Clonal selections of 'Williams' pear in Uruguay

Fruit quality of ‘Williams’ pear produced in different Uruguayan commercial orchards presents some variability. It is difficult to understand if these differences are due to environmental or genetic (different accessions) factors linked to the source of plant material used for propagation. To investigate if there are genetic differences among them, this research intended to evaluate the phenotypic characteristics of different sources of ‘Williams’ pear accessions under the same growing conditions. The trial was carried out in 2007 at INIA Las Brujas, Canelones, Uruguay. Quince ‘Adams’ was used as rootstock with an interstem of ‘Beurré Hardy’. The treatments were different sources of ‘Williams’ (17 possible accessions in total), with four repetitions. At harvest, yield and fruit number were analyzed. In addition, the fruit variables equatorial diameter, length, length/diameter ratio, weight, and epidermis quality as represented by lenticel prominence, skin texture and presence or absence of russet were determined. Data were statistically separated with analysis of variance and the means of treatments were grouped by the use of Scott-Knott test (p≤0.05). The Unweighted Pair-Group Method using Arithmetic averages (UPGMA), a multivariate technique, was used for cluster analysis. Yield and fruit number showed significant differences; accessions 1, 3, and 13 presented the highest yields, mainly for the last harvest seasons. That could be related to low chilling accumulation in recent years, indicating differences among the accessions in their adaptation to mild winter conditions. Significant differences among accessions were found for the following variables: fruit diameter, fruit length, as well as length/diameter ratio. Concerning the epidermis quality parameters, differences were also observed, highlighting accessions 8 and 13. This confirms that the different behavior originally observed in the different locations was not due to site conditions. There are accessions performing better under the Uruguayan pear growing conditions, which show a potential to improve new orchard plantings.