Inheritance of Some Genetic Markers in Cochliobolus Sativus

Pseudothecia of Cochliobolus sativus (Ito and Kurib.) Drechsl. ex Dastur have not been reported in nature but they usually develop in culture when sexually compatible isolates are mated under appropriate environmental conditions (10, 13). Sexual compatibility is controlled by a pair of alleles (A and a) and the two mating types appear widely distributed in nature (2-5, 10). Previous studies have examined the genetic control of several attributes, including sporulation (14), inherent germinability of conidia in soil (1), pathogenicity to grass species (6), colony morphology, virulence to wheat and barley cultivars, and blocks in sexual reproduction (3). White and brown conidial colors were allelic and they segregated independently of mating type (13). Shoemaker (9) investigated sexuality in the fungus and found that pseudothecia developed from fertilized ascogonia, and protothecia developed from ascocarp initials. The protothecia and ground stroma of pseudothecia were of maternal origin only. Typically, in matings of compatible whiteand brown-spored strains both white and black pseudothecia were produced (13). Thus, in such pairings the direction of crossing was evident. The mating type to which a strain belongs is determined by pairing an unknown with tester strains. Generally white tester strains are used for dark-spored isolates and vice versa.