ISHS Acta Horticulturae 591: III International Symposium on Pistachios and Almonds
MULTIPLE GENETIC FACTORS CONTROL SELF-FERTILITY IN ALMOND |
| Authors: | T.M. Gradziel, P. Martínez-Gómez, A. Dandekar, S. Uratsu, E. Ortega |
| Keywords: | Self-compatibility, Prunus dulcis, S-allele, flower structure, PCR markers. |
| Abstract:
Highly self-fruitful almonds have been developed which combine self-compatibility with autogamy (self-pollination). Pollen-pistil self-compatibility is known to be determined by a single genetic locus (S-locus). Specific SSC-alleles conferring self-compatibility, along with the major self-incompatibility alleles controlling cross-incompatibility in California cultivars, have been identified through DNA analysis, including DNA sequencing. S-alleles specific PCR analysis has been employed to select breeding combinations that ensure that all progeny inherit the allele conferring self-compatibility. Although the presence of the self-compatibility allele was confirmed in resulting progeny, self-fruitfulness following controlled pollinations varied widely, demonstrating the importance of proper genetic background for consistent expression of this trait. The level of autogamy also varied greatly among progeny, with floral structure and the timing of pollen-dehiscence appearing to be crucial factors. The high variability in the level of self-pollination supports a continued need for insect pollinators in order to maximize yields. Important factors determining the frequency of insect visitations include the quality and quantity of nectar and pollen, and floral cup and anther structure. The presence of pubescence at the floral nectaries, either at the hypanthium and/or the pistil base, appear to be important for nectar volatilization and so attractiveness to honeybee pollinators. With the exception of the S-locus, most factors controlling self-fertility appear to have complex inheritance. | |
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