An RFLP linkage map was constructed using a BC1F3 population, which was developed by backcrossing between an elite Japonica rice variety, Koshihikari, as the recurrent parent and an Indica rice variety, Kasalath, as a donor parent. The map was constructed using data from 187 plants and 116 RFLP markers. Quantitative trait loci (QTL) analyses were carried out for days-to-heading, and culm, panicle, and internode lengths. Four QTLs (p<0.001) for days-to-heading, six for culm length, and four for panicle length were detected. Seventeen QTLs were detected for the internode length. Chromosomal locations of putative QTLs in this study were compared with those in other studies. Several QTLs for these traits, showing a correlation with phenotypic values, were mapped in the same chromosomal regions. However, the sets and relative effects of QTLs for internode length were different among the corresponding QTLs for culm length. The implications of QTL analysis in the BC1F3 generation for rice chromosome introgression breeding are discussed.
The variation of the chromosome number in interspecific progeny is difficult to predict. We defined the terms “fertilization fitness” and “relative fitness” as the parameters of competitive ability of the gametes and attempted to use them in a study on the variation of the chromosome number in the progeny between Brassica napus and B. rapa. Fertilization fitness was defined as the ratio of the actual frequency of the gametes with a specific chromosome number to the theoretical frequency based on binomial distribution. Relative fitness was defined as the ratio of fertilization fitness of the gametes with a specific chromosome number to fertilization fitness of the gametes with n=10. A resynthesized accession and a natural accession of B. napus were used in this experiment to produce sesquidiploids AAC-S and AAC-N, respectively. A comparative study on these two sesquidiploid populations was carried out to reveal differences in the pattern of variation in the chromosome number. Fitness analysis showed that gamete competition was conspicuous and closely related to the chromosome number. Gamete competition occurred predominantly during the embryo developmental stage. In both sesquidiploid populations, fertilization fitness decreased abruptly when the chromosome number varied in the range from n=10 to n=12 or in the range from n=19 to n=17. However, in the range from n=13 to n=16, the effect of the chromosome number on fertilization fitness was more pronounced in the AAC-N population than in the AAC-S one. The AAC-N population showed stronger tendency in keeping its gametes toward euploid number. Fertilization fitness and relative fitness was found to be efficient parameters for the study of variation of the chromosome number in interspecific hybridization. The use of the Relative fitness parameter may enable to predict the frequency of a specific chromosome number in interspecific progenies.
Leaf rust, caused by Puccinia triticina E., is an important disease of wheat in Japan. Thirty Japanese wheat (Triticum aestivum L.) cultivars, 7 Japanese supplementary differentials and a set of near-isogenic lines carrying named Lr-genes, were evaluated for resistance at the seedling growth stage with an array of Mexican Puccinia triticina races. The variation in seedling infection type of the cultivars was compared with that of the differentials, and genes conferring a low infection type were postulated. In total, nine named genes, viz. Lr1 (2 cultivars), Lr3 (3), Lr9 (4), Lr10 (5), Lr17 (1), Lr19 (1) Lr23 (8), Lr27 + 31 (3) could be identified/postulated in Japanese cultivars and supplementary differentials.
Self-incompatibility (SI) in Brassicaceae is sporophytically controlled by haplotypes of the polymorphic S locus complex. Two tightly linked polymorphic genes at the S locus, S-locus glycoprotein (SLG) and S-receptor kinase (SRK) genes, are specifically expressed in the stigma. S-haplotypes have been classified into class I and class II types based on the sequence similarity of their SLGs, and their SRKs. To investigate the effect of an antisense SLG gene on the class divergency of the endogenous SLG and SRK genes, we introduced an antisense class I SLG43 cDNA into a cultivar Osome in Brassica rapa which was heterozygous for class I S52 haplotype and class II S60. SLG43 is more similar to the endogenous SLG52 (87.8% identity) than to SLG60 (74.8% identity), Out of ten primary transformants analyzed, two were completely self-compatible; the SI phenotype of stigma was altered from S52S60 to S60, but that of pollen was not. In these two plants, the expression levels of mRNA and protein of SLG52 were reduced, whereas those of SLG60 were not. We suggest that an antisense class I SLG-transgene causes homology-dependent suppression, which leads to breakdown of the class I S-haplotype specificity in stigma but not the class II S-haplotype.
Two induced mutants for early heading in diploid species of Triticum monococcum and Aegilops squarrosa, A- and D-genome ancestral species common to common wheat, were analyzed for the genetic behavior of the heading trait. The T. monococcum mutant headed earlier than its wild type under the long-day condition with vernalization treatment, whereas the Ae. squarrosa mutant headed under the short-day condition without any difference from the long-day one. These results indicate that the former is a mutant for narrow-sense earliness, and the latter, for photoperiod sensitivity. Earliness of both mutants was found to be controlled by a recessive gene. These early-heading mutants could be useful sources for the breeding of heading earliness of common wheat, as well as for genetic analysis for the determination of heading time.
We investigated the QTLs for the enzyme activity and thermostability in β-amylase in barley using two doubled haploid line (DHL) populations. QTLs for the enzyme activity were detected on chromosomes 1H and 2H in the Steptoe/Morex DHLs and on chromosome 5H in the Harrington/TR306 DHLs, respectively. Some of these QTLs were close to the QTLs for the diastatic power and grain protein which represent malt quality characteristics. We observed two QTLs for the thermostability in the Steptoe/Morex DHLs. Position of one major QTL was the same as that of the β-amylase structural gene locus on chromosome 4H, suggesting that thermostability is controlled by multiple alleles of the locus. The other QTL with a negligible effect was located on the short arm of chromosome 2H. However, no QTLs were observed in the Harrington/TR306 DHLs because the difference in the thermostability value in the DHLs was not appreciable.
To establish DNA markers for ethylene-related genes in melon (Cucumis melo L.), we searched for microsatellite and cleaved amplified polymorphic sequence (CAPS) polymorphisms in two ACC synthase genes (CMe-ACS1, CMe-ACS2) and two ACC oxidase genes (CMe-ACO1, CMe-ACO3), and found two CAPSs and six microsatellite markers. Five markers were detected in two genes, CMe-ACS1 and CMe-ACO1, which were expressed during fruit ripening. A highly polymorphic marker was found in CMe-ACS2, where the number of simple sequence repeats (TA) was highly variable among cultivars, ranging from seven to thirty-seven. Insertion/deletion of (T)n and (A)n were also detected in CMe-ACS2. Specific CAPS and microsatellites for vars. makuwa and conomon, local varieties in East Asia, were detected in four markers, Acs1-c1, Acs2-ms1, Aco1-ms2 and Aco3-ms1, and could be useful markers for phylogenetic analysis in melon.
The present study was conducted to evaluate the factors (e.g. cultivar (V), wild species line (L), year (Y) and their interaction) affecting the production of a BC1F1 population (cultivar × F1(cultivar × ‘peruvianum-complex’)), a breeding strategy for using many cultivars as pistillate parents for the production of a BC1F1 population and for the segregation of some characteristics such as sweet aroma of leaf, morphological traits and self-incompatibility in the BC1F1 population. Ovule selection and culture method was used for the production of progenies. The interaction between the cultivar and the wild species line (V × L) was found to be significant. Differences in the number of GOFs (Germinated Ovules per Fruit) among 19 tomato cultivars crossed with F1 (cultivar × L. peruvianum LA1554) were significant. Differences in the number of GOFs among wild species lines (as F1 pollen parents) were also significant and much more pronounced than those of the cultivars. Significant variation was observed within-year and affected the interaction (V × Y) which was variable. The present study suggests that the probability of obtaining a stable, consistent average number of GOFs is high for the production of a BC1F1 population if many cultivars are used at a time as seed parents. The segregation of some characteristics in the BC1F1 population was evaluated. Most of the morphological traits resembled those of the wild species parents. Thirty six percent of the BC1F1 population inherited self-compatibility from the L. esculentum parent. A sensory panel composed of 8 members evaluated the leaf aroma of 100 BC1F1 plants (19 cultivars × F1 derivedfrom LA1554) and two BC1F1 plants were found to have the same sweet aroma as the F1 (pollen parent). In the present study a large BC1F1 population with an expected number of plants was obtained. Sensory attributes of some BC1F1 plants suggested that the expected quantitative trait had successfully been introduced into the BC1F1 population.
To investigate the genetic mechanism regulating crown root formation, we identified two recessive rice mutants (odm 202 and BRX334). The odm 202 mutant was detected in a MNU-mutagenized M3 population of rice (cv. Taichung 65) and the BRX334 mutant in a γ-ray mutagenized M2 population of rice (cv. Blue Rose). The number of crown roots of the odm 202 and BRX334 seedlings was significantly lower than that of the respective wild types and this mutation type was designated as crown rootless with the gene symbol crl. Allelism test indicated that the two mutant genes were not allelic and the CRL loci of odm 202 and BRX334 were designated as CRL1 and CRL2, respectively. Histological observations suggested that the initiation of crown root primordia was impaired in the crl1 mutant, while in the crl2 mutant both the initiation and subsequent growth of crown root primordia were impaired. In addition, the crl1 mutant grew normally until maturity except for the difference in the number of crown roots from the wild type, whereas the crl2 mutant showed many abnormal morphological characters besides the defect in the formation of crown roots. These facts suggest that CRL1 regulates specifically the initiation of crown root primordia but is not involved in the radicle and lateral root initiation or shoot development, while CRL2 regulates various processes of plant development.
In the first step of pollination in tobacco, pollen grains attach to the stigma exudate, which we previously found to contain two major stigma-exudate proteins, SE32 (32kDa) and SE35 (35kDa) (Kuboyama et al. 1997). In the present study, we determined each N-terminal amino acid sequence. The N-terminal amino acid sequence of SE32 was identical to that of PPAL, a stigma specific protein which was similar to grass pollen allergens and β-expansin. However, no sequences identical to the N-terminal amino acid sequence of SE35 were found in the protein databases. An antiserum raised against SE32 was found to react with both SE32 and SE35 in SDS-gel blot analysis. SE32 was detected only in the stigma, while SE35 in both the stigma and the style. These two proteins were not detected in other floral or vegetative organs. Immunohistochemical analysis showed that the antigens of the anti-SE32 antiserum were localized in the extracellular space of transmitting tissue. Accumulation of SE32 started in the completely elongated bud and increased with flower maturation. However, accumulation of SE35 was already detected in the young bud. The antigenicity of SE35 to anti-SE32 antiserum showed structural similarity between SE32 and SE35, and SE35 might belong to the same protein family as SE32. SE32 and SE35 might soften transmitting tissue of the stigma and style, and they might play a role in the elongation of the transmitting-tissue cells or the penetration of the pollen tube into the tissue.
Tissue culture and histological studies were done to ascertain the effects of benzyladenine (BA)-preconditioning on direct shoot regeneration from cotyledonary node explants of mungbean. The highest direct shoot regeneration (93.3%), double-sided shoot initiation (65.0%) and average number of shoots per explant (2.7 shoots) were obtained when Pag-asa 7 explants are excised from seedlings germinated in basal medium (BM) consisting of MS salts and B5 vitamins with 1.0mgl-1 BA, and subsequently cultured in fresh medium of the same composition. Histological inspection of sections from germinating seeds in BM and BM+1.0mgl-1 BA sampled at 1 to 4 days from germination revealed bigger and developmentally more advanced axillary shoots in BA-preconditioned seedlings, a built-in advantage which could attest to the improved regenerability in BA-treated seedling explants over the control (BM only). During shoot initiation from explants, two treatments namely doubling of the concentration BA to 2.0mgl-1 and the addition of a non-ionic surfactant, Pluronic F-68 did not further increase the responses, but gave results comparable with those obtained using BM+1.0mgl-1 BA alone. Conversely, a BA-thidiazuron (TDZ) combination (each at 1.0mgl-1) when added to BM significantly reduced shoot induction to only 48.3% possibly due to increased callusing at the nodes in 55% of the explants. The importance and applicability of the regeneration system in tissue culture and/or genetic manipulations of mungbean and other Asiatic Vigna species is discussed.