QUINBV: MUTATIONS IN SORGHUMS 191 



in Blackhull Kafir that farmers were growing by 1900. Recessive 

 c/u'i was found before 1905 and recessive dw 2 about 1910, both in 

 milo. The combine height varieties that originated in the 1920's 

 and later were recessive for three height genes were obtained by 

 selecting 3-dwarf segregates from crosses between milo (dw x Dzv 2 

 Dw 3 div 4 ) and kafir (Dzu 1 Dw 2 dw 3 dzv 4 ). The dominant gene in all 

 of the 3-dwarf varieties of milo-kafir parentage is Dw 2 and in the 

 3-dwarf milos Diu s . Four-dwarf strains have been obtained by cross- 

 ing these two 3-dwarf genotypes (dw x Diu 2 dw s dw± and dw x dw 2 

 Dius duu) and selecting 4-dwarf segregates. The genetic height 

 constitution of many varieties and parents of sorghum hybrids 

 and broomcorn is known. The genetic identity of many strains is 

 given in Table 4. At Chillicothe, Texas, on dryland 2-dwarfs were 



Table 4. — Classification of Sorghum Varieties According to Height. 



Genotype Variety 



Dw\ Dw> Dw-i Dw\ None identified 



Dwi Dwi Dw-i dwi Tall White Sooner Milo SA 1170, Spur Feterita, Manchu Brown 



Kaoliang, Shallu SA 401, Sumac 

 Dit'i Dw<i dw 3 Dw\ Standard Broomcorn 

 Dw\ dwz Du>3 Dwt None identified 

 dwi Dw-2 Dws Du'i None identified 

 Dwi Dw : dwi dwi Texas Blackhull Kafir, Kalo, Early Kalo, Chiltex, Shantung Dwarf 



Kaoliang 

 Dw\ dw-i Dws dw\ Bonita, Early Hegari, Hcgari 

 dw i Dw-i Dw-i dwt Dwarf Yellow and White Milos, Sooner Milo 

 Dw i dw-i dws Dw\ Acme Broomcorn 

 dw\ Dwt dwz Dixn Japanese Dwarf Broomcorn 

 dw\ dw^ Dwz Dwa None identified 

 Dw\ dw-i dwz du>i None identified 



dw\ Dw-i dw 3 dwi Combine Kafir 60, Combine 7078, Martin, Plainsman, Wheatland, 



Caprock, Combine White Feterita SA 396, the Redbines, Day 

 dw\ dwo Dwz dwi Double Dwarf Yellow Milo, Double Dwarf Yellow and White 



Sooner Milos, Ryer Milo 

 dw\ dwi dwz Dwi None identified 



dw\ du>2 dwz dw t SA 403, 4-dwarf Martin, 4-dwarf Kafir 



usually about 50 cm shorter than 1 -dwarfs; 3-dwarfs about 40 cm 

 shorter than 2-dwarfs; and 4-dwarfs about 10 cm shorter than 3- 

 dwarfs. As more recessive genes accumulate in a strain, the dwarfing 

 effect is obviously lessened. 



Two of four height genes are unstable. Mutations to tallness in 



