Somatic Incompatibility in Diakaryotic-monokaryotic and Dikaryotic Pairings of Echinodontium tinctorium
Somatic incompatibility in dikaryotic-monokaryotic (di-mon) and dikaryotic pairings of Echinodontium tinctorium was investigated in vitro on 4.5% malt agar. Antagonistic reactions of varying intensity occurred in all pairings between 12 allopatric dikaryons from Idaho and Arizona, between 14 sib-composed dikaryons from two Idaho sites, and in over 95% of pairings between sympatric dikaryons from separate trees at each location. Antagonistic reactions in dikaryotic pairings macroscopically appeared as dark reaction lines in the agar and aversion zones (barrage reactions) with hyphal massing on each side of the aversion zones. Self-crosses of dikaryons were somatically compatible, and hyphal anastomoses were common. Hyphal anastomoses were rare in the aversion zones between somatically incompatible dikaryons. Somatic incompatibility occurred in 51% of 89 di-mon pairings between 29 monokaryotic isolates and 7 sib-composed dikaryons from the same parent. Somatically incompatible di-mon pairings were characterized by hyphal massing in the contact zone and reaction lines on the reverse, but they lacked barrage reactions. Clamp connections formed in 54% of all di-mon crosses and at similar frequencies when no antagonistic reactions were present (55%) or when only hyphal massing occurred (53%), but they formed less frequently (33%) when dark reaction lines were present. The potential applications of these findings to epidemiological studies are discussed.