Vol. 83 No: 5

Title:
Identification of S-genotypes and novel S-RNases in native Chinese pear

Authors:
W. HENG, H.Q. WU, S.X. HUANG, S.J. ZHANG, J. WU, C.Q. FANG and S.L. ZHANG

pp: 629-634

Abstract:
Chinese pear (Pyrus spp.) exhibits gametophytic self-incompatibility (GSI), as do other fruit species in the family Rosaceae. This work determined S-locus diversity in 20 native Chinese pear cultivars or wild accessions using polymerase chain reaction (PCR) and pollination experiments. After cloning and sequencing the PCR products, the S-genotypes of all 20 pear cultivars or wild accessions were determined. Subsequent sequence analysis showed that P. sinkiangensis Yű ‘Aolian’ (S_pS₃₂), P. phaeocarpa Rehd. ‘Diaodan’ (S_dS_e), and P. xerophila Yű ‘Shageda’ (S₃₆S_d) and ‘Xingyeli’ (S₂₂S_c), originating in China, shared some S-RNase genes with P. communis, providing evidence that oriental and occidental Pyrus species may share the same pool of alleles at the S-locus. Two novel S-RNase genes were also discovered in P. ussuriensis ‘Maili’ and ‘Neimenggushanli’, and deposited as S₄₀ and S₄₁, under the accession numbers DQ903313 and DQ988687, respectively. Their deduced amino acid sequences showed high similarity to S₁₁-RNase (100% ) and S₆-RNase (94.4%) between the C1 and C3 exons in Malus. The high similarity scores between S-RNases in Pyrus and Malus indicate that the existence of S-RNases predated speciation between Pyrus and Malus.

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