Nodulation and nitrogen fixation mutants of pea, Pisum sativum.

The 36 mutants which did not nodulate and 24 mutants which formed inefficient nodules with no or very low acetylene reduction activity were isolated among 86,000 M2-seedlings of 'Finale' pea, Pisum sativum L., after treatment with chemical mutagens. One mutant was found for approximately every 50 chlorophyll mutants. Most mutations were induced by ethyl methanesulfonate; some by diethyl sulfate, ethyl nitrosourea and acidified sodium azide. Putative mutants were selected as nitrogen deficient plants, yellowing from the bottom and up, when M2 seedlings were grown in sand with a Rhizobium mixture and PK fertilizer. The mutants were verified in the M3 generation by acetylene reduction assay on intact plants.