Histological Evaluation of Early Graft Compatibility in Uapaca kirkiana Müell Arg. Scion/Stock Combinations

Abstract

<jats:p>Compatibility of scion and stock combinations in <jats:italic>Uapaca kirkiana</jats:italic> fruit trees has not been evaluated despite noticeable growth irregularities. The objectives of this study were to determine graft compatibility of scion/stock combinations and possible causes of graft incompatibility. Scion, stock, and graft union diameters were measured. Stem sections comprising the graft unions were immersed in formalin acetic acid and then washed in sterile water. These were transversely dissected across the unions and examined under using light microscope. There were considerable growth disorders at the unions, which included significant overgrowth of stocks and unions and constricted unions. There were cracks in the bark across the union in many graft combinations. Anatomic and histological studies showed accumulation of phenol deposits and necrotic tissues, and there was no continuity of vascular tissues above the union. There were also differences in proliferation of callus tissues among grafted partners. Continuity in wood and bark tissues below the unions supported growth of partially compatible partners, whereas isolated parenchymatous tissues at the union supported growth of incompatible partners. There were many necrotic tissues and unfilled areas above the union. Accumulation of phenolic and necrotic cell deposits, poor or a high level of callusing at the union, and possibly specific incompatibility reactions were implicated as the causes of graft incompatibility in <jats:italic>U. kirkiana</jats:italic> trees.</jats:p>

Phenolic Compounds Involved in Grafting Incompatibility of Vitis spp: Development and Validation of an Analytical Method for their Quantification

“…In viticulture, after the devastating occurrence of root louse phylloxera that started in 1880, grafting became a widespread technique to overcome pathological or soil problems, where the scion is a cultivar of Vitis vinifera L. and the rootstock is either an American Vitis species or an interspecific hybrid. However, as in other fruit species, such as pear‐quince (Musacchi et al ., ), apricot (Errea et al ., ; Usenik et al ., ), loquat (Mng'omba and du Toit ; Mng'omba et al ., ) or pear (Ciobotari et al ., ), graft incompatibility is an unresolved worldwide problem, and the means to reduce losses caused by such a problem are strictly limited when a vineyard is already established.…”

Gene regulatory networks for compatible versus incompatible grafts identify a role for SlWOX4 during junction formation

“…Continuous xylem files span the graft junction in the self-grafted tomato and pepper plants, indicating that nutrient and water flow was restored between the scion and stock (Figure 1E, 1H). Our anatomical imaging showed that these new xylem strands were formed toward the periphery of the junction, creating a thickened xylem bridge (Figure 1E, 1H; Mng’omba et al, 2007). Conversely, the heterografts showed an overproliferation of disorganized metaxylem above and below the graft interface (Figure 1F-G, 1J-K).…”

Ethnoecological Knowledge for Identifying Elite Phenotypes of the Indigenous Fruit Tree,Uapaca kirkianain the Miombo Woodlands of Southern Africa

“…Reducing this long vegetative phase could speed up domestication and adoption into farmland (Mng'omba et al 2007;). This could be accomplished through vegetative propagation such as grafting and air layering.…”