Growth and fruit yield of seedlings, cuttings and grafts from selected son tra trees in Northwest Vietnam

Abstract

This study examined tree growth and fruit production of son tra (Docynia indica), an indigenous fruit tree. Eight phenotypically superior trees with high fruit yields and good fruit appearance were selected in 2005 at Ngoc Chien commune, Muong La District, Son la Province, Northwest Vietnam. Three types of planting material were raised from these trees: grafts from the selected trees onto unselected seedling rootstocks, seedlings raised from seeds collected from the superior trees and cuttings raised from seedlings. The grafts, seedlings and cuttings were planted out in 2006 in adjacent blocks in a field trial established at Chieng Bom experimental station in Son La Province. Thirty trees of each type were monitored for a 3-year period commencing in January 2012, when the trees were 6 years old. Survival of all three types from planting was excellent, remaining above 90% at the end of 2014. Grafted trees grew fastest, attaining a mean height of 7.0m and crown width of 4.4m, while trees raised from cuttings grew significantly slower (height 5.0m and crown width 3.4m, with seedlingderived trees intermediate. Mean fruit yield at 8 years was significantly higher for grafts (38.7kg per tree) compared to trees raised from seedlings (30.7kg per tree) and those from cuttings (28.9kg per tree). Fruits from the grafted trees were judged to be of superior quality, being predominantly yellow in colour and of uniform large (> 3cm) size, while fruit from most of the seedling and cutting-derived trees were judged to be of moderate quality with inferior size and colour. Considering the excellent survival of grafts and their superior fruit yield and fruit quality, grafting can be recommended as a better way to propagate selected son tra trees, compared with using seedlings raised from seed collected from the selected trees or cuttings raised from these seedlings