1.The snail has given the project greater urgency.
2.Over the next year and a half investigators will test the various strains of salt-tolerant rice they've bred.
3.Each team is crossbreeding a local European short-grain rice with a long-grain Asian variety that carries the salt-resistant gene.
4.The scientists are breeding successive generations to arrive at varieties that incorporate salt tolerance but retain about 97% of the European rice genome.
arrive at （得到）
5.The giant apple snail's presence in European is limited to the Ebro Delta.
6.This sea-water also kills off the greedy giant apple snail ,an introduced pest that feeds on young rice plants.
kill off （消灭）
7.As the sea creeps into theses fresh-water marshes,however ,rising salinity is hampering rice production.
creep into （渐渐侵入）