No abstract

Protein stylar extracts of 16 cultivars of sweet cherry (Prunus avium), from the 10 different incompatibility groups to which incompatibility alleles have been assigned, were separated on acrylamide gels using isoelectric focusing (IEF) and were stained for ribonuclease activity. When two cultivars from the same incompatibility group were analyzed they gave identical zymograms and the cultivars of the 10 different incompatibility groups gave in all eight distinct zymograms. The ribonuclease polymorphism could be correlated with the reported S allele constitutions of the cultivars. Three ribonuclease bands were identified that each consistently corresponded to one of the six known incompatibility alleles (Sl , Ss and S,), a fourth band apparently corresponded to Ss and to the combination of S, and Ss, and a fifth band to S, and S5 in other combinations. Thus, it seems that S alleles of cherry have ribonuclease activity and that IEF is useful for distinguishing S allele constitutions. The ribonuclease pattern of 'Summit', a cultivar of unknown incompatibility group, indicated its incompatibility genotype to be S1 Ss , and this was confirmed by controlled pollination. The same band corresponded to S, and Sq ', the mutant allele in self-compatible cultivars. IEF and ribonuclease staining promise to be useful tools for exploring the incompatibility relationships of cherry cultivars and perhaps of other self-incompatible Prunus crops.

The work aimed to develop a reliable and convenient PCR approach for determining incompatibility S genotypes in almond. Initially, genomic DNAs of 24 accessions of known S genotype were amplified with novel consensus primers flanking the first and second introns of the S-RNase gene. The PCR products separated on agarose showed length polymorphisms and correlated well with the reference alleles S 1 -S 23 and S f . In addition, to improve discrimination between alleles of similar sizes, the same sets of primers but fluorescently labelled were used, and the products sized on an automated sequencer. These fluorescent primers were particularly informative in the case of the first intron, variation in the length of which has not been used previously for S genotyping in almond. Some reference alleles showed the same patterns with first and second intron primers, and others showed a microsatellite-like trace. Subsequently, the S genotypes of 26 cultivars not genotyped previously and of four of uncertain genotype were determined. An allele described in Australian work as putative S 10 was shown to be a ÔnewÕ allele and ascribed to S 24 and evidence of five more ÔnewÕ S alleles was found, for which the labels S 25 -S 29 are proposed. This PCR approach should be useful for genotyping in other Prunus crops.Most cultivars of almond [Prunus dulcis (Mill.) D.A. Webb] are self-incompatible and some are cross-incompatible (Tufts and Philp 1922). The incompatibility system is of the gametophytic type and controlled by a multi-allelic S locus (Gagnard 1954). To obtain good yields at least two cross-compatible cultivars of coincident flowering time should be planted together.Initial studies conducted to determine incompatibility genotypes in almond cultivars used controlled crosses. CrossaRaynaud and Grasselly (1985) proposed the existence of six different self-incompatibility alleles (S 1 , S 2 , S 3 , S 4 , S 7 and S 8 ) and the self-compatible allele S f in various European cultivars. Later, Kester et al. (1994) assigned four S alleles (S a , S b , S c and S d ) to explain the incompatibility groups of some American cultivars studied.Finding that almond incompatibility S alleles code for stylar proteins with ribonuclease activity that can be separated electrophoretically by isoelectric focusing (IEF) and non-equilibrium pH gradient electrofocusing (NEPHGE), Bosˇkovic´et al. (1997) determined the S genotype of 29 almond cultivars. This study corroborated the results obtained previously by Crossa-Raynaud andGrasselly (1985) andKester et al. (1994), and identified S 1 with S b , numbered S a as S 5 , and proposed two more alleles, S 6 and S 9 . In subsequent studies, the alleles S 10 (Bosˇkovic´et al. 1999), and S 11 and S 12 (Bosˇkovic´et al. 1998) were indicated and two more cultivars genotyped. Recently, 35 more cultivars (mostly of American origin) were genotyped with the same techniques and the alleles S 13

No abstract