Crop yield response to water - Cra

Lead AuthorSAmos Naor(GRI, University of Haifa, andMigal - Galilee TechnologyCenter, Israel)Joan Girona(IRTA, Lleida, Spain)Contributing AuthorsHussein Behboudian(Massey University, Institute ofNatural Resources, PalmerstonNorth, New Zealand),Robert G. Evans(USDA-ARS, Sidney,Montana, USA)Jordi Marsal(IRTA, Lleida, Spain)AppleIntroduction and BackgroundApple (Malus domestica Mill.) is one of the most widely cultivatedfruit crops and is produced commercially in over 80 countriesaround the world (FAO, 2011). Its production is the third highestfruit crop in the world after banana and grape and is ranked secondbehind grape for area. Most apples are grown in temperate zones becauseof the high chilling requirements for proper bud break in the spring. Thedevelopment of apple varieties with low chilling requirement and theuse of dormancy‐breaking chemicals has enabled the migration of applestowards warmer regions. Production areas have increased significantlyin recent decades until 2000, when China took the lead in production.Total production of apples stabilized during 2000-2010 at 60 to 70 milliontonne/ year. In 2009, the harvested area exceeded 4.9 million ha with anaverage yield of 14.7 tonne/ha (FAO, 2011). Figure 1 shows the productiontrends of the principal countries. China is the largest apple-producingcountry (42 percent of world production) and its production is six-foldlarger than the second country (United States, 7 percent).The duration of the season from bud break to harvest varies widely amongvarieties, from 70 days up to 210 days (Westwood, 1993) and it is correlatedwith the storability duration.Apple originated in Central Asia, where its wild ancestor is still foundtoday. There are more than 7 500 known cultivars resulting in a wide‐rangeof fruit characteristics. Cultivars vary in their yield, fruit size, colour, taste,and the ultimate size of the tree, even when grown on the same rootstock.Apple is grown in a wide‐range of environments, in many areas of Asiaand other continents. In Europe from Scandinavian countries in the northto Italy in the south, in South Africa, Australia and New Zealand, UnitedStates and Canada, and in the southern countries of South America. Theoptimum climatic requirements might be characterized as cool to coldwinters followed by a rapid rise in temperature in spring.Apple has two types of buds, pure vegetative and mixed buds containinga floral bud that has several vegetative buds at its base. The floral budgenerates an inflorescence that usually has five flowers. Flower buds areborne terminally on shoots and spurs and, to some extent, on lateral budsof one year-old shoots. Most apple varieties have self-incompatibility(Goldway et al., 2007) thus growers usually include more than one varietywithin each plot, and some orchard growers use crab apples as pollinators.332crop yield response to water