Walnut Genotypes for High Density Orchards

The aim of this review is to check the possibilities and circumstances regarding how to create a high-density Persian walnut orchard. Increasing yields, decreasing tree size, limiting juveniles, and lowering total costs are the most important objectives of breeders and horticulturists. Reducing the size of walnut trees can increase yield. Breeding programs in several countries have led to the production of walnut dwarf rootstocks. For example, Daixiang and Daihui in China, Alvand in Iran, and Fernette in France are all novel-bred dwarfing Persian walnut rootstocks. These precocious walnuts are considered to be a rare resource in the study of precociousness as well as juvenile and flowering mechanisms. Moreover, they play a potential role in breeding and modifying cultivars by genetic engineering, through walnut ameliorating programs. The CRISPR (clustered regularly interspaced short palindromic repeat) technique is used to improve walnuts, which will be used in the near future.