A Phenotypic Search on Graft Compatibility in Grapevine

Abstract

Grafting is the most used propagation method in viticulture and is the unique control strategy against Phylloxera. Nevertheless, its practice remains limited mainly due to inconsistent graft success and difficulties in predicting graft compatibility responses of proposed scion–rootstock combinations, slowing down the selection of elite rootstocks. Aiming to identify optimal phenotypic parameters related to graft (in)compatibility, we used four clones of two grapevine cultivars that show different compatibility behavior when grafted onto the same rootstock. Several physiological parameters, internal anatomy of the graft union, chlorophyll fluorescence, and pigment contents of homo- and heterografts were monitored in a nursery-grafting context. The measurements highlighted enhanced performance of the heterografts due to rooting difficulties of Vitis vinifera homografts. This suggests that in viticulture, homografts should only be used as compatibility controls regarding qualitative attributes. By observing the internal anatomy of the union, we found that grapevines might require longer times for graft healing than anticipated. While Affinity Coefficients were not informative to assess incompatibility, leaf chlorophyll concentration analysis proved to be a more sensitive indicator of stress than the analysis of chlorophyll fluorescence. Overall, we conclude that graft take correlated best with callus formation at the graft junction three weeks after grafting.

Differential transcription pathways associated with rootstock-induced dwarfing in breadfruit (Artocarpus altilis) scions

“…As the performance of a grafted plant and the commercial application of the rootstock not only depends on the genotype of scion and rootstock, but also the compatibility of the rootstock with scion [ 16 – 18 ], it is necessary to examine the graft combination of breadfruit/marang for graft compatibility. Anatomy examination of a scion/rootstock union has been a method that unambiguously identifies graft incompatibility in woody species [ 19 – 21 ]. Anatomy examination of graft interface was first carried out on the graft unions of three interspecific grafts at 26 months after grafting.…”

“…The results revealed that the breadfruit/marang grafts had good compatibility with hardly visible graft lines in bark and wood (category ‘A’, see Methods, also [ 22 ]) and there was no discontinuities along the graft lines between bark and wood in all the graft unions examined (see example image in Figure S 2 ). The ratio of the stem diameter above and below the graft union has often been used to correlate growth characteristics with graft incompatibility [ 19 – 21 ]. In consistent with the anatomy assessment, the ratio of scion to rootstock stem diameter in the breadfruit/marang combination was very close to 1, and there was no significant difference between those of the self-graft and the interspecific graft (Table S 1 ).…”

“…In consistent with the anatomy assessment, the ratio of scion to rootstock stem diameter in the breadfruit/marang combination was very close to 1, and there was no significant difference between those of the self-graft and the interspecific graft (Table S 1 ). Scion leaf chlorophyll (Chl) concentration, reflecting the capability of carbon assimilation and proper functioning of a composite grafted plant, has also served as a non-destructive tool to identify graft incompatibility [ 19 – 21 ]. Here, concentration of scion leaf chlorophyll on marang rootstocks, including Chl a , Chl b , Chl a + Chl b , and Chl a/b was not significantly different from those of the self-graft (Table S 1 ).…”

Mechanisms Underlying Graft Union Formation and Rootstock Scion Interaction in Horticultural Plants

“…In grapevine it was found that it is not the graft take rates but the status of callus formation at 21 DAG which is an indicative of compatibility between the stock and scion. Moreover, analysis of leaf chlorophyll content can also serve as an efficient means to estimate the compatibility ( Tedesco et al, 2020 ). The difference in the quality and quantity of phenol in the stock and scion can point toward metabolic dysfunctions at the graft union ( Errea, 1998 ) and can serve as a biochemical marker to predict graft incompatibility ( Musacchi et al, 2000 ).…”

Identifying Molecular Markers of Successful Graft Union Formation and Compatibility

“…The causes of graft incompatibility are multiple; genetic proximity, poor craftsmanship, climatic conditions or pathogens can harm a successful graft union formation and maintenance as well as differences in the metabolism of the scion and the rootstock. It is difficult to know if a grafted plant will survive or die, moreover, there are few visual indicators of grafting success at an early stage of development ( Figure 1B ) (Tedesco et al, 2020 ). The identification of molecular markers of grafting success would be a great advantage for genetic research and rootstock selection programs.…”