PARIS (Reuters) -Rain in large parts of France overnight provided some relief but not enough for cereals suffering a prolonged drought, the head of the France’s largest farm union said on Monday. Dry weather in France, the European Union’s biggest grain producer, has added to market worries about global supply due to war disruption in Ukraine, a major grain exporter. A heat wave harming crops pushed India to ban wheat exports on Saturday. FNSEA chief Christiane Lambert said on BFM television that the bone-dry soil prevented crop from absorbing much of the rain. “The situation is very complicat…