PCR-based method for identifying the S-genotypes of Japanese pear cultivars

 Japanese pear (Pyrus pyrifolia Nakai), a member of the Rosaceae, shows gametophytic self-incompatibility that is controlled by the S-locus. The S-genotype of Japanese pear cultivars is an important factor for crossing and breeding. We report a rapid reliable method to identify these S-genotypes. It consists of PCR amplification of the S-RNase gene from genomic DNA and subsequent digestion of the PCR fragments with S-allele-specific restriction endonucleases. Using this method, we determined the unknown S-genotypes of nine Japanese pear cultivars and selected self-compatible varieties from the offspring of the self-compatible cultivar, ‘Osa-Nijisseiki’. Received: 8 June 1998 / Accepted: 19 October 1998     

Sequence of an S-protein of Lycopersicon peruvianum and comparison with other solanaceous S-proteins

Summary cDNA clones for an S-allele, designated S₅, of the self-incompatibility locus (S-locus) of Lycopersicon peruvianum have been isolated by probing a pistil cDNA library with cDNAs for S-alleles of Petunia inflata and Solanum chacoense. The longest S₅-cDNA is 869 bp and contains an open reading frame of 217 amino acids. An alignment of the deduced amino acid sequence of S₅-protein with that of the 18 S-proteins from five other solanaceous species is presented. Sequence comparison further refines the primary structural features of the S-proteins previously revealed from comparison of subsets of these sequences. Based on this comparison and evidence presented elsewhere, it is proposed that accumulation of point mutations, and not intragenic recombination, is responsible for the generation of new allelic specificities.     

Self-incompatibility RNases from three plant families: homology or convergence?

In the Rosaceae, Scrophulariaceae, and Solanaceae, the stylar product of the self-incompatibility (S-) locus is an RNase. Using protein sequence data from 34 RNase genes (three fungal RNases, seven angiosperm non-S RNases, 11 Rosaceae S-alleles, three Scrophulariaceae S-alleles, and ten Solanaceae S-alleles) we reconstructed the genealogy of angiosperm RNases using the neighbor joining method and two distance metrics in order to assess whether use of S-RNases in these families is the result of homology or convergence. Four monophyletic groups of angiosperm RNases were found: the S-RNases of each of the three families and a group comprising most of the angiosperm non-S RNases. The S-RNases of the Scrophulariaceae and Solanaceae were found to be homologous but strong inference concerning the homology or convergence of S-RNases from the Rosaceae with those of the other families was not possible because of uncertain placement of both the root and two of the angiosperm non-S RNases. The most recent common ancestor of the Rosaceae and both the Scrophulariaceae and Solanaceae is shared by ~80% of dicot families. If the -RNases of the Rosaceae are homologous to those of the Scrophulariaceae and Solanaceae, then many other dicot families might be expected to share RNases as the mechanism of gametophytic self-incompatibility.     

Genetic analysis of incompatibility in the diploid Ipomoea species closely related to the sweet potato

Summary In order to identify the genotypic constitutions of incompatibility in the diploid species, Ipomoea leucantha Jacq. (K221), which is most closely related to the sweet potato, the progenies derived from the reciprocal crosses, backcrosses and testcrosses were analysed. All the plants examined were self-incompatible, and pollen germination was inhibited on the stigma after incompatible pollinations. No reciprocal differences were found in the incompatibility reactions. In the progenies three incompatibility groups were observed which showed the rather simple segregation ratios. The homozygous plants for incompatibility alleles were obtained in the progenies. The experimental results demonstrated a sporophytic type of incompatibility controlled by a single locus with multiple S-alleles exhibiting a dominance relationship in both the pollen and the stigma. The plants obtained in the progenies had the following genotypes: S ₁ S ₂, S ₁ S ₃, S ₂ S ₂, S ₂ S ₃ and S ₃ S ₃.     

Self-compatibility in doubled haploids and their F1 hybrids,regenerated via anther culture in self-incompatible Solanum chacoense Bitt.

Summary Homozygous diploid plants originating from pollen of self-incompatible Solanum chacoense clone IP33 were analysed genetically. Among the tested individuals, two were self-compatible. As expected, all the regenerants were compatible, as pistillate parent, with the mother clone. However, three plants also displayed compatibility in the reciprocal crosses. Abnormal S-gene behaviour was observed when some androgenetic plants were intercrossed. In addition in the F₁ hybrids between doubled haploids, the S-gene did not appear to function as expected, suggesting that some changes, possibly the generation of new S-alleles, had occurred.     

Dominance relationships among S-alleles in Corylus avellana L.

Summary Pollen-stigma compatibility relationship were studied in 50 cultivars and more than 800 seedlings of the European hazelnut (Corylus avellana L.). A total of 22 unique S-alleles have been identified. Dominance relationships in 75 of the possible 231 pairs of alleles have been determined in both pistil and pollen. In the pistil, all alleles exhibited independent action, whereas in the pollen, alleles exhibited either dominance or codominance. The dominance relationship was linear with 7 levels of dominance.Oregon Agricultural Experiment Station Technical Paper No. 8542     

Revised dominance hierarchy for S-alleles in Corylus avellana L.

Pollen-stigma compatibility was studied in cultivars and more than 1800 seedlings of the European hazelnut (Corylus avellana L). Four new S-alleles were identified, bringing the total to 25 unique alleles within C. avellana. The new alleles are the recessive alleles in ‘Tonda di Giffoni’ and ‘Segorbe’ (S₂₃), in ‘Neue Riesennuss’ (S₂₅), in ‘Gasaway’ (S₂₆), and a dominant allele in a seedling of Turkish origin (S₂₄). Dominance relationships in 233 of the possible 300 pairs of alleles were determined in both pistil and pollen. All alleles exhibited independent action in the pistil, whereas in the pollen either dominance or codominance was exhibited. The dominance hierarchy of alleles in the pollen was revised in light of the new information obtained. All 25 alleles have been assigned to a level in the hierarchy that is linear and now has eight levels. S₆ and S₉ were reassigned to lower levels in the hierarchy. Thirteen of the alleles are on the level of S₁, while S₄, S₆, S₁₁, and S₂₃ occupy unique positions in the hierarchy. Improved pollen tester clones were identified for several S-alleles. The alleles in 55 cultivars were determined. The alleles identified in ‘DuChilly’ (S₁₀ S₁₄) did not agree with previous reports. Four cultivars have the same alleles as ‘Römische Nuss’ (S₁₀ S₁₈) and are morphologically indistinguishable from it: ‘Frutto-grosso’, ‘Istarski Okrogloplodna’, ‘Payrone’, and ‘Romai’. ‘Belle di Giubilino’ and ‘Tonda di Biglini’ are both S₁ S₁₀ and appear to be synonyms for the same cultivar.     

Incompatibility in angiosperms

 Since Darwinian times considerable knowledge has accumulated on the distribution, physiology and genetics of self-incompatibility (SI) in higher plants. In the second half of this century the first attempts were made to identify the biochemical bases of SI. These included thediscovery that cutinase enables pollen tube penetration at the surface* of the stigma in Cruciferae, sorting of segregation pollen S-phenotypes by serological techniques, a lock-and-key model of the SI reaction, the first detection and characterisation of SI proteins and the discovery of the role of the tapetum in the determination of pollen phenotypes in homomorphic sporophytic SI. This pioneering work was followed by a worldwide effort to identify and understand the cellular and molecular processes which lead to the recognition and rejection of SI pollen. The present review article summarizes briefly the current state of knowledge in areas essential for the understanding and exploitation of SI and outlines new information that has become available during recent years. Received: 14 March 1997 / Revision accepted: 10 June 1997     

利用S位点多态性快速测定甘蓝自交不亲和性及其S等位基因系

Specific primers were designed according to the sequences of class Ⅰ and class Ⅱ SLG genes. The PCR products using these primers amplified from the cabbage　(Brassica oleracea L.) gDNAs of Southwest China Agricultural University (SCAU) and Horticulture Research International (HRI), Wellesbourne, showed that those with class Ⅰ SLG genes were strong self-incompatibility (SI) lines and those with class Ⅱ were included both strong and weak SI lines. Thus the whole length of DNA fragment of class Ⅱ SLG gene may be the molecular marker for distinguishing SI lines from SC lines. Furthermore, RFLP analysis of the class 　Ⅱ SLG genes from various S-alleles of cabbage was conducted by using 6 restriction endonucleases which recognize 4 bp DNA sequence and the results showed that the S-alleles from HRI as well as the weak SI lines from SCAU presented obvious different RFLP profiles which could be used for distinguishing S-alleles of cabbage.