Noninfectious bud failure in 'Carmel' almond. I. Pattern of development in vegetative progeny trees

The spatial and temporal pattern of noninfectious bud failure (BF) expression (BF(exp)) was studied during seven growing seasons in a population of 'Carmel' almond trees originating from twelve commercial propagation sources. All progeny trees were grown in a single experimental site with high prevailing summer temperatures. BF(exp) increased continuously but irregularly in each nursery population as measured as the proportion of trees showing BF and as an average BF(exp) rating. Populations from the 12 nurseries represented increasing clonal generations from the original seedling tree and showed increasing levels of BF, as well as a decreasing shape value and increasing scale value derived by a failure statistics model. Models for development, distribution and hazard functions were defined for each of the 12 sources studied. Only sources from the original tree and source A demonstrated potential for commercial use. A significant correlation was found between average yearly increase in BF(exp) and the average daytime temperature for the previous June. The June period coincides with a specific stage in the seasonal growth cycle when vegetative buds mature.