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False erosion of horizontal resistance to phylloxera in California vineyards. Considerations and outlook
L. Chiarappa and I.W. Buddenhagen
Vol. 33, No. 1 (April 1994), pp. 1-9
Stable URL: http://www.jstor.org/stable/42685912
Page Count: 9
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Major developments in breeding for durable genetic resistance to crop parasites are examined in relation to the devastating experiences with phylloxera in Europe and California. From these studies, which include an analysis of the ongoing phylloxera epidemic in Napa and Sonoma valleys, it is concluded that the resistance of 'Rupestris St. George' is still effective against all forms of the parasite, while that of the hybrid 'AxR#1' is no longer functioning. This strongly suggests that phylloxera resistance is horizontal in 'Rupestris St. George' (and other American rootstocks) and that this is operating at close to a maximum level. This is not the case for the susceptible 'AxR#1' rootstock. Some of the reasons and evidence for this conclusion are presented. The need for comprehensive horizontal resistance in grape rootstocks to all major soil parasites is emphasized.
Phytopathologia Mediterranea © 1994 Mediterranean Phytopathological Union