We analysed the fruit weight, flesh firmness, soluble solid content and pH of fruit juice to obtain information on the inheritance of these characters, using a Japanese pear seedling population consisting of sixteen families and their parental cultivars and selections. The average values for the fruit weight, flesh firmness, soluble solid content and pH of fruit juice in the parental cultivars and selections were 354 g, 4.5 Ibs, 12.4 % and 4.94, and t.he coefficients of variation for the fruit weight, flesh firmness, soluble solid content and pH of fruit juice in these cultivars and selections were 0.35, 0.09, 0.05 and 0.05, respectively. The average values of family means for three years in each family ranged from 202 g to 423 g for the fruit. weight, 4.3 lbs-5.1 Ibs for the flesh firmness, 12.3 %∼ 13.3 %for the solube solid content and 4.76-5.26 for the pH of fruit juice, with the overall average values of means of sixteen families for these characters being 272 g, 4.8 Ibs, 12.7 % and 5.05, respectively. The average value of the range of yearly fluctuations in each family was 47.2 g' for the fruit weight, 0.48 Ibs for the flesh firmness, 0.95 % for the soluble solid content and 0.12 for the pH of fruit juice. . Statistically significant parent-offspring correlation coefficients were obtained between mid-parental values and the values of family means for the fruit weight, flesh firmness, soluble solid content and pH of fruit juice, although they vvere different among the characters. The estimates of heritability for the fruit weight, flesh firmness, soluble solid content and pH fruit juice were in the range of 0.57 -0.82, 0.14- 0.56, 0.37- 0.50 and 0.58- 0.69. The average value of heritability for three years was 0.73 for the fruit weight, 0.29 for the flesh firmness, 0.42 for the soluble solid content and 0.64 for the pH of fruit juice. fruits

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The effect of the dwarfing gene from Dee-geo-woo-gen (in-dicated by d-47 in this study) on culm and internode lengths was investigated. Following isogenic dwarf lines were used : the two isogenic lines of d-47 of Shiokari and Taichung 65 (abbreviated to d-47 Iine and d-47(T65) Iine, respectively) ; and Calrose 76 (abbreviated to C76) which contains sd-1 at the same locus as d-47. Three Fl's be-tween the three dwarf lines and their respective parental cultivars, and two kinds of F2 populations were used. Two and three fertilizer levels were set for d-47 Iine and Shiokari, and d-47(T65) Iine and Taichung 65, respectively. The difference between d-47(T65) Iine and Taichung 65 in culm length was 28.0 cm under a condition of basal dress-ing, and the difference was 27% of the culm length of Taichung 65. Those between d-47 Iine and Shiokari were 27.0 cm and 38%. Those between C76 and Calrose were 20.0 cm and 19% . The difference in internode length be-tween each of dwarf lines and its parental cultivar became smaller from the first to 6th internodes.

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A shattering-resistance gene in the mutant line, SR-1 induced from an iudica, semidwarf rice variety, Nan-jingll was mapped on chromosome I using seven RFLP markers. It was also found that the shattering-resistance mutant gene was linked to a semi-dwarf gene, sd-1, derived from Nan-jingll. Eighty plants of a F₂ population derived from the crossing between SR-1 and a javanica rice variety, Dinalaga with shattering habit and long culm, were investigated for the degree of shattering, culm length and genotypes by RFLP markers. Although the segregation for the shattering degree and culm length was complex in the F₂ population, a significant correlation (r = - 0.57^* * ) between the shattering degree and culm length was detected. Thus the shattering resistance gene in SR-1 is likely to be linked to the semidwarf gene, sd-1, which has been mapped on chromosome I using RFLP markers(Ogi et al., 1993).

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Factors affecting the frequency of haploid production from the crosses of hexaploid wheat variety Chinese Spring and pearl millet line NEC-7006 were investigated. Wheat florets were pollinated with pearl millet at their developmental stages ranging from one day before anthesis to one day after anthesis. The embryos obtained were incubated on the culture medium with different combinations of hormones (indole-3-acetic acid and 6-benzylaminopurine) and solidifying agents (Gelrite or agar). The effects of developmental stages of immature embryos at the time of embryo rescue were also investigated in relation to plant regeneration. High frequency (25.4 % ) of embryo formation was obtained by the pollination earlier than the day of anthesis. Plant regeneration of the embryos was despressed on the culture medium supplemented with hormones. The lowest frequency of plant regeneration was found in the culture medium with combination of hormones and Gelrite. On the agarsolidified culture medium without hormones, immature embryos that were 0.7 mm long at 14 days after pollination regenerated into plants at a frequency of 54.4 olo .

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Twelve somaclones and the donor plant, male sterile alfalfa MSXC77-1, were compared for the pollen number, seed set and germination of hybrid seeds. For the pollen grain number, eleven out of twelve clones did not show significant differences from the donor plant. A cione which showed a significant difference in the pollen number produced fewer pollen grains on average than the donor throughout three trials. Six clones did not set seeds in selfing, and the donor and remaining six clones set less than 0.01 seed per flower. Seed set per flower in crossing with a male fertile genotype CUFIO1-56 exceeded 2.5 and no significant differences between the donor and somaclones were detected. Germination percentages of hybrid seeds between MSx C77-1 and CUF1O1-56 exceeded 900/0 in both the donor and somaclones after breaking treatment of hard seed. These results indicate that the variation in the somaclones was negligible and could be ignored for these charactcristics, and that tissue culture techniques can be practically applied to the clonal propagation of male sterile alfalfa.

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An F₁ hybrid plant of Petunia hybrida 'Violet' x 'White' produced a spontaneously mutated branch with leaves displaying white or yellow variegation on the margin. Morphological observation showed that the mutant had abnormal plastids which caused the white or yellow leaf color. The polypeptide pattern of the thylakoid protein in the variegated area differed from that in normal leaf and green area of the mutant. The data relating to selfing and backcrossing of the mutant with normal 'Violet' and 'White' showed that the abnormal plastids were almost totally maternally inherited, that is, the progenies from crosses with the mutant as female parent were almost all albino. However, variegated progenies were also occasionally observed when the mutant was used as the female parent. The results of this study suggest that normal chloroplasts were transmitted exceptionally from paternal parent or from green plastids occasionally kept in the generative cells of the maternal parent.

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Thirteen triploid hybrid lines of melon (Cucumis melo L.) were derived from crosses involving five tetraploid lines and seven diploid lines. Fertility and fruit characters of the triploid hybrids were assessed. When allowed to open-pollinate in field plots with adjacent diploid pollinators, eight triploid genotypes were sterile or nearly sterile (less than 1 o/o viable seed). Five triploid genotypes were partially fertile (viable seed 6-36 %). Staining and morphology of pollen grains from partially fertile hybrids indicated viable pollen grains were present. Cytological analyses performed on progeny of a partially fertile triploid plant fertilized by open pollination indicated euploid female gametes were common. Triploid hybrids between tetraploid 'Miniloup' and several other diploid parents had vegetative and fruit characteristics intermediate to the parents. Most triploid genotypes yielded round fruit. Sugar levels of some triploid hybirds were as high as diploid parents.

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To identify new earliness g'enes in rice, 15 isogenic earlyheading lines were bred after ten backcrossings, using 15 reciprocal translocation homozygotes (RT-Iines) produced from several varieties as donor parents of earliness genes, and Taichung 65 (T65) as a recurrent parent. Gene analysis for heading time in F₂ plants from the crosses of the early heading lines/T65, and in B₁F₁ plants from the crosses of the early heading lines/2 * T65 showed that each early heading line carried a dominant earliness gene. An allelism test between earliness genes harboured by these early heading lines and an earliness gene Ef-1 on the tenth chromosome disclosed that each early heading line carried an earliness gene at the Ef-1 Iocus. Out of 15 early heading lines, ten harboured earliness genes derived from ten RT-lines induced from the same cultivar Okute-Asahi.

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High cytokinin concentration medium induced multiple shoot. on thc basal part of the main stem generat.ed from cultured rice seeds. Hist:olog'ical observat.ions were done on sections of the basal part of main stem and showcd that multiple shoot originated from two types of bud - axillary buds from the primordium of tiller of the first leaf nodeand adventitious buds from the basal region of the first leaf. The adventitious buds were derived from epidermal and subepidermal cell layers on two fixed sites in the abaxial side of the base of the first leaf, where between these two sites the tiller of tho first leaf node could be found.

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A total of 19 isozyme loci were identified in selfed progeny of an open-pollinated variety, Chingen-sai (Brassica campestris L. var. chinensis ) and ·in F2 population of a hybrid between a selfed line of Chinese cabbage (B. campestl'is L. var. pekinen, sis ) and Mizu-na (B. campestlts I.. var. japonica ). Isozymes for acid phosphatase (ACP), esterase (EST), phos_phoglucomutase (.PGM), glutamate oxaloacetate transaminase (.COT) and leucine aminopeptidase (LAP) vvere resolved by polyacrylamide gel electrophoresis (PAGE), v, 'hile phosphoglucoisomerase (PGI) and peroxidase (POX) were by starch gel electrophoresis (SGE). In addi-tion, some selfed progenies from open-pollinated varieties were analyzed to confirm segregations at each isozyme Iocus. With the selfed progeny three sets of linked loci were found: ACP-2, PGM-2 and ACP-3; LAP-2 and GOT-1; GOT-4 and GOT-5. Among a total 12 Ioci analyzed in the F2 population, three sets of linked isozyme loci were found: ACP-8 and PCM-2; LAP-2, G.OT-1, EST-2 and POX-3; ACP-6 and EST-1. The linkages found among isozyme loci seemed to be useful to identif.v isozyme loci when their expression is variable. The information will be also useful in utilizing genome and maps of B. campestris L.

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The pollen tube growth in interspecific pollination was investigated to assess interspecific cross-incompatibility among ten species at the prezygotic stage and also to analyze the evolutional relationship between self-incompatible (SI) and self-compatible (SC) species. Total 136 pollination treatments were conducted under pollinator-free conditions at the full flowering stage. Florets were harvested 4 or 24 hours after pollination, and pollen tube length was measured under a fluorescent microscope. Measurements were made on the longest pollen tube for each style, and 6-36 styles were observed per pollination treatment. The following conclusions were derived from this study. 1) Unilateral incompatibility was observed among the SI and SC species. ing, it is important to analyze the relationship between 2) Dimorphic self-incompatibility system influenced the re-cross-incompatibility and self-incompatibility

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A method for Agrobacterium -mediated transformation of torenia (Scrophulariaceae) is reported. Leaf segments of torenia plants grown in vitro were infected with the Agrobacterium strain LBA4404 harboring a binary vector containing the neomycin phosphotransferase IIgene, P -glucuronidase (GUS) gene lvith an intron and hygromycin phosphotransferase gene. The infected explants were cultured on Murashige and Skoog medium supplemented with 1 mg/l benzyladenine, 100 mgfl carbenicillin and 300 mg/l kanamycin (selection medium) for regeneration. Twelve shoots out of 67 shoots which regenerated from green compact calli on the selection medium were GLTS-positive. Polymerase chain reaction analysis confirmed the presence of the GUS gene in the GUS-positive plants. Mendelian inheritance of the GUS activity in the progenies of the transformed plants was demonstrated.

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Buckwheat is considered to be one of the useful sources of rutin in food. To analyze the varietal differences and heritability for the rutin content in seed and leaf in common buckwheat, twenty seven cultivars and strains introduced from the major countries where buckwheat is cultivated were tested. Plant materials were grown in 1992 and 1993 in a randomized block design with two replications each year in the Experimental Field of Shinshu University. Rutin content in seed and leaf was determined by high performance liquid chromatography, and the main characters were also observed. The mean values of the rutin content showed a wide range of variation. The seed rutin content of the tetraploid cultivars of Japan was higher than that of the diploid ones. However, there was no significant difference between the ploidy level for leaf.

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For identification of random amplified polymorphic DNA (RAPD) markers tightly linked to Xa-1, which is one of the bacterial blight resistance genes in rice, a near-isogenic line (NlL) for Xa-1 and a recurrent cultivar were screened by RAPD primers. Two out of 280 primers produced DNA fragments tightly linked to Xa-1, namely U087₇80and Y03₇00. No recombinant was detected between Xa-1 and Y03₇00, indicating that this RAPD fragment was closely linked to Xa-1. Y037₀0 existed in IR-BB I and Kogyoku as a single copy sequence, but did not exist in IR 24. U08₇50 was linked to Xa I at a drstance of 1 4 ±1.4 cM. These RAPD markers will facilitate selection of Xa-1 for breeding and will be starting points of gene cloning based on chromosome walking in near future.

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There is great polymorphism in the polype.ptides speci-fied by Hor I and Hor2, and to determine the genotypes of hordein is considered to be important for breeding. At present, the hordein genotypes have been investi-gated by several researchers. But so far, Iittle has been reported about the hordein genotypes in Japanese culti-vars. Thus, we investigated and determined the hordein genotypes in Japanese cultivars. Our conclusions are as follows : 1) Three novel types of Hor I (Ch, Ta, Ka ), and two of Hor 2 (Sa, Ta ) were identified. 2) Most of the naked barley and the six-rowed uzu-type covered barley cultivars have alleles which are not found in European barley cultivars. On the other hand, two-rowed barley and six-rowed normal-type covered barley cultivars have alleles which are found in European bar-ley cultivars. 3) Many of the naked barley cultivars have identical alleles. Therefore, indentification of the naked barley cultivars based on hordein genotypes is not practical.

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We investigated the RFLP genotypes in 81 accessions of Japanese local and improved O. P. varieties using 4 genomic clones (P-023, P-051, P-061 and P-148 ) and one CDNA clone (C-143). Since four clones (P-023, P-051, P-061 and C-143 ) showed a high gene diversity among the varieties, we thought that these clones were avail-able for some purposes as genetic markers (Table 1). The materials used in this experiment were classified into some varietal groups and ecotypes. The distribution of RFLP genotypes in these groups and ecotypes were not randomized (Table 2). The differences in some agro-nomic characters were found between two varietal groups having the same RFLI) homozygotes, especially in C-143 Iocus (Table 3). The relationships among RFLP genotypes, ecotypes and characters in locus C-143 would be an important information to know the ori-gin of Japanese cucumber.

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Early maturity has been one of the important breeding objectives in wheat (Triticum aestivum L.) in the southwestern part of Japan, because this trait is suitable for double cropping with summer crops such as rice, and for avoiding pre-harvest sprouting which often occurs in the rainy season. However, early maturing cultivars are usually spring type cultivars which are prone to sustain frost damage in early spring because of their earliness in ear primordia initiation and stem elongation. To develop early maturing wheat cultivars with tillers that can avoid frost damage, winter type near-isogenic lines were bred for the extremely earlJ maturing spring cultivars Asakazekomugi and Salkal l07 (latel reg Istered as "Abukumawase") by backcrosslng to a winter type cultivar Ebisukomugi (Fig. l).

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Stomatal frequency is a character which can be easily and trans-handled in rice breeding. There were considerable differences in the stomatal frequency among the mutant lines . induced from a rice cultivar Kinmaze. A mutant line (CM 1290) which showed a high stomatal frequency was geneti cally analyzed. Two genes' were found to control high sto matal frequency.

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Colchicine was applied directly t.o ant.hers excised from thc flower buds of tobacco (.Nicotiana tabacu.m I..) just before the initiation of anther culture, and dip]oidization and development of microspores in thc colchicine-t, reated anthers were investigated. Anther culture response, which was defined as the percentag'e of anthers producing plant lets to the tot.al number of cultured anthers, decreased with the increase in both colchicine concentration and treatmont duration. However, high frequenciGs of diploid plants were obtained among tho plants derived from t.he anthers treated with colchicine. In particular, the hig'hest diploidizat.ion rat.e (66.7% ) was. obtained in the 0.4 % colchicine treat-ment for 8 h. Furthermore, neither ploidy chimera nor growth damage appeared in the generated plants.

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Fifty-eight durum wheat cultivars were selected from the introduced germplasm from the National Institute of Agro-biological Resources (Japan) in 1990. The selected cultivars were grown in Tunisia under rainfed conditions and in-vestigated on wield potential, number of seedslspike and thousand kernel weight for evaluation of their genetic variations and breeding potential during the 1992/93 grow-ing season. All characters showed relatively large standard deviations and coefficients of variations. Thus, this breed-ing material may be successfully used in Tunisian breeding programs targetting specific goals. Some cultivars per-formed similar to the most commonly grown local cultivars which were included in the experiment as checks. Selection was applied in order to select the best genotypes. Compared to the checks and based on yielding ability, 17 promising lines were identified.

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The use of a simple crossing method, named 'post-harvest pollination method' was examined. The point of this method is the utilization of panicles cut at internode m, below the node of the 2nd leaf from the flag leaf, as female parents. By this method it was possible to pre-pare receptive panicles on the day of crossing. After pollination, these panicles were able to grow only with water and to form seeds in the glass-house (Fig. 1). In some crosses using this method, the seed set percentage was lower than the *"eneral pot cultured pollination method' (Table 1). However, the post-harvest pollination method was more convenient b, ecause of its simplicity

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[in Japanese]

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We have recently developed a package of programs named MAPL which can be used for construction of DNA polymorphism linkage maps from segregatrion data in F₂, backcross, and dihaploid derived from a cross of two pure lines. The package allows the analysis of quantitative trait loci (QTL) . The programs are written entirely in N88-BASIC under MS-DOS operating system for an NEC personal computer and they can be easily modified to run on other home computers such as IBM-PC. At the present time the package is composed of 12 independently executable programs shown below ; MINP Accepts your RFLP, RAPD or trait data from the keyboard.

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