Worldwide, farmers are weighing whether to change their planting patterns and grow more wheat this spring as the war has choked off or thrown into question grain supplies from a region known as “the breadbasket of the world.” Ukraine and Russia account for a third of global wheat and barley exports, which countries in the Middle East, Asia and Africa rely on to feed millions of people who subsist on subsidized bread and bargain noodles. They are also top exporters of other grains and sunflower seed oil used for cooking and food processing.