What is the current state of technology development in China's walnut industry?

  1. Walnut variety breeding

  China's walnut crossbreeding began in the mid-to-late 1960s, with outstanding results from research institutions such as the Liaoning Institute of Economic Forestry, the Shandong Academy of Agricultural Sciences Pomology Institute, and the Chinese Academy of Forestry. Using common walnut (Juglans regia) as the crossbreeding parent, they successively bred excellent varieties such as Liaoning No. 1, Zhonglin No. 1, and Xiangling. In 1990, upon appraisal by the Ministry of Forestry, 16 new early-bearing walnut varieties were evaluated as China's first batch for promotion, becoming the main force in the current improved-variety drive for walnuts.

Pictured: walnut

  2. Propagation technology

  Before the 1980s, walnut propagation in China was mainly seed-based. With seed propagation of walnut under natural pollination, the offspring vary greatly, individuals often show phenotypic differences, and they bear fruit late, so it can no longer meet production needs. At present, graft propagation is the main means of achieving improved varieties and early fruiting with high yields.

  Depending on the scion used, walnut grafting is divided into two major categories: branch grafting and bud grafting. Walnut bark-insertion tongue grafting is currently recognized as the branch grafting method with the highest survival rate, generally reaching more than 80%. This has promoted the widespread application of top grafting for variety replacement in production. With the successful use of techniques such as early insertion of rootstock and multiple successive collections of scions in walnut bud grafting, the survival rate now reaches more than 95%, greatly advancing the pace of walnut variety improvement.

  3. Tree management

  Walnut tree shape is best as a central-leader delayed-open form or a natural open-center form. Training should generally be done early rather than late, with the requirement that it be basically completed within 5-7 years. The main task of pruning young fruiting trees is to develop scaffold branches at all levels so they quickly form a good tree framework. The main task of pruning trees in full bearing is to promptly adjust and balance tree vigor, regulate the contradiction between growth and fruiting, and extend the years of full bearing. The task of pruning aging trees is to renew and rejuvenate the canopy using water sprouts and newly grown branches. Research results on high-yield cultivation techniques for young walnut trees show that young trees should be pruned; otherwise, early-bearing varieties are prone to premature aging, directly affecting yield.

  4. Pest and disease control

  At present, more than 120 species of insect pests and more than 30 diseases are known to harm walnuts. Nationwide, the types, distribution, and severity of pests and diseases vary from place to place. Walnut pests and diseases directly affect walnut yield and quality and have attracted widespread attention.