The mean values of anther length, stigma length and the number of pollen grains per spikelet were significantly lower in Japanese cultivars than in Indica and Javanica varieties. Days from transplanting to heading and the mean temperature during 30 days before head-ing were positively and significantly correlated with the anther length and the number of pollen grains per spikelet which were highly correlated each other, but were not correlated with the stigma length and spikelet length. The spikelet length, however, was positively and significantly correlated with the stigma length, anther length and the number of pollen grains per spikelet. Genetically improved parental strains to raise hybrid rice varieties of Japoleica type adaptable for cool area wlll be developed by introduc{ng efficient genes for floral characteristics from Indica and/or Javanica varieties into Japanese cultivars.

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Using materials differing in heading response from the previous study (TAKEI and SAKAMOTO 1987), the variations in the effects of daylength and temperature on floral initiation and panicle development in foxtall millet (Setaria italica P. BEAUV.) were investigated. Type I strains, those from Europe and Afghanistan, initiate the floral buds without short-day stimulus. In these strains, floral initiation rather depends on the degree of vegeta-tive growih, although panicle development is accelerated by short-day and high temperature conditions. The number of days to heading depends consequently on temperature conditions. Strains from Okinawa, Batan Is., and Lan-Yu Is. which showed sensitivity to daylength, did not necessarily need short-day stimulus for panicle initiation, but panicle development was accelerated by short day. Type II strains, those from low latitudinal areas have a long basic vegetative growth period and the duration of this period is reduced by high temperature conditions. In addition, these strains need many cycles of short-day to induce the floral buds. The requirement of short-day cycles for floral initiation and morphological development is reduced by aging. The heading of the strain from Halmahera Is. (2°N), the representative of Type II, is accelerated by 10 hrs. of light, but floral initiation does not necessarily take place as a response to the subtle change of daylength of this low latitude locality. The strain from Thailand is sensitive to a wide range of daylength. It should be identified as the fourth type, Type IV, characterized by a long basic vegetative growth period and high sensitivity to daylength. The strains from the Temperate Zone are sensitive to changes of daylength. The strain 403, from Kochi Prefecture, which is a representative of Type III and is an obligate short-day plant, shows a striking response to daylength only one week after sowing, and only a few cycles of short-day stimulus are enough for floral inductlon.

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Thirty one rice varieties representing five amylose categorles were grown under four different controlled temperature conditions in the IRRI Phytotron to stucly the effect of temperature during grain development on the amylose content, gelatinization temperature, and gel consistency. Stability analysis revealed predominance of linear component of variety-temperature interaction for all the three components. In general the amylose content decreased with increasing temperature. All the variety in the waxy group and majority of those in high amylose group showed absence of variety-temperature interaction for amylose content. Varieties in the very low, Iow and intermediate categories were either responsive or unstable. Similarly for gelatinization temperature and gel consistency also a number of varieties showed absence of interaction with temperature, some were responsive and others unstable. Waxy varieties IR29 and Malagkit Sungsong and high amylose variety IR42 were found to exhibit no interaction with the temperature for all the three quality components. Implications of the study on breeding strategy are discussed.

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Both biochemical and morphological characters were examined in 85 Japanese cultivars of taro (Colocasia esculenta ) to analyze the phylogenic relationships. Acrylamide gel electrophoresis of the tuber proteins revealed five patterns, designated as E, I, D, T, and A, for the major cultivars. Additional three patterns were found in the minor cultivars. Cluster analysis of taro cultivars based on 40 morphological characters was also performed. The results which were in agreement with those of the above-mentioned biochemical analyses, enabled to identlfy seven groups, i.e. Eguimo, Dodare (Dotare), Hasubaimo, Ishikawa-wase, Kurojiku, Akame, and Tonoimo groups, for the non-fasciculated taro cultivars, while two, Yatsugashira and Shogaimo groups for the fasciculated ones. The Yatsugashira group showed elec-trophoretic patterns common to the non-fasciculated Tonoimo group. Similarly the Shogaimo and Dodare groups exhibited a common electrophoretic pattern. The fasciculated cultivars are, therefore, assumed to be derivecl from the corresponding non-fasciculated cultivars by bud mutation. The Kurojiku group may be at the origin of the Ishikawa-wase group, since these two groups showed a common electrophoretlc pattern. The phylogenic and morphological relationships between the Hasubaimo and Dodare groups were also discussed.

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5-methyltryptophan (5MT) resistant cell lines, SAR-1, SAR-2 and SAR-3 were selected from anther derived calli of rice (Oryza sativa L. var Sasanishiki). Among these selected cell lines, two (SAR-1 and SAR-3) were stable in 5MT resistance and accumulated free tryprophan at least 50 times higher than that of the unselected cells. The resistant cell lines, however, were not able to produce plants on regeneration medium. Protoplasts from SAR-3 suspension culture cells were fused using dextran method with protoplasts of 5MT sensitive cells (Oryza sativa L. var. Hanahikari) which had the ability to regenerate plants. Prospective somatic hybrids were selected by culture on selection medium contianing 5MT and then on regeneration medium for plant formation. Three albino plants suspected to be somatic hybrids were regenerated from selected colonies. Calli, initiated from the plants, showed resistance to 5MT intermediate between that of the two parents. These results indicate that the combinaion of 5MT resistance ancl plant regeneratlon ability can be used as a complementary marker for selection and identification of somatic hybrlds in rice plants.

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The present study was carried out to determine the reason for the difficulty in developing common wheat varieties as early as the barley varieties with early maturity. When thirty varieties each of wheat and barley including early and late types were sown outdoors in the fall at Kurashiki, the double ridge stage (T1) of ear primordium differentiation in wheat was markedly retarded compared with that in barley. In spite the lack of difference in the onset of stem elongation (T2) between wheat and barley, in the case of the wheat varieties the time of heading (T3), anthesis (T4) and maturation (M) occurred later than in barley. T1 was most closely related to the heading time in wheat while in barley T2 was. In both wheat and barley, however, T3 was most closely related to M. Differences in the duration of the kernel filling period between wheat and barley were studied using 7 varieties each. Since the wheat varieties always required 3 to 5 days more for kernel filling than those of barley regardless of anthesis time, the accumulated temperature at 9 a.m. during the filling period was 200°C or higher in the wheat varieties than in the barley ones. The results analyzed further with two representative varieties each of wheat and barley indicated that in the barley varieties the rates of increase of the harvest indices were high immediately after anthesis, in contrast to wheat in which the rates of increase were rather low until two or three weeks after anthesis. About the same tendencies were recognized in the rates of increase of 1000 kernel weight in barley and wheat. Furthermore, the straw weight of the barley varieties decreased linearly with the increase in the number of days after anthesis, while in the wheat varieties, the straw weight did not change during the 20 to 30 day period after anthesis. These facts suggest that the differences in the duration of the kernel filling period between the wheat and barley varieties may be due to differences in the translocation of photosynthetic substances from stems and leaves to kernels. This may be the main constraint on the breeding of wheat dultivars as early in maturity as the barley ones.

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To clarify the physiological reasons why the two lowland weeds cannot invade into a dry habitat, drought resistance among Echinochloa weeds was compared by exposing potted plants to a progressive drought condition after drainage. Drought resistance markedly differed between the two lowland weeds, E. oryzicola and E. crus-galli var. formosensis, and the upland weed, E. crus-galli var. praticola in every aspect determined. E. crus-galli var. crus-galli having a widespread habitat from lowland to upland was always intermediate between them. The midday leaf water potential decreased similarly in all the weeds as the drought con-dition progressed, but in the lowland weeds it dropped to -23 bars while in upland weed to -15 bars on the 6th day after drainage. All the weeds showed wilting symptoms such as leaf rolling and senescence of the lower leaves, but the upland weed showed much milder symptoms than the other weeds. When compared to the lowland weeds at the same midday leaf water potential of -15 bars, the upland weed had 10 times larger stomatal resistance, 7 times smaller transpiration rate and 5 times larger leaf growth rate in length. The ratio of photosynthesis to transpiration measured on the 5th day was exclusively higher for the upland weed. The lower drought resistance of the two lowland weeds, which relates to their dull response of stomata to decreasing leaf water potential, is suggested to be one of the physiological reasons why they cannot invade into habitats with dry condition.

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Two cultivars, 'Aokuwai' and 'Shirokuwai', of Chinese arrowhead, Sagittaria tnfolia var. edulis (SIEB.) OHWI, were treated with solutions of 30 and 300ppm of gibberellic acid (GA₃) to promote the production of inflorescences. Inflorescences were induced in both cultivars by the GA₃ treatments as well as in the control in the case of 'Shirokuwai'. The inflorescence consisted of a raceme or compound raceme. Flowering in the GA₃-treated 'Aokuwai' began six weeks after planting while seven weeks in 'Shirokuwai'. However, in the control plants flowering started 21 weeks after planting. The percentage of plants with racemes and the number of racemes per plant were higher for the 300ppm treatment than for the 30ppm one. The length of the flower stalks and racemes, and number of male and female flowers per raceme varied among the treatments. The flowers were complete and the pollen stainability rate with an I₂-KI solution exceeded 90% in the 300ppm treatment in the two cultivars. Many fertile seeds were produced by open pollination. Based on the results obtained, it was concluded that the GA₃ treatment at 300ppm was more effective in promoting the production of inflorescences as well as the production of fertlle pollen and seeds in Chinese arrowhead than that at 30ppm GA₃. The seeds displayed dormancy, which was broken by field storage for two months. Seed germination was promoted in the light compared with darkness. These findings may contribute to the development of methods for cross-breeding of Chinese arrowhead.

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The effect of changes in temperature and radiation at the heading and flowering stages on the percentage of perfect grains of rice plants (cv. Fujiminori) was examined under various combinations of constant temperatures (22.5, 20.0, 17.5, 15.0, 12.5 and 10.0°C and alternating temperatures (daytime(12 h.)-nighttime(12 h.): 22.5-17.5, 20.0-15.0, 17.5-12.5, 15.0-l0.0, 12.5-7.5 and 10.0-5.0°C), and radiations (15.4 and 5.5MJ/m2/day) in growth cabinets in plants of various repening stages from heading day. The cool damage at the heading and flowering stages was closely related to the decrease of the radiation, and was ascribed to the decrease of the mean temperature rather than to that of the maximum and minimum temperatures. The critical low temperature from heading of which the rice plants could ripen with 80% of perfect grains was higher under low radiation (5.5MJ) than under normal radiation (15.4MJ). The cool temperature damage at the heading and flowering stages was higher of constant temperatures than of alternating temperatures. The effect of growth duration of rice plants on the critical temperature for ripening from heading was examined under low radiation conditions and at different levels of constant low temperatures. It was revealed that the critical low temperature from heading was not affected by the growth duration of the rice plants. In this experiment, rice plants with different growth durations were grown under controlled growth conditions (10h. short day and 25°C) for panicle initiation seedling at different leaf ages.

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Sprouting damage in wheat usually occurs at the ripening stage which coincides with the rainy season in Japan. The attempts to test a great breeding lines for sprouting resistance have not been successful. The objectives of our studies were to develop effective testing methods for the selection of lines with pre-harvest sprouting resistance and analyze the genealogical pedigree of resistant cultivars in wheat. In the first part of the study, the sprouting percentage immediately after sampling was found to be high at 35 and 55 days after heading (DAH), and low at 45 DAH (near maturity) except for Saitama 27, while the sprouting percentage one month after sampling increased with the number of days after heading (Fig. 1). The sprouting percentage depending on the storge conditions among 19 cultivars increased in proportion to the storage ternperature, namely, in the order of -16°C0°C16°CRoom. The sprouting differences observed immediately after sampling were significantly correlated with the 0°C (r=0.691^**), 16°C (r=0.489^*), room (r=0.550^*) storage conditions for 1 month and room storage conditions for 2 months (r=0.628^**), but were not correlated with the O°C and 16°C for 2 months among 19 cultivars. The sproutng performance at different ripening stages under constant ternperature testing conditions (17°C) and alternating temperature testing conditions (25°C in day time for 12 hrs. and 15°C at night for 12 hrs.) was very similar but the sprouting percentage under the constant temperature testing conditions was higher than that under the alternating ones (Fig. 2). The sprouting differences among cultivars immediately after sampling were observed at 14 days after simulated rain treatment, while at 6 days after simulated rain treatment in stored spikes (Fig. 3). A significant correlation was observed between sprouting immediately after sampling and sprouting of spikes wrapped with wetted filter paper (filter paper wrapping method) under different testing temperatures (16°C, 21°C, 26°C, 31°C, 26°C+16°C).

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Protoplast fusion and culture of alfalfa, Medicago sativa L. and birdsfoot trefoil, Lotus corniculatus L. were examined. Protoplasts of birdsfoot trefoil were treated with 5 mM iodo-acetamide to inhibit cell division, and protoplasts of alfalfa which divided at the early stage of culture, but could not form colonies were used. It was expected that only heterokaryotic protoplasts may form calli. However, only two calli obtained through protoplasts fusion using polyethylene glycol (PEG) showed different characteristics from those of either parent, while most of the calli showed characteristics of birdsfoot trefoil. One of these calli was found to be a somatic hybrid based on isozyme analysis and chromosome observation. However, hybrid plants have not been regenerated from the calli.

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Callus of carrot (Daucus carota L.) was dried for about 6 hours at 27°C in tall petri dishes containing silica gel. The water content of dried calli was around 3%. After storage for four days at 27°C in the dry state, they were transferred directly to MURASHIGE and SKOOG's agar medium (MURASHIGE and SKOOG 1962). Survival rate was as high as 90% as determined by callus growth and embryo and plantlet differentiation in 21-day cultures. The significance of the successful retention of differentiation potentials in dried callus is discussed in relation to conservation of plant genetic resources.

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Analysis of restriction fragment length polymorphisms (RFLPs) revealed that there was at least 3 types of high pI α-amylase multigene families in barley. It was estimated that the isozyme banding patterns detected by the isoelectric-focusing (IEF) method were not directly determined by these 3 types of structural genes, but affected by a regulatory gene (or part). It was assumed that there was a linkage between the structural genes and the regulatory gene, but new combinations of the structural gnes and the regulatory gene could be produced by genetic recombination. The bred lines with the new isozyme banding patterns may have resulted from the new combinations of the genes.

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In rice, gene pollution may occur when genes that control undesirable characteristics are integrated by natural hybridization. These genes are spread out when the seeds fertilized with alien pollen are used as seeds for the next generation, or when they fall oft the mother plant before the harvest and grow as weeds in the field. Once gene pollution has been spread by farmers', all the products harvested from the polluted fields lose their commer-cial value. Moreover, seeds kept for sowing the next generation must be replaced by new ones. Thus the financial damage is serious. As weedy offtypes that fall down in a field invade neighbouring fields, the pollution spreads more extensively. In fact, red rice cultivars, which have been the most harmful weeds in paddy and upland rice fields in parts of Japan frequently pollute ordinary rice varieties and create significant damage in the farms. The spread of gene pollution can be controlled by preventing either natural hybridization or the multiplication of seeds having undesirable genes. Gene pollution will not spread if the hybrid plants that integrate the undesirable genes do not produce progeny seeds. When new cultivars of rice are rised, the prevention of the spread of gene pollution should become a breeding objective. To prevent it, F1 weakness or F1 lethal genes could be used in such a breeding program.

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