Sexual hybrids of Azolla filiculoides with A. microphylla

Abstract Sexual hybrids of Azolla microphylla with A. filiculoides were reported previously. The reciprocal cross—A. filiculoides with A. microphylla was made. Among 114 crosses, eventually 9 populations survived. Hybridization was confirmed by the isozyme patterns and monoclonal antibody specific to cyano-symbiont of A. filiculoides. One of them (IRRI Accession No. FI 1064) was found to be non-hybrid. Five strains (FI 1066–1070) grew poorly and were pale green at the initial stage of the sporophyte growth with symbiotic cyano-bacteria inside and outside leaf cavities. Cyano-symbionts eventually entered in the leaf cavities, or lost (FI 1070). Three strains (FI 1062, FI 1063, FI 1065) grew apparently normally, but two of them were devoid of cyano-symbionts (FI 1062, 1063). Strain FI 1065 grew as good as both parents at 26/18°C, but strains FI 1066–1069 produced 50% less biomass than both the parents. Their acetylene reduction activity was 20% less than the parents, resulting in the higher N contents than ...