Inheritance of Resistance to Phylloxera in Fland F2 Populations of Grape

Approximately 1,170 of the 1,540 seed from the controlled crosses to create population 1 were germinated from June until August. About 980 plants completed germinating and were planted in 2Vi” pots and then inoculated when they were one month old. They were evaluated in January, 2000 and only one plant was found infected with phylloxera. The poor results may have been due to the small seedling roots. The seedlings have been re-potted and inoculated again. For population 2, cuttings were taken from 950 plants in the field. Four leafy cuttings per plant were mist propagated for a total of 3,800 cuttings. All cuttings that rooted were transplanted to 2V4″ pots and inoculated with phylloxera eggs at that time. The first cuttings were taken June 21 and the last cuttings taken August 12, 1999. The rooted cuttings have much stronger roots than plants started from seed and it seems easier for the phylloxera to become established on them. Good phylloxera infection was obtained for the crosses 1 to 9 resulting in good evaluation of resistance and susceptibility. Poor results were obtained for crosses 15 to 20 because they were inoculated after the first of September. Plants were inoculated again after their evaluation to fully test their resistance and eliminate the possibility of escapes. The occurrence of phylloxera on the roots is positive identification of susceptible individuals. There was good correlation between the tests conducted in the 6″ pots and the 2Vi” pots. Susceptible parents generally produce susceptible offspring except when Kober 5BB was the resistant parent. Based on this progeny test, Kober 5BB has the highest level of resistance that is passed to its offspring. Because of the low number of individuals in certain crosses, they were repeated this spring. A total of 237 seed were produced from the four crosses made. They have been stratified and are ready for planting. Work on molecular markers was not started. The resistant/susceptible nature of the seedlings needs to be determined first.