Growth and Cropping of 'AU-Super' or 'Eaton' Chestnut Trees with 'Little Giant' Interstem on AU-Cropper Seedling Rootstock

Abstract

Chestnut (Castaneasp.) scion cultivars, 'AU-Super' and 'Eaton', with or without 'Little Giant' interstem on AU-Cropper seedling rootstock, were grafted in 2005 and planted in 2006 near New Franklin, MO to evaluate tree survival, vegetative growth, and nut yield for eight growing seasons. Tree survival in 2013 was 100% for each cultivar/interstem combination, except for 'AU Super' with 'Little Giant' interstem which had a 22% loss due to delayed graft union failure. 'Little Giant' interstem reduced tree height and trunk cross-sectional area (TCA) of 'AU-Super' trees by 0.7 m and 57 cm ², respectively, but did not affect height or TCA of 'Eaton' trees. Trees of both cultivars with or without the interstem exceeded their allotted 4 m in-row spacing in 2012. Trees of three scion/interstem combinations produced a few chestnuts in 2008, whereas 'Eaton'/'Little Giant' interstem trees began cropping in 2009. The largest annual increase in nut yield per tree for all scion/interstem combinations was in 2012. Average nut weights for all trees were greatest in 2010, but were reduced thereafter. By 2013, 'AU-Super' trees had greater cumulative yield than 'Eaton' trees, but it was not affected by the interstem for either scion cultivar. Cumulative yield efficiency was similar for cultivars with or without interstems. Thus, 'Little Giant' interstem grafted to scion cultivar 'AU-Super' and 'AU-Cropper' rootstock had a slight dwarfing influence on trees and did not adversely affect cumulative nut yield from 2008 to 2013. However, as cropping generally increased, average nut weights for all cultivar/interstem combinations were substantially reduced in the sixth growing season and remained low through 2013.