CORRELATION IN THE TOLERANCE TO OZONE BETWEEN SPOROPHYTES AND MALE GAMETOPHYTES OF SEVERAL FRUIT AND NUT TREE SPECIES (ROSACEAE)

We analyzed relative sensitivities to ozone partial pressure for male gametophytes (pollen and pollen tubes) of five tree-crop species in th e family Rosaceae (almond, apple, apricot, nectarine/peach, pear) and of four cultivars of almond. Relative sensitivities to ozone partial p ressure were previously described using field-based, whole-plant, phys iological measurements for the sporophytes of each of the species and cultivars used in this study. Our objective was to determine the exten t of correlation between sporophyte and gametophyte responses to ozone among and within these tree species. If the relative sensitivities pr ove to be similar for the two generations, two research strategies bec ome possible for breeders interested in developing new cultivars with improved tolerance to atmospheric ozone: First, because screening larg e numbers of sporophytes for their responses to ozone partial pressure is a formidable task, exploiting the much more easily manipulated mal e gametophyte generation for large-scale screening of individuals for ozone tolerance could greatly facilitate identification and selection of tolerant genotypes. Second, it opens the possibility of applying se lection pressure to the gametophyte generation (as during pollen germi nation or pollen tube growth) to favor production of ozone-tolerant pr ogeny. Results indicate that, among and within species, relative respo nses of pollen tube growth to ozone partial pressure are highly correl ated with that of the sporophytes. Pollen germination was inhibited by ozone treatments for all but one species (pear), but differences amon g and within species were neither significant nor (with the exception of pear) did they correlate with relative sporophyte sensitivities.