Cracked Root Mutant in Cotton: Inheritance and Linkage with Fertility Restoration1

A cracked root condition was observed in a line of upland cotton (Gossypium hirsutum L.) with G. harkenssii Brandegee cytoplasm. F1, F2, and testcross generations were grown to determine the inheritance of the cracked root condition. Observations indicate the character to be controlled by a single gene pair expressing complete dominance in upland stocks. In F1 hybrids between homozygous dominant cracked root upland plants and normal root G. barbadense L. plants, roots appear to be normal to slightly cracked, and inheritance is uncertain. Data indicate linkage of cracked root and fertility restoration with observed recombination values ranging from 6.7 to 14.5%. The symbol Rc is proposed for the gene responsible for the cracked root phenotype and the symbol Rf is proposed for the fertility restoring gene.