Suitability of four different methods to identify self-compatible seedlings in an almond breeding programme

Abstract

SummaryObtaining self-compatible almond cultivars from controlled crosses has become one of the most important aims in almond breeding programmes. Self-compatible seedlings from such crosses have been identified by different methods. Determination of fruit set in bagged branches and observing self-pollen growth along the pistil by fluorescence microscopy are methods traditionally used. Non-equilibrium pH gradient electro-focusing (NEPHGE) of stylar S-RNases is a more recent method, which reveals self-compatibility by partial or total absence of ribonuclease activity in heterozygous and homozygous self-compatible individuals respectively. To date, the most recent method is S-allele PCR, which identifies the presence of the Sf allele in genomic DNA. In this work, reliability, ease of performance, economic cost and time spent in obtaining the results of these four methods were compared in a progeny of 74 seedlings. The results showed that, considering its moderate cost and time spent, NEPHGE of stylar S-RNases was the most convenient method. However, as PCR of S-alleles can be applied in the first year to plantlets in the nursery, an early selection of self-compatible seedlings is possible. On the other hand, bagging is essential in a further stage of the selection process, thus ensuring good yields in single-cultivar almond orchards.