048, respectively, indicating a moderate level of genetic heritability, and all significantly different from 0 (P<0.01). The genetic correlation between weight and AHPND resistance traits (survival time and half-lethal survival rate) in both strains showed a low positive correlation (0.061–0.235), and no significant difference was observed from 0 (P>0.05). The genetic correlation between survival time and half-lethal survival rate in both strains was highly positively correlated, with estimates of 0.997±0.129 and 0.967±0.044, respectively. The results indicate that growth and AHPND resistance can be included as selection indicators in the comprehensive selection index for breeding and seed production in the actual breeding process. Under limited conditions, the infection program can be simplified, and the half-lethal survival rate can be used as the AHPND resistance indicator for the breeding population. This study provides a primary reference for utilizing existing germplasm resources to develop high-quality P. vannamei strains for growth and AHPND resistance breeding.