Estimation of repeatability and genotypic superiority of elephant grass half-sib families for energy purposes using mixed models

ABSTRACT The mixed-model methodology is an alternative to select genotypes for traits highly influenced by the environment. In addition, this method allows FOR estimating the repeatability coefficient and predicting the number of assessments needed for a selection process to increase reliability. This study aimed to determine the minimum number of evaluations necessary for a reliable selection process and to estimate the variance components used for predicting genetic gains between and within half-sib families of elephant grass ( Cenchrus purpureus (Schumach.) Morrone ) using the mixed-model methodology. Half-sib families were generated using genotypes from the Active Germplasm Bank of Elephant Grass. The experiment was performed in a randomized block design with nine half-sib families, three replicates, and eight plants per plot. We evaluated 216 genotypes (individual plants) of elephant grass. The deviance analysis was carried out, genetic parameters were estimated, gains between and within families were predicted, and repeatability coefficients were obtained using Selegen software. There was genetic variability for selection within the families evaluated. The reliability values found above 60 % for plant height and number of tillers and above 80 % for dry matter yield suggest that only two evaluations are required to select superior genotypes with outstanding reliability. Sixteen genotypes were identified and selected for their productive potential, which can be used as parents in elephant grass breeding programs for bioenergy production.

摘要 混合模型法（mixed-model methodology）是针对受环境影响显著的性状开展基因型筛选的备选方案。此外，该方法可用于估算重复性系数，并预测为提升筛选可靠性所需的评估次数。本研究旨在明确可靠筛选流程所需的最少评估次数，并借助混合模型法估算象草（Cenchrus purpureus (Schumach.) Morrone）半同胞家系（half-sib families）间及家系内遗传增益预测所需的方差组分。本研究以象草活性种质资源库中的基因型为材料构建半同胞家系，试验采用随机区组设计，设置9个半同胞家系、3次重复，每小区种植8株植株，共对216份象草基因型（单株）开展性状调查。本研究借助Selegen软件完成偏差分析、遗传参数估算、家系间及家系内遗传增益预测，并计算得到重复性系数。结果显示，在所评估的家系内存在可用于筛选的遗传变异；株高、分蘖数的可靠性值均超过60%，干物质产量的可靠性值超过80%，这表明仅需开展2次评估即可筛选出可靠性优异的优良基因型。本研究共筛选得到16份具有较高生产潜力的象草基因型，可作为生物能源用象草育种项目的亲本材料。