Scientists have learned how to manipulate genes within a plant, a technique the biotechnology industry hopes environmentalists will like more than current genetic modification methods, which involve transplanting foreign genes into crops. The new method, made public today in two articles in the journal of the National Academy of Sciences, could let scientists tinker with the unique nutritional composition of a crop. Meanwhile, genetically engineered papaya seeds are being credited with saving Hawaii’s papaya industry from a virus that has devastated plantations in recent years. But some scientists worry the new papaya plants will lead to the creation of more potent viral diseases, and organic papaya farmers worry that their crops will be contaminated.