Genetic variation in a sorghum line with multiple genetic instability induced with ethidium bromide in an in vitro culture

Ethidium bromide treatment (15 mg/l, 26A degrees C, 18 h) of a sorghum Zheltozernoe 10 callus culture yielded line Zh10-br1 displaying multiple genetic instability. The line was characterized by a broad variety of mutations, which were identified in consecutive generations obtained from one initial regenerant via self-pollination. The mutations caused male sterility (male sterility, generation R-1), a low plant height (dwarfness, R-2), a reduced awn length (awnless, R-3), yellow leaves in seedlings (xantha, R-6), leaf variegation (leaf variegation, R-6), leaf bleaching (virescence, R-6), etc. In some cases, segregation in families suggested a monogenic recessive inheritance for the induced mutations. Male sterility was due to a range of defects that affected microsporogenesis and microgametogenesis and were probably caused by mutations of several genes. Leaf variegation was due to the appearance of green sectors in originally albino seedling leaves; the reversion occurred only in somatic tissues without affecting male and female gametes. In male-sterile and variegated mutants, sequence-specific amplified polymorphism analysis with primers to the Isaak transposon revealed new DNA fragments, which were absent from the original line. The results supported the hypothesis that the mutations isolated in line Zh10-br1 result from transposon mobilization induced by ethidium bromide and/or in vitro culture conditions.