Repeatability, number of harvests, and phenotypic stability of dry matter yield and quality traits of Panicum maximum jacq.

ABSTRACT. Selection of superior forage genotypes is based on agronomic traits assayed in repeated measures. The questions are how repeatable the performance of individual genotypes is and how many harvests are needed to select the best genotypes. The objectives were to estimate repeatability coefficients of dry matter yield (DMY) and forage quality, their phenotypic stability and the number of harvests needed for an accurate selection. Two randomized complete block design experiments data with 24 genotypes each, undergoing 12 and 16 harvests, over a period of 2 and 3 years, respectively, were used. The DMY repeatability estimates ranged from 0.42 to 0.55, suggesting a low heritability. The mean numbers of repeated measures were 5 and 7 harvests for 0.80 and 0.85 accuracy, respectively. The inclusion of the first two harvests negatively affects the estimates. Repeatability for quality traits ranged from 0.30 to 0.69, indicating low to moderate heritability.

摘要 优质饲草基因型的选育需基于重复观测下测定的农艺性状开展。当前亟待明确的核心问题包括：单份饲草基因型的表现稳定性如何，以及筛选最优基因型所需的收割次数为多少。本研究的目标为：估算干物质产量（dry matter yield, DMY）与饲草品质的重复力、表型稳定性，以及精准筛选所需的收割次数。本研究采用两份随机完全区组设计（randomized complete block design）试验数据：每份试验分别包含24份饲草基因型，试验周期分别为2年与3年，对应收割次数依次为12次与16次。干物质产量的重复力估算值介于0.42至0.55之间，表明其遗传力较低。当筛选精度分别为0.80与0.85时，所需的平均重复观测次数依次为5次与7次收割。纳入前两次收割数据会对估算结果产生负面影响。饲草品质性状的重复力介于0.30至0.69之间，表明其遗传力处于低至中等水平。