Evaluation of Pyrus and Quince Rootstocks for High Density Pear Orchards

Abstract

High density planting systems are a prerequisite to economise the use of land and labour costs of orchards. Dwarfing rootstocks controlling the vigour of the scion cultivars form the basis for such orchards (Wertheim and Webster, 2005). In the Netherlands, rootstock research is limited to and focussed on testing rootstocks selected abroad. For the Dutch pear growers the main selection criteria for new rootstocks are: 1) control of tree size; 2) production; 3) fruit size; 4) fruit quality; 5) production efficiency; 6) frost resistance. Additional criteria for Dutch fruit tree nurseries exporting trees to other countries are: 1) compatibility with scion cultivars; 2) suitability for growth in calcareous soils; 3) easy propagation. In all trials rootstock performance is compared to Quince MC, the most commonly used rootstocks for pears in the Netherlands. Recently, a number of Pyrus (Pyrus communis) and Quince (Cydonia oblonga) rootstocks have been tested with 'Conference' and 'Doyenné du Comice' as the scion cultivars. Generally, the production efficiency of the Pyrus rootstocks was much less than for Quince MC. Another disadvantage of the evaluated Pyrus rootstocks was their high sensitivity towards pear decline. Several rootstocks were rejected after examination of the graft union because of suspected compatibility problems. Of the tested Quince rootstocks C 132 shows promise because of its control of tree growth in combination with good fruit size and Eline ® because of its reduction of fruit russeting in 'Conference'. INTRODUCTIONHigh density planting systems are the starting point of modern orchards. Small trees that come into production in the second year after planting are a prerequisite to achieve regular yields of high quality fruits and to economise the use of land and labour costs for pruning and picking. Dwarfing rootstocks, controlling the vigour of the scion cultivars and inducing precocity of cropping, form the basis for such high density orchards.European pears are predominantly grown on rootstocks of Quince (Cydonia oblonga). In the Netherlands, the majority of pears are grown on Quince MC, but Quince MA and Quince Adams are also used. 'Conference' is the most important cultivar. Grown in high density planting systems yearly yields of 60 to 70 tons/ha are feasible. To obtain this production level a good control of shoot growth, flower bud development and fruit set is required.Although Quince MC has been used successfully for many decades in the Netherlands, there are several reasons to look for alternative rootstocks. Until 2001, the growth retardant chlormequat (CCC) was used the reduce shoot growth and stimulate flower bud development. The withdrawal of CCC for use by fruit growers has renewed the interest in rootstocks more dwarfing than Quince MC. Besides dwarfing of the scion cultivar other desired traits of new rootstocks for pears are: 1) precocity of cropping, to ensure early yields starting in the second year after planting; 2) fruit size, for 'Conference' pears the proportion of ...

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