Mycorrhizal Colonization of Grapevine Rootstocks under Field Conditions
2003
Schreiner, R Paul
Mycorrhizal colonization of grafted grapevines was studied during early establishment of an experimental rootstock vineyard to determine rootstock variability forming functional mycorrhizas. Roots of 10 different rootstocks were examined for the presence of arbuscular mycorrhizal (AM) fungi at the end of the second growing season (1998), and at the time of veraison (onset of ripening) of the third (1999) and fourth (2000) growing seasons. The fine root length density (primary roots with intact cortex) increased in 6 of 10 rootstocks over time. Only one rootstock, Riparia Gloire, showed a marked decrease in fine root length density in 2000, when vines carried their first significant fruit crop. AM colonization was generally above 60% of fine root length for all rootstocks, although significant differences due to rootstock and time of sampling were evident. Rootstocks imparting greater vigor to the scion, particularly Ruggeri 140, Kober 5BB, and SO-4, had consistently higher levels of root colonization by AM fungi. The proportion of roots containing arbuscules at veraison declined from 1999 to 2000 in those rootstocks carrying the highest crop loads. While AM colonization of different rootstocks was positively correlated to yield, the proportion of roots with arbuscules was negatively correlated to yield in 2000. Results of this study show that small differences in the ability to form mycorrhizas exist among rootstocks, but other factors, including crop load and soil moisture, have a large influence on root colonization by AM fungi.
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