The frequency of occurrence and types of branching spikes and spikelets were examined in one octoploid and eleven hexaploid lines or varieties of triticale (X Triticosecale WITTMACK). Among the plants sown in five different months, i.e., February, September, October. November and December 1986, the plants sown on September 10, as a whole, showed the highest frequency of branching. This phenomenon may be attributed to a daily mean temperature as low as about 5°C at the time of ear formation that provides long period for inflorescence development which gives favourable time for bh (branching) gene to be active longer for branched development. The sensitivity to low temperature seemed to differ from one to another variety or line in triticale. Octoploid line Tcl 18 showed a higher frequency of branching than the hexaploid ones. Commercial varieties of hexaploid triticale including Welsh, Rosner, Yoreme and Currency did not show any type of branching. The varietal difference in the frequency of branching was not clearly associated with the chromosome constitution or cytoplasrnic characteristics of the lines or varieties. Branching occurred mainly on the lower 1/3 of the spikes. Branching spikes with hay-fork shape, Y-fork shape, and branching from the flag leaf node as well as branching spikelets of banana twin type, face to face twin type, compact type, whorl and square head types were recorded. The number of spikelets per spike and the number of florets per spike in most of the branching spikes were significantly larger. The number of grains per spike in the branching spikes of the octoploid line Tcl 18, hexaploid varieties Beaver, Rosner (Mono-1B) and Beagle was significantly larger than of the normal spikes, but opposite results were obtained for the hexaploid varieties Camel/Pato, Camel and Bronco. This observation suggests that it may be possible to select a high yielding line with a large number of spikelets, florets and grains per head in triticale.

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In order to clarify the inheritance of the semidwarfness of a Chinese variety Ai-Jio-Nan-Te (AJNT), two semidwarf near-isogenic lines of a variety Norin 29, SC-AJNT and SC-TN1, were developed through recurrent backcrosses. SC-AJNT exhibited the semidwarfness and shattering habit derived from the donor parent AJNT, while SC-TN1 exhibited the semidwarfness of a variety Taichung (Native) 1, which was proved to be controlled by the semidwarfing gene sd-1. SC-TN1, as well as Norin 29, showed non-shattering habit. The genetic analysis of culm length in the cross of SC-AJNT/Norin 29 demonstrated clearly that the semidwarfness of AJNT is controlled by a single recessive gene. Allelism test between the semidwarfing genes of SC-AJNT and that of SC-TN1 revealed that AJNT has a semidwarfing gene at the same locus as that of sd-1. The shattering habit of SC-AJNT was found to be controlled by a single recessive gene. The existence of a linkage relationship between the semidwarfing gene and recessive shattering gene was observed in the F₂ of the cross SC-AJNT/Norin 29 and BC₁ of the cross SC-AJNT/Norin 29//SC-AJNT. The recombination value was estimated 13.7±4.6%.

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Thirteen dwarf lines of rice each with a known dwarfing gene were subjected to extraction of endogenous gibberellins (GAs). Six dwarf lines for which gene analysis is not yet done, were also tested for their GA content. The amounts of GAs estimated were compared with the data obtained previously. Tan-ginbozu (d-35(t)) was the only mutant that produced almost no GAs. Level of endogenous GAs in induced autotetraploid lines of two rice cultivars was compared with corresponding diploid plants in their seedling stage. Induced autotetraploid lines had about one seventh or one eighth of the corresponding diploid lines in GA content. The growth rate of seedlings was slower In induced autotetraploid plants.

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Yukara dwarf and Fukei 71 are dwarf mutants of different origins, which are characterized by a strong lodging resistance. Genetic experiments in this study indicated that the dwarf gene of Fukei 71 is the same as or allelic to d-12 of Yukara dwarf. A specific response to high temperature was observed in both Fukei 71 and the d-12 isoline (recurrent parent is a cultivar, 'Shiokari'): the internode elongation was depressed when average temperatures exceeded 26°C. Through the effect of d-12, the third (from the uppermost) to fifth internodes were markedly shortened, resulting in lower positions for the developing panicles of the d-12 isoline than for those of Shiokari. When cool weather occured, the developing panicles of the d-12 isoline were protected under the surface of the irrigation water warmer than the air while the most of the spikelets of Shiokari became sterile owing to the cool air. Under a normal condition, however, the yield of the d-12 isoline was somewhat lower than that of Shiokari owing to the decrease in the number of spikelets per panicle.

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The degree of stomatal aprture is one of the irnportant characters which control the photosynthetic rate. The degree of stomatal aperture was measured for the rice mutant lines induced from a cultivar Kinmaze by the infiltration method at the adult stage. There was a considerable difference among the mutant lines in the degree of the stomatal aperture of the leaf blades. The degree of stomatal aperture at the young panicle differentiation stage was correlated with that at the heading stage (r=0.65***). The degree of stomal aperture was also correlated with the stomatal conductance (r=0.73***), which was reported to be highly correlated with the photosynthetic rate. A mutant line (CM 1787) which showed the highest score for the stomatal aperture was used for a genetic analysis. A single recessive gene was found to control the high score for stomatal aperture.

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Seed polymorphism of Echinochloa weeds in alcohol dehydrogenase (ADH), which has a critical function for the paddy weeds to germinate under flooding, was studied in the 196 individual accessions of the paddy and upland weeds collected in natural populations. The ADH zymograms detected in seeds were highly polymorphic and classified into five types; A₃, A₁A₂A₃, A₁A₃A₅, A₃A₄A₅ and A₁A₂A₃A₄A₅. The majority of each species and varieties had a specific zymogram; E. oryzicoloa, A₁A₂A₃; E. crus-gall var. formosensis, A₁A₂A₃A₄A₅; E. crus-gell var. praticoloa. A₃. E. crus-galli var. crus-galli having a widespread habitat had somewhat varied zymograms. The F₁ seeds obtained from reciprocal crosses between E. crus-galli var. formosensis (A₁A₂A₃A₄A₅, a paddy weed) and var. praticola (A₃, an upland weed) had A₁A₂A₃A₄A₅, and the observed segregation ratios of the F₂ seeds derived by selfing F₁ plants fitted to the two gene segregation mode of 9:3:3:1 for A₁A₂A₃A₄A₅:A₁A₂A₃:A₃A₄A₅:A₃. No distinct relationship was found between anaerobic seed germinability and ADH zymograrns of Echinochloa weeds collected in the natural populations. None of the accessions with A₃, however, showed anaerobic germinability whereas the others with either A₁A₂A₃ or A₁A₂A₃A₄A₅ did in E. crus-galli var. praticola.

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A bayesian approach for estimating genetic parameters of quantitative traits, such as heritability and genetic correlation coefficient, was evaluated. In this estimation procedure, prior information on genetic parameters to be estimated (such as the proper ranges e.g.[0, 1] for heritability and [-1, l] for genetic correlation coefiicient) was used in the construction of prior distributions of the bayesian procedure, where the joint posterior distribution of the parameters was obtained by replacing the other parameters as the phenotypic mean, variance and covariance with their classical estimators. Processing the expectation of each of the genetic parameters in relation to the joint posterior distribution by numerical integration gave the bayesian estimators. We call this bayesian method 'hybrid bayesian estimation' and its estimator 'hybrid bayesian estimator' as a combination of 'bayesian' and 'classical' method was used. Statistical properties of hybrid bayesian estimators with classical and modified ones, which are obtained by setting the classical estimates beyond the proper ranges to the nearest bound values, were investigated in the case of one trait and two traits using Monte-Calor sirnulations. In the case of one trait, where only the heritability is of interest, simulations were carried out for two values of the heritability 0.2 and 0.8, while the phenotypic mean and variance were fixed at 0 and 1, respectively. It was shown that hybrid bayesian estimators have smaller m.s.e.'s (mean square errors) than classical and modified ones. In the case of two traits, where two heritabilities and a genetic correlation coefficient of two traits were jointly estimated, simulations were carried for two cases, first two heritabilities and a genetic correlation coefncient of 0.8, 0.2 and 0.0 and secondly 0.8, 0.2 and 0.5, respectively. The phenotypic mean vector and variance-covariance matrix were set at 0 and I₂ (2×2 identity matrix), respectively. Simulation results showed that for heritabilities, as in the case of one trait, hybrid bayesian estimators were superior to classical and modified ones while for the genetic correlation coefficient, the superiority of hybrid bayesian estimators was even more conspicuous. Therefore it is concluded that hybrid bayesian estimators of genetic parameters are superior to classical and modified ones and can be very useful in practice.

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In studies of resistance of rice cultivars (Oryza sativa L.) to bacterial blight (BB) of rice caused by Xalethomonas campestris pv. oryzae, results from different countries could not be compared with each other, since different cultivars and/or different bacterial races were used in each counry. Therefore, it was necessary to re-analyze key cultivars using a uniform set of races, and to compare the results of previous studies from each country. For this purpose, we initially tested the usefulness of the clipping method of inoculation for genetic analysis of resistence in rice cultivars to BB in Japan. There was no previous report on genetic analysis in Japan using the clipping method of inoculation. We then analyzed rresistance in Japanese differentials, Chugoku 45 and Java 14 using Japanese and Philippine races of BB under a collaborative project between the International Rice Research Institute (IRRI), Philippines and the Ministry of Agriculture, Forestry, and Fisheries (MAFF), Japan. The clipping method of inoculation was useful for genetic analysis of resistant cultivars. In addition, we found Chugoku 45, Zenith, Himekei 16, Ortiglia, Zenith G713, Amareriyo, X-46, and Chukei 314 carry the gene Xa-3 originally found in Wase Aikoku 3 while X-43 has an additional major gene which is different from the Xa-3. Cultivars Akishinomochi and Nakashin 120 appear to have minor genes for resistance. The results of genetic analysis at IRRI and at Tropical Agrlculture Research Center (TARO) show that Chugoku 45, Java 14 and Wase Aikoku 3 are resistant to Phillppine races 1, 2, 3 and 4 as. well as to Japanese races.

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Fusarium head blight or scab caused by Gibberella zeae is an important disease of barley and wheat grown in regions where the humidity is high at the heading to ripening stages. Using about 5, 000 barley varieties, the author and Heta (1989) tested the reaction to Fusarium head blight for screening resistant varieties, and found remarkable varietal differences in the resistance. In the present report the results of genetic studies on the resistance by means of selection response and parent-offspring correlation are outlined. To evaluate the resistance of the plants, three spikes attached to their flag leaves were cut from each plant at the flowering stage and inoculated with an ascospore suspension of Gibberella zeae, maintained for 8 days under controlled conditions of light, hurnidity and temperature. The score of resistance of each plant was determined based on the percentage of infected spikelets as shown in Tables 1 and 2.

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Two semidwarf mutant breeding lines, Hokuriku 100 and Kanto 79, which were induced from a Japanese rice variety Koshihikari by gamma-ray irradiation, were analyzed for their semidwarfing genes. Compared with the original variety, Hokuriku 100 and Kanto 79 have 30 and 40% reduced culm length, respectively, and the latter flowers earlier by 10 days. The F₁, F₂ and F₃ generations of three crosses, Koshihikari×Hokuriku 100, Koshihikari×Kanto 79 and Hokuriku 100×Kanto 79, were grown for genetic analysis. In each cross combination, several F₁ plants, 223 to 334 F₂ plants and 100 F₃ lines which were raised from randomly selected F₂ plants were examined for culm length, heading date and seed fertility. It was clarified that the semidwarfism of Hokuriku 100 is controlled by one recessive semidwarfing gene (tentatively sd(t)) which was induced in Koshihikari, and this semidwarfing gene could not manifest itself until a gametic-lethal gene of Koshihikari (tentatively lt), which is inherited independent of sd(t), mutated to its non-gametic-lethal allele (tentatively lt^m). The semidwarfism of Kanto 79 proved to be due to the pleiotropy of one recessive early-heading gene (tentatively eh^e) which was induced in Koshihikari. This gene was nonallelic to and independent of the above two genes sd(t) and lt, and had no interaction with the gametic-lethal gene lt. These experimental results suggest that in the cross breeding to introduce the semidwarfing gene of Hokuriku 100 into some varieties or strains, a much larger number of offsprings are needed than in usual, and that the breeding aiming at early maturity as well as semidwarfism, Kanto 79 can be adopted as an excellent cross parent. The facts that the semidwarfing gene detected in Hokuriku 100, sd(t), did not influence any agronomic characters other than culm traits and did show a unique interaction with a garnetic-1ethal gene, and the evidences that sd(t) is non-allelic to d-47 as well as to sd-1 and d-49(t), indicate that sd(t) is the gene different from all the semidwarfing and dwarfing genes so far reported. So, the authors have designated this newly detected semidwarfing gene as d-60.

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