A thermo-sensitive seedling-colour mutant 7436S was detected in the field from a breeding nursery in China, in 1991. The experiments were conducted at artificially controlled temperatures (23.1°C, 26.1°C, 30.1°C) in growth chambers. The results showed that the seedling colour of the mutant 7436S was white (23.1°C), light yellow (26.1°C) and normal green (30.1°C) at 10 days after sowing and yellowish green (23.1°C) and normal green (26.1°C, 30.1°C) at 20 days after sowing, respectively. It was concluded that its thermo-sensitivity decreased gradually with the increase of the seedling age. In addition, its thermo-sensitivity for seedling colour was oriented, as white seedlings turned green at high temperatures, but not in the opposite direction. The segregation ratios in the F2 populations showed that a recessive nuclear gene (tentatively designated as tsc-1) controlled the thermo-sensitive seedling-colour character. Based on genetic linkage and the recombination value (34.1%) between the tsc-1 gene and short panicle morphological marker (sp) gene in the F2 generation, the results indicated that the tsc-1 gene was located on chromosome 11.
The S-genotype assignments in the Japanese pear cultivars, ‘Akaho’, ‘Tanzawa’, ‘Kimizukawase’, ‘Choju’, ‘Ichiharawase’ and ‘Meigetsu’ previously determined by pollination tests have raised some doubt recently. These cultivars were analyzed by S-RNase based PCR-RFLP, and their S-genotype assignments reconsidered. The assignment based on the PCR-RFLP system was in agreement with that determined previously by pollination tests in six cultivars, ‘Chojuro’, ‘Doitsu’, ‘Kikusui’, ‘Kosui’, ‘Taihaku’ and ‘Yakumo’, confirming the applicability of the system. ‘Akaho’, ‘Tanzawa’, ‘Kimizukawase’ and ‘Choju’ were analyzed and assigned as S3S5, S4S5, S1S5 and S1S5, respectively. Two of these cultivars, ‘Akaho’ and ‘Tanzawa’, were also confirmed by our pollination tests. In three cultivars, ‘Ichiharawase’, ‘Meigetsu’ and ‘Heiwa’ (‘Nijisseiki’×‘Ichiharawase’), a new S-RNase fragment with a size and digestion pattern distinct from those of S1 to S7-RNases of Japanese pear was amplified. The deduced amino acid sequence in the hypervariable region of this S-RNase was quite different from those of S1 to S7-RNases. We, therefore, assigned this S-RNase as S8-RNase, and identified the S-genotypes of ‘Ichiharawase’, ‘Meigetsu’ and ‘Heiwa’ as S1S8, S1S8 and S4S8, respectively.
A Sri Lankan indica rice (Oryza sativa L.) cultivar Babawee harboring a brown planthopper (BPH)(Nilaparvata lugens Stål) resistance gene bph4 was crossed as a male parent with two susceptible cultivars, either indica IR24 or japonica Tsukushibare. Segregation of the BPH resistance in the two crosses was studied by directly assaying the F2 phenotypes and by determining the F2 genotypes based on the F3 phenotypes. In both cross combinations, the segregation of the BPH resistance significantly deviated from the ratio expected for the single recessive gene model. Using bulked DNAs of homozygous resistant and susceptible F2s and the parents, seven out of 214 RFLP markers were selected as linked markers, of which six on chromosome 6 were common in the two cross combinations. Two microsatellite markers on chromosome 6 were also linked to bph4. Although the map position of bph4 could not be determined, the gene was assigned to the distal region of the short arm of rice chromosome 6 based on the bulked segregant analysis and linkage analysis.
We have constructed a linkage map of eggplant (Solanum melongena L.) using an F2 population derived from a cross between a breeding line, EPL-1 and an introduced line, WCGR112-8, from India. The two parental lines showed contrasting responses to several pathogens and differences in several morphological traits. Parental lines were screened with 1, 232 random primers for RAPD and 64 primer combinations for AFLP. The link-age map consisted of 181 loci, comprising 88 RAPD and 93 AFLP markers. These markers identified 21 linkage groups spanning 779.2cM with an average distance of 4.9cM. The linkage groups ranged from 1.9 to 95.6cM in length and included 2 to 32 markers, respectively. The fruit shape and color development trait were scored and the linkage to the markers was investigated. The fruit shape showed a significant association with markers on linkage group 2. Color development in fruit, stem and calyx showed a significant association with markers on linkage group 7. These markers may provide valuable information for eggplant breeding.
We produced near isogenic lines (NILs) for three purple leaf genes, Pl, Plw and Pli of rice with a genetic back-ground of T-65 to characterize each allele. Three NILs each had characteristic tissue-specific anthocyanin pigmentation. T-65 Plw was newly found to make the root purple when the root was exposed to light. To explore the inducible characteristics of the three genes, we examined the responses of the three NILs to UV-B irradiation. Although the accumulation of anthocyanin increased in all NILs with the increase in the intensity of UV-B irradiation, we observed differential responses for the accumulation of anthocyanin in the NILs: T-65 Pli accumulated the largest amounts of anthocyanin under weak and intermediate intensity of UV-B, though this NIL reduced anthocyanin accumulation under a high intensity of UV-B. T-65 Pl or Plw increased anthocyanin accumulation with increasing intensity of UV-B. Anthocyanin accumulation of the Pl NIL was higher than that of the Plw NIL under each intensity of UV-B. In addition, the total biomass of all the irradiated NILs decreased with the increasing dose of UV-B irradiation and the decrease was negatively correlated with the increase in anthocyanin accumulation in the dose range of UV-B irradiation.
The efficiency of Agrobacterium tumefaciens-mediated gene transfer in rice was improved by air-drying of the suspension-cultured cells. The suspension-cultured rice calli showed less efficient transformation mediated by Agrobacterium than usual calli cultured on the solid medium. However, simple air-drying of the calli suspension-cultured for 10 to 15min increased the transformation frequency 10-fold or more. The suspension cultures were established from the calli derived from mature rice seeds and subcultured every week. The frequency of transformation varied with the period of suspension culture and the size of the callus. The calli suspension-cultured for 4 weeks showed a higher transformation frequency than the control (not suspension-cultured), and the highest frequency was as high as 20%. However, the frequency was dramatically lowered by the extension of suspension-culture period up to 7 weeks or more. The transformation occurred frequently in the callus 1 to 2mm in diameter. Plant regeneration was observed in transformed calli suspension-cultured for 1 to 12 weeks, but plants abnormal in morphology and seed fertility were regenerated from the calli suspension-cultured for 7 weeks. In conclusion, rice calli suspension-cultured for less than 4 weeks were useful as targets of transformation mediated by Agrobacterium.
We postulates the phylogenetic relationships of section Sinomartagon using 64 Lilium taxa and two related taxa based on nucleotide sequence variations in the internal transcribed spacer regions of nuclear ribosomal DNA. Excluding the 5.8S unit, a total of 479bp were analyzed by three methods, i.e. maximum likelihood, maximum parsimony and neighbor-joining. Sinomartagon was polyphyletic and divided into five groups: (1) L. henryi, (2) L. henricii, L. macklinae, L. oxypetalum and L. nanum, (3) L. nepalense, (4) L. duchartrei, L. lankongense, L. amoenum, L. wardii and L. taliense, and (5) 10 other taxa of subsections 5a and 5b. This classification did not correspond to the subsections defined by Comber (1949), and all the groups should be recognized as distinct taxa. The second group which included mainly Nomocharis-like Lilium, should be treated as a different taxon such as section Lophophorum. Since the last group with section Dauricum and L. bulbiferum included L. davidii, the type of Sinomartagon, they could be considered to correspond to the true section Sinomartagon. The results provide a more convincing phylogenetic position for Sinomartagon.
Quantitative trait loci (QTL) associated with the allelopathic effect of rice (Oryza sativa L.) were identified using RFLP markers. The allelopathic effect was assessed by the growth inhibition of water-soluble extracts from the rice seedlings on lettuce seedlings. QTL analysis was carried out using the F2 population from the cross between an Indica type line PI312777 (highly inhibitory) and a Japonica cultivar Rexmont (less inhibitory). Seven QTL were identified on chromosomes 1, 3, 5, 6, 7, 11 and 12. One of the QTL on chromosome 6 had the largest effect on the expression of the allelopathic effect of rice and explained 16.1% of the phenotypic variation. The other six QTL explained the variation in the range from 9.4% to 15.1%. A multiple QTL model estimated that five QTL with LOD scores higher than 3.0 explained 36.6% of the total phenotypic variation. Digenic interactions in five pairs between the seven QTLs were detected.
We conducted a QTL (quantitative trait locus) analysis to identify the genetic characteristics of traits related to yield in rice, using 191 recombinant inbred (R.I.) lines derived from Milyang 23/Akihikari. We found that a QTL at the end of chromosome 1 clearly contributed to the spikelet number per panicle and spikelet number per unit area. One of the 191 R.I. lines, H8, showed a segregation of the spikelet number per panicle or per unit area in 1998. H8 was also heterozygous near the QTL. We determined the spikelet number per unit area and panicle number for 74 individual plants of line H8. An RFLP linkage map was constructed using data for heterozygous regions on chromosome 1 and other chromosomes. For the QTL analysis, this linkage map and the spikelet number data were used. The results showed that a QTL explaining 38.7% of the variance of the increased spikelet number per panicle was located neaer the RFLP marker R3192, at the end of the short arm of chromosome 1. This QTL was considered to be very effective in increasing the spikelet number per panicle; it originated from an indica variety, Milyang 23.