The other way is using Reverse Genetic. Apply random insertion to knock-out the essential gene for sorghum height. Then go and find the dwarf phenotype. Once you have the plant, sequence the adjacent region of the insertion element to find out the locus.
"The authors found that loss of a gene product called a p-glycoprotein generates these dwarf corn and sorghum plants by interfering with the movement of auxin, an essential hormone in plant growth and development." (This paper was published in Science).