High-density genetic maps for loci involved in nuclear male sterility (NMS1) and sporophytic self-incompatibility (S-locus) in chicory (Cichorium intybus L., Asteraceae)

Abstract

High-density genetic maps were constructed for loci involved in nuclear male sterility (NMS1-locus) and sporophytic self-incompatibility (S-locus) in chicory (Cichorium intybus L.). The mapping population consisted of 389 F1' individuals derived from a cross between two plants, K28 (male-sterile) and K59 (pollen-fertile), both heterozygous at the S-locus. This F1' mapping population segregated for both male sterility (MS) and strong self-incompatibility (SI) phenotypes. Phenotyping F1' individuals for MS allowed us to map the NMS1-locus to linkage group (LG) 5, while controlled diallel and factorial crosses to identify compatible/incompatible phenotypes mapped the S-locus to LG2. To increase the density of markers around these loci, bulked segregant analysis was used. Bulks and parental plants K28 and K59 were screened using amplified fragment length polymorphism (AFLP) analysis, with a complete set of 256 primer combinations of EcoRI-ANN and MseI-CNN. A total of 31,000 fragments were generated, of which 2,350 showed polymorphism between K59 and K28. Thirteen AFLP markers were identified close to the NMS1-locus and six in the vicinity of the S-locus. From these AFLP markers, eight were transformed into sequence-characterized amplified region (SCAR) markers and of these five showed co-dominant polymorphism. The chromosomal regions containing the NMS1-locus and the S-locus were each confined to a region of 0.8 cM. In addition, we mapped genes encoding proteins similar to S-receptor kinase, the female determinant of sporophytic SI in the Brasicaceae, and also markers in the vicinity of the putative S-locus of sunflower, but none of these genes or markers mapped close to the chicory S-locus.

Current Advances in Genomics and Breeding of Leaf Chicory (Cichorium intybus L.)

“…Thus, independently of the intervention of external agents, self-pollination is possible in addition to open-pollination. In general, C. intybus is characterized by a strong sporophytic incompatibility system that usually inhibits self-fertilization and hence favorites cross-fertilization [2,10,[24][25][26][27][28]. Flowering occurs in the early part of the morning, mainly between 7:00 and 10:00 a.m., according to the air temperature and humidity.…”

“…In most cases, this is directly related to the manifestation of inbreeding depression and heterotic vigor as result of selfing and outcrossing, respectively [28,35,36].…”

“…High-density genetic maps including the loci responsible for sporophytic self-incompatibility (S-locus) and involved in nuclear male sterility (NMS-1 locus) have been published [28]. This study was performed using a mapping population of 389 F 1 individuals obtained by crossing two plants, one male-sterile and one male-fertile, both heterozygous at the S-locus, according to a method described by Eenink [24] and Varotto et al [25].…”

“…Thirteen and six AFLP markers were found genetically linked to the NMS1 locus and the S-locus, respectively. Eight of these markers were converted into locus-specific Sequence Characterized Amplified Region (SCAR) diagnostic assays, among which five exhibited co-dominant polymorphisms [28].…”

“…In addition, Gonthier et al [28] mapped genes encoding proteins similar to S-receptor kinase, the female determinant of sporophytic SI in Brassicaceae, and markers related to the putative S-locus of sunflower, family of Compositae, but none of these genes or markers mapped close to the chicory S-locus. Concerning male-sterility, neither candidate genes nor diagnostic markers are available for Cichorium spp.…”