<i>S</i> haplotype collection in Brassicaceae crops—an updated list of <i>S</i> haplotypes

Abstract

Self-incompatibility is the system that inhibits pollen germination and pollen tube growth by self-pollen. This trait is important for the breeding of Brassica and Raphanus species. In these species, self-incompatibility is governed by the S locus, which contains three linked genes (a set called the S haplotype), i.e., S-locus receptor kinase, S-locus cysteine-rich protein/S-locus protein 11, and S-locus glycoprotein. A large number of S haplotypes have been identified in Brassica oleracea, B. rapa, and Raphanus sativus to date, and the nucleotide sequences of their many alleles have also been registered. In this state, it is important to avoid confusion between S haplotypes, i.e., an identical S haplotype with different names and a different S haplotype with an identical S haplotype number. To mitigate this issue, we herein constructed a list of S haplotypes that are easily accessible to the latest nucleotide sequences of S-haplotype genes, together with revisions to and an update of S haplotype information. Furthermore, the histories of the S-haplotype collection in the three species are reviewed, the importance of the collection of S haplotypes as a genetic resource is discussed, and the management of information on S haplotypes is proposed.

Development of self-compatible Chinese cabbage lines of Chiifu through marker-assisted selection

“…The B. rapa reference genome line Chiifu, characterized by a CI value < 1.0 at the anthesis stage, served as the receptor parent. Its S -haplotype is S 60 (class II), as detailed in a recent study ( Yamamoto et al., 2023 ). A Yellow Sarson line, R-o-18, exhibiting a CI value > 10, was employed as the donor parent.…”

“…The self-incompatibility (SI) in Chinese cabbage is regulated by a multi-allelic S locus, encompassing three genes associated with pollen-pistil recognition: SRK ( S-locus receptor kinase ), SCR/SP11 ( S-locus cysteine-rich protein/S-locus protein 11 ), and SLG ( S-locus glycoprotein ) ( Yamamoto et al., 2023 ). The genetic set of alleles of these genes at the same S locus is designated as the ‘ S haplotype’ ( Nasrallah and Nasrallah, 1993 ).…”

“…Two distinct forms of MLPK , MLPK form 1 ( MLPKf1 ) and MLPK form 2 ( MLPKf2 ), localize to the papilla cell membrane and directly interact with SRK to transduce SI signaling ( Kakita et al., 2007 ). The Chiifu accession carries the S 60 haplotype on chromosome A07 ( Yamamoto et al., 2023 ), characterized by MLPK -dependent self-incompatibility ( Ohata et al., 2023 ). However, the practical challenge of breeding self-compatible Chinese cabbage lines based on MLPK remains unresolved.…”

Self-incompatibility phenotypes of SRK mutants can be predicted with high accuracy

“…Population genetic theory predicts that many S haplotypes should be maintained, given that individuals possessing rare S haplotypes have more mating opportunities than those carrying common haplotypes (Wright, 1939, Schierup 1998. Consistent with this, more than 50 S haplotypes, each of which shows different self-recognition activity, are known from cultivated Brassica species (Oikawa et al 2011, Yamamoto et al 2023. SI in the Brassicaceae is genetically controlled by two tightly linked, highly polymorphic genes within the S locus.…”