Intervarietal grafting, and in some cases interspecific grafting, practiced mainly in horticultural crops has many practical applications. Grafting can also be a useful tool to perform basic physiological, biochemical, and molecular studies to better understand communication between shoot and root in a row crop, such as cotton. We have established a grafting protocol for upland cotton (Gossypium hirsutum L.) genotypes. Although less efficient, it can be used to create grafts between upland and Pima (G. barbadense) or Old-world cottons (G. arboreum or G. herbaceum). The procedure used 8-day-old seedlings grown in culture under sterile conditions to obtain the scion and rootstock. The scion consisted of the shoot apical meristem with a few leaf primordia, epicotyl, and a small portion of the hypocotyl with the cotyledons removed. The rootstock retained 2 to 3 cm of basal hypocotyl portion with the roots trimmed. Cleft grafts were assembled under aseptic conditions followed by their culture in vitro. Once established, as indicated by the healthy growth of three to four true leaves and roots, the grafts were moved to soil in small pots. After hardening the grafts on a laboratory bench for few weeks, they were transferred to larger pots and grown to maturity in a greenhouse to obtain seeds. The success rate using our protocol ranged from 90 to 100% for Coker 312 genotype and its derivative transgenic and gene edited lines. The method was also applicable to generate intervarietal and interspecific graft unions among various types of cotton plants.
