Productive behavior of 'Williams' pear (Pyrus communis L.) grafted onto different rootstocks

The most widely used rootstocks for pears are of the genus Pyrus and Cydonia. The objective of this study was to evaluate yield and fruit quality of ‘Williams’ pear trees on different rootstocks. The experiment was conducted at the Instituto Nacional de Investigación Agropecuaria INIA Las Brujas, Uruguay. ‘Williams’ trees were planted in 2003 and evaluated during four consecutive growing seasons starting in 2014/15. Rootstocks were ‘OH×F40’ and ‘OH×F69’ (Pyrus communis), ‘BA29’, ‘EMC’, and ‘Adams’ quince (Cydonia oblonga). For quinces, ‘Beurre Hardy’ (Pyrus communis) was used as an interstem. Spacing was 4.5 m between rows, varying the space between plants, according to the expected vigor of each rootstock. For ‘OH×F40’, ‘OH×F69’ and ‘BA29’ plants were spaced 1.70 m (1,307 trees ha^‑1), ‘Adams’ 1.50 m (1,481 trees ha^‑1), and ‘EMC’ 1.30 m (1,709 trees ha^‑1). The experimental design was a randomized block with five treatments (rootstocks), and four replications. Fruit diameter, average fruit weight, flesh firmness, soluble solids content, number of fruits, and yield were evaluated. The data were submitted to analysis of variance by the F test and, when significant, the means were compared through Tukey’s test at 5%. In the 2015/16 and 2017/18 growing seasons there was low production mainly due to insufficient accumulation of chilling during the winter of 2015 and 2017, respectively. Fruit diameter and soluble solids content did not present differences among the tested rootstocks. ‘BA29’ induced higher fruit weight in comparison to ‘OH×F69’ and a firmer fruit compared to ‘OH×F69’ and ‘OH×F40’, in the 2016/17 growing season. For productivity, it was observed that ‘OH×F40’ was superior in the 2014/15 growing season, while in the 2016/17 growing season all Pyrus rootstocks were substantially superior. Results showed that Pyrus rootstocks had better performance compared to quince under optimal conditions but were less robust when climatic conditions (chill units and precipitation) were not good for pear cultivation.