Susumu Yui

Identification and mapping of a quantitative trait locus controlling extreme late bolting in Chinese cabbage (Brassica rapa L. ssp. pekinensis syn. campestris L.) using bulked segregant analysis

DNA markers linked to a locus controlling an extreme late bolting trait, which was originally found in a local cultivar of a non-heading leafy vegetable,‘Osaka Shirona Bansei’ (Brassica rapa L. ssp. pekinensis syn. campestris L.) were identified using bulked segregant analysis. A doubled haploid (DH) line, DH27, which is a progeny of ‘Osaka Shirona Bansei’, shows extreme late bolting, and bolts without vernalization. DH27 was crossed with a normal bolting DH line, G309. The plantlets of the parents, F1 and F2, were vernalized and then grown in a greenhouse. The bolting time of F2 plants showed a continuous distribution from 19 to 231 days after vernalization (DAV), suggesting the effects of a few major genes and polygenes. Possible linkage markers for this trait were screened by modified bulked segregant analysis (BSA). The BSA using four bulks suggested that a 530-bp RAPD band RA1255C was linked to a locus controlling the bolting trait. The RAPD band was cloned and used as a probe to detect RFLP. The fragment detected a single locus, BN007-1,the segregation of which in the F2 population matched that of RA1255C. Three other RAPDs were found to be linked to BN007-1. A quantitative trait locus(QTL) affecting the bolting time was detected around BN007-1 using MAPMAKER/QTL. Since the difference between bolting times of both the parental genotypes in the F2 was 138 days, these markers may be useful for a marker-assisted selection (MAS) in the breeding program for late bolting or bolting-resistant cultivars in B. rapa crops.

Bolting resistant breeding of Chinese cabbage. 1. Flower induction of late bolting variety without chilling treatment

SummaryWhen a local slow bolting variety ‘Osaka Shirona Bansei’ (Brassica rapa L. ssp. pekinensis, syn. B. campestris L. ssp. pekinensis) was grown in a phytotron (25°C, 16 hours day length without chilling treatment), one third of the plants bolted and flowered. In order to clarify the different flowering responses in the variety, a progeny line (FNC) of the flowering plants was chilled for 4 different periods (0, 22, 36 and 53 days) in a chamber of 2 ∼ 7°C, then transplanted to three different conditions, i.e. PHY: 25–20°C day and night temperatures, 16 hours day length, GHL: 10 ∼ 25°C, 16 hours day length with supplementary light and GHN: 10 ∼ 25°C, natural day length (10 ∼ 15 hours). In PHY, FNC bolted and flowered with almost the same leaf numbers in all 4 different chilling treatments. This means that FNC has very low sensitivity and no requirement to low temperature for its reproductive growth. In GHN (short day length), FNC bolted very slowly. Then the bolting and flowering of FNC were promoted by both long day length and high temperature. The newly found bolting characteristics of ‘Osaka Shirona Bansei’ could be applied to breed unique slow bolting Chinese cabbage (B. rapa L. ssp. pekinensis) which might be non-sensitive to low temperature and its bolting and flowering would be induced with the combination of long day length and high temperature. Using the unique variety, it might be also possible to establish a new cropping type of Chinese cabbage (late autumn sowing, spring harvest).

Leaf morphology and soft rot resistance in offspring of a somatic hybrid between Chinese cabbage and kale (Cruciferae)

SummaryVariations in leaf morphology and soft rot resistance were investigated in offspring of a somatic hybrid between Chinese cabbage (2n=20) and wild kale (2n=18). Concerning leaf morphology, self-fertilized offspring of the somatic hybrid (2n=38) had a mean value intermediate between Chinese cabbage and kale in only one of the three indices used for comparison. Backcrossed offspring of the somatic hybrid with Chinese cabbage had intermediate mean values between Chinese cabbage and self-fertilized offspring of the somatic hybrid, but there was much larger variation within the backcross population. As to soft rot, Chinese cabbage was susceptible, and wild kale resistant. Self-fertilized and open-pollinated offspring of the somatic hybrid had intermediate mean values of the parental species and large variations of the symptoms. The backcrossed offspring were rather susceptible but showed continuous variation. In the backcrossed progeny, no correlation was observed between resistance and leaf morphology. It is hypothesized that recombinants having soft rot resistance from kale in combination with leaf morphology of Chinese cabbage will segregate in later generations.

Strawberry cultivar identification based on hypervariable SSR markers

We genotyped strawberry cultivars by two newly selected and two previously reported SSR markers. All four markers produced interpretable electropherograms from 75 accessions consisting of 72 Fragaria × ananassa cultivars or lines and three octoploid Fragaria species accessions. These SSR markers were highly polymorphic; in particular, one of the newly developed markers, FxaHGA02P13, was capable of distinguishing all of the accessions except for a mutant strain that was derived from another accession in the set. When two markers were combined, all 48 full-sib individuals could be distinguished. Fingerprinting patterns were reproducible between multiple samples, including the leaves, sepals, and fruit flesh of the same accession. Principal-coordinate analysis of the 75 accessions detected several groups, which reflect taxon and breeding site. Together with other available markers, these SSR markers will contribute to the management of strawberry genetic resources and the protection of breeders’ rights.

Correction to: Development of late-bolting F1 hybrids of Chinese cabbage (Brassica rapa L.) allowing early spring cultivation without heating

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