Fenotipagem de rachaduras em clones de Eucalyptus spp.

Abstract

Eucalyptus is, currently, the most studied wood in the treated wood market due to its innumerous advantages, such as rapid growth, good shape, good market acceptance, and easy reproduction. However, there are a few limitations to eucalyptus in this segment. Primarily, the rapid growth of trees can cause internal tensions in the living tree, called growth tensions, which lead to the appearance of splits in the logs. Consequently, the physical and profitable performance of the product decreases for specific uses. The log-splitting index is the main assessment used to select clones for the treated wood segment in breeding programs by manual measurement. However, this procedure is highly time-consuming to analyze several clones at once. Thus, the present work aimed to compare end split log phenotyping methodologies in terms of efficiency and time spent in clone selection. For this purpose, the evaluation methodologies were used through manual, visual (per score), and image measurements. A total of 32 clones selected by volume were used in an expanded clonal test planted in two spacings (3 x 3 and 3 x 5 meters). Two trees from each clone were cut from each spacing for sampling. The samples consisted of one meter each, collected at four heights (0%, 25%, 50%, and 75% of the commercial height). The selective accuracy was considered very high for the three methodologies (above 96%), demonstrating genetic variability for end split logs in the population. The coincidence index between phenotyping methodologies was 71% when a selection intensity of 12.5% was applied. In other words, three of four selected clones coincided. The estimates of the Spearman correlation coefficients between the methodologies showed positive values of high magnitude. Therefore, all three methodologies were efficient for assessing end split logs. However, the time and resources spent on manual evaluation were much higher than on visual and photographic assessments, indicating that the use of the last two evaluations is preferable.