Repeatability and number of measurements for productive variables in vegetable crops experiments

ABSTRACT One of the ways to optimize the evaluation of the experiment and obtain high precision of the results is with the use of an adequate number of measurements for each variable observed in the experiment. In this sense, the objective of this study was to estimate the repeatability coefficient and the number of measurements necessary for the analysis of characters of production of zucchini, cucumber, pout pepper and pea. In the experiments carried out with zucchini and cucumber the variables number of fruits, fruit mass, fruit length, largest fruit diameter and smallest fruit diameter were evaluated. For pea the number, length and mass of pods, number and mass of grains per pod and for pout pepper number and mass of fruits, largest fruit diameter and length were evaluated. The repeatability coefficient (r) was estimated by the principal component method using the correlation matrix and the covariance matrix. The number of measurements for each variable was also determined based on the coefficients of determination of 0.80, 0.85, 0.90, 0.95 and 1.00. The estimated repeatability coefficient obtained the highest estimates using the covariance matrix, ranging from 0.67 to 0.84 for zucchini, from 0.66 to 0.97 for cucumber, from 0.47 to 0.70 for pea and from 0.57 to 0.71 for pout pepper. To evaluate the fruit mass in zucchini, cucumber, pea and pout pepper, are exactly, respectively, 7, 4, 8 and 8 measurements for a coefficient of determination of 95%.

摘要 优化实验评估流程并获得高精度实验结果的有效途径之一，是为实验中观测的每个变量设置足够的测量次数。基于此，本研究旨在估算西葫芦（zucchini）、黄瓜（cucumber）、皱皮辣椒（pout pepper）及豌豆（pea）的产量性状分析所需的重复性系数（repeatability coefficient）与测量次数。针对西葫芦与黄瓜的实验中，评估变量包括果实数、果实质量、果实长度、果实最大直径及果实最小直径；针对豌豆的实验评估了荚果数、荚果长度、荚果质量、每荚粒数及粒质量；针对皱皮辣椒则评估了果实数、果实质量、果实最大直径及果实长度。重复性系数（记为r）通过主成分分析法（principal component method），分别基于相关矩阵与协方差矩阵进行估算。同时，基于决定系数取0.80、0.85、0.90、0.95及1.00的标准，确定了各变量所需的测量次数。基于协方差矩阵估算得到的重复性系数最高，其中西葫芦的估算值区间为0.67~0.84，黄瓜为0.66~0.97，豌豆为0.47~0.70，皱皮辣椒为0.57~0.71。当决定系数为95%时，评估西葫芦、黄瓜、豌豆及皱皮辣椒的果实质量所需的测量次数分别为7次、4次、8次及8次。