OUINBV: MUTATIONS IN SORGHUMS 195 



as periconia root rot (18) and caused by the fungus Periconia cir- 

 cinata. This disease suddenly became widespread during the drought 

 years beginning in 1934. A number of varieties of milo parentage, 

 including Day, Colby, Wheatland, and Beaver, were also suscep- 

 tible as was Darso and one strain of Sumac, a somo variety. Resistant 

 plants in Dwarf Yellow milo were quickly found in Kansas (44) and 

 in Texas (27). Bowman, et al. (4) reported susceptibility as being 

 partially dominant and controlled by a single major gene. In Texas 

 (27), resistant plants were invariably found to be homozygous resist- 

 ant. Resistant plants that occurred occasionally in susceptible 

 strains must have occurred due to mutation. In pure milo, resist- 

 ant selections were found in one strain in Kansas, two in Texas, 

 and three in California (31). Resistant plants of Beaver were found 

 at both Dalhart, Texas, and Garden City, Kansas. Resistant plants 

 of Day and Colby were found in Kansas. Resistant Darso selections 

 were found at Temple and Chillicothe, Texas, and at Stillwater, 

 Oklahoma. Resistant plants of exact Wheatland type were never 

 found in diseased fields of Wheatland, but resistant plants found 

 in such fields were distributed as Martin, Resistant Wheatland No. 

 288, and Dalhart Resistant Wheatland. 



Yield trials over long periods of years at the Texas Substations 

 at Chillicothe and Lubbock (27) have shown that losses of 50 to 

 60 per cent can be expected whenever a susceptible variety is grown 

 on infested soil. Fortunately, all varieties grown to any extent and 

 most parents of hybrids now in production are resistant to periconia 

 root rot. 



The three smuts of sorghum in the United States are covered 

 kernel smut, Sphacelotheca sorghi, loose kernel smut, S. cruenta, and 

 head smut, 5. reiliana. Both kernel smuts can be controlled with chem- 

 ical seed treatments, but head smut is soil-borne. Resistance to the 

 four races of covered kernel smut is present in Spur Feterita. Casady 

 (5) has recently reported on the inheritance of resistance to S. sorghi. 



Head smut has recently become a problem in Texas, probably 

 because of the widespread planting of a susceptible variety, Com- 

 bine 7078, and several susceptible hybrids. The inheritance of 

 resistance has not yet been determined, but heritable resistance 

 exists since selections from resistant strains in a nursery in Refurio 

 County on the Texas Gulf Coast in 1959 were resistant again in 



