Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: RESISTANCE OF GENEVA AND OTHER APPLE ROOTSTOCKS TO ERWINIA AMYLOVORA

Authors
item Norelli, John (jay)
item Holleran, H. - CORNELL UNIVERSITY
item Johnson, W. - SEMINIS SEED, CALIFORNIA
item Robinson, T. - CORNELL UNIVERSITY

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 31, 2002
Publication Date: January 1, 2003
Citation: NORELLI, J.L., HOLLERAN, H., JOHNSON, W., ROBINSON, T. RESISTANCE OF GENEVA AND OTHER APPLE ROOTSTOCKS TO ERWINIA AMYLOVORA. PLANT DISEASE. JANUARY 2003; VOL. 87, NO. 1; PGS 26-32.

Interpretive Summary: Fire blight of apple rootstocks has become a serious economic problem in high-density orchard systems. The objective of the Geneva apple rootstock- breeding program has been to develop pomologically excellent rootstocks with resistance to abiotic and biotic stresses, including fire blight. Geneva (G.) 65, G.11, G.30, and G.16 were recently released for commercial sales, and several other selections are in the final stages of evaluation. Although the Geneva rootstocks are known to be resistant to direct shoot inoculation with E. amylovora strains Ea273 or E4001a, it was not known if these apple rootstocks are resistant to infection by E. amylovora through other avenues under orchard conditions or if they would be resistant to other highly aggressive strains of E. amylovora. Here we demonstrate that G.11, G.30, G.16, G.65 and most CG selections were resistant to four strains of E. amylovora in a non-differential manner. Field-grown fruiting 'Royal Gala' trees on G.16 and G.30 rootstocks were highly resistant to rootstock infection (no tree mortality) when trees sustained severe blossom infection with E. amylovora, in comparison with M.9 and M.26 rootstock clones, which were highly susceptible to infection (36 to 100% tree mortality). Orchard trees on G.11 were moderately resistant to rootstock infection (25% tree mortality). In contrast to potted own-rooted Bud.9 plants inoculated in a greenhouse, Bud.9 rootstocks of orchard trees appeared resistant to rootstock infection (0% tree mortality). New apple rootstocks that combined desirable pomological characteristics with resistance to infection by E. amylovora have the potential of providing practical control for the rootstock phase of fire blight in the future.

Technical Abstract: Budagovsky 9, Ottawa 3, M.9 and M.26 were the most fire blight susceptible rootstocks when vigorously growing shoots of 49 different apple rootstocks were inoculated in a greenhouse with different strains of Erwinia amylovora, and Geneva (G.) 11, G.65, G.16, G.30, Pi Au51-11, M.7 and several breeding selections were the most resistant. Significant strain by yrootstock interactions were observed in the amount of fire blight that resulted from inoculation. Field-grown fruiting 'Royal Gala' trees on G.16 and G.30 rootstocks were highly resistant to rootstock infection (no tree mortality) when trees sustained severe blossom infection with E. amylovora, in comparison with M.9 and M.26 rootstock clones, which were highly susceptible to infection (36 to 100% tree mortality). In contrast to potted own-rooted Bud.9 plants inoculated in a greenhouse, Bud.9 rootstocks of orchard trees appeared resistant to rootstock infection (0% tree mortality). Orchard trees on G.11 were only moderately resistant to rootstock infection (25% tree mortality).

Last Modified: 9/1/2014
Footer Content Back to Top of Page