To confirm the excellence in productivity of the stored seeds of wheat and two-rowed barley, we examined the growth characters and productivity of the plants developed from the seeds stored at 5★ and 40% relative humidity for various periods but showed a 80% or higher germination percentage, in comparison with those of newly harvested seeds (new seeds). The cultivars of stored seeds were identified by the random amplified polymorphic DNA (RAPD) method. There were no differences in the morphological characters of the seedlings 3 months after emergence between the new seeds and the old seeds (stored for 2 years and 5 months) or the very old seeds (stored for 10 years and 5 months or 16 years and 5 months). On the other hand, there was a positive correlation between the top dry weight at 3 months after emergence and 1, 000-grain weight of the seed. In the plants from the old seeds, no significant differences from those from new seeds were observed either in the mean heading date, maturing date, culm lengths, ear length, yield components, grain yield or inspection-grade. On the other hand, in the plants from the very old seeds, the mean heading date, maturing date, culm lengths, yield components and grain yield were significantly different from those in the new seeds in some cultivars. The results of RAPD analysis showed that the band pattern of the very old seeds was the same as that of the new seed in each cultivar. We concluded that the seeds of wheat and two-rowed barley stored for 2 years and 5 months with a germination percentage of higher than 80% are practically useful, showing normal growth characters and productivity. However, it should be noted that some cultivars had inferior grain yield after the seed storage for over 10 years.
The msm1 and msm2 cytoplasms cause male sterility in barley. In order to clarify whether these cytoplasms can be used for hybrid seed production in Japan, we investigated the fertility restoration under environmental conditions in Japan using alloplasmic lines and an isogenic line. Fertility of barley lines containing msm1 and msm2 was completely restored by the restorer gene Rfm1a. The effect of cytoplasm on malting quality was also investigated, but no significant difference in making quality was observed between lines possessing msm1, msm2, and original cytoplasms. Making quality also did not differ between Rfm1a/Rfm1a and Rfm1a/rfm1a genotypes, suggesting that Rfm1a and its flanking genes are not associated with heterosis for malting quality. Possibilities of hybrid barley breeding using these male sterile cytoplasms are discussed.
A rice husk restricts the grain development physically. We examined the correlation of the total husk volume on a panicle, a parameter of yield capacity, with the nitrogen concentration (per dry weight) and the dry weight of the above-ground part of the plant, using single-stem-trained japonica rice (cv. Nipponbare) plants. The growth of rice plants was regulated by shading at two levels and nitrogen application at three levels from about 40 days before the heading (about 10 days before the panicle initiation). The number of spikelets per dry weight of the above-ground part of the plant at the end of the spikelet differentiation stage was linearly correlated with the nitrogen concentration at that time. The ratio of the spikelet dry weight at heading to the dry weight of the above-ground part of the plant at the end of the spikelet differentiation stage increased as the nitrogen concentration increased at a low nitrogen concentration, but the increase of the ratio slowed down at a nitrogen concentration of 2%. Decrease in dry weight of the spikelet resulted in a decrease of lemma size. Therefore, the ratio of the total husk volume on a panicle to the plant dry weight at the end of spikelet differentiation stage also increased as the nitrogen concentration increased at a low nitrogen concentration, but the increase stopped at a nitrogen concentration of 2% in contrast to the ratio of the spikelet number to the dry weight of the plant. These results suggest that, to increase the total husk volume on a panicle by nitrogen application, dry-matter production must be increased by the nitrogen application.
Generally F1 hybrids from crosses between japonica and indica rice show variable degrees of sterility. Previous studies revealed that among the indica rice, the Aus type has sexual affinity with japonica cultivars giving higher fertility in F1 hybrids. Therefore, we made an effort to obtain higher grain yield by producing F1 hybrids between japonica and Aus-type indica. A field experiment was conducted to investigate the heterosis in these F1 hybrids for dry matter accumulation, spikelet fertility, yield and yield attributes, to find cross combinations with higher grain yield, and examined the relationships of grain yield with some agronomic characters. F1 hybrids flowered earlier than their parent cultivars. Heterosis for dry matter accumulation was positive at the panicle initiation stage, at heading and at maturity. The average heterosis for number of panicles, grain and straw yield per plant, number of spikelets per panicle and 1000-grain weight was positive. A few F1 hybrids showed positive heterosis for number of filled grains per panicle, spikelet fertility and harvest index; but the average heterosis for these traits was negative. Among the yield components, a higher number of panicles per plant and higher number of spikelet per panicle contributed to higher grain yield in F1 hybrids. A significant and positive relationship existed between spikelet fertility and grain yield per plant. The higher grain yield was attributed to higher dry matter production rather than higher harvest index in F1 hybrids, although low spikelet fertility limited yield potential in some F1 hybrids.
Rice (Oryza sativa L.) seedlings were subjected to a 24-h anoxic stress after hypoxic pretreatment (H-PT) for evaluation of the hypoxic acclimation to anoxia tolerance in their coleoptiles. The elongation of the coleoptiles of the seedlings subjected to H-PT was greater than that of non-pretreated (N-PT) seedlings. During pretreatment periods, alcohol dehydrogenase (EC 22.214.171.124) and pyruvate decarboxylase (EC 126.96.36.199) activities in the H-PT coleoptiles became 5.3- and 3.6-fold greater than those in the N-PT coleoptiles, respectively. The average production rate of ethanol during the initial 6 h after the onset of the anoxia stress was 3.7 and 1.3 ★mol g-1 fresh weight h-1 for the H-PT and N-PT coleoptiles, respectively. Coleoptiles of the seedlings lost ATP rapidly under the anoxic stress; however, the decrease in ATP was much slower in the H-PT coleoptiles than in the N-PT coleoptiles. These results are consistent with the results found in roots of several plants, suggesting that the mechanism in hypoxic acclimation to anoxia implicated in their roots may act in the rice coleoptiles.
Soybean (Glycine max (L.) Merr. cv. Enrei) plants were grown in pots (1 5-L volume) placed in a greenhouse with ventilation. At the time when the first flower opened, pots were transferred to growth chambers with natural lighting under day temperature of 30★ and night temperatures of 20, 25 or 30★. The numbers of flowers opened and pods set each day were recorded and the seed yield and yield components were investigated after harvest. The increase in night temperature decreased the seed size and increased the number of flowers and pods. As a result, the seed weight per plant was unaffected by night temperature. However, high night temperatures increased the number of flowers on the secondary and tertiary racemes. These flowers opened after the 18th day of the flowering period and showed a high rate of pod setting. These results suggest that a high night temperature stimulated flower opening and pod setting in the secondary and tertiary racemes. The increases in the numbers of flowers and pods could serve to moderate the reduction of seed yield caused by a high night temperature.
Introduction of the long-coleoptile trait in European varieties into Japanese elite varieties may improve seedling establishment and yield stability of the rice in the direct-seeding cultivation in cool climates. Some European varieties have long coleoptiles but they also have undesirable traits such as low yielding ability and bad grain appearance, which makes it difficult to improve coleoptile length in a rice breeding programs in Japan. To overcome this difficulty, we introduced the long-coleoptile trait of Arroz da Terra (Portuguese variety with long coleoptile) into Kitaibuki Uapanese elite variety for direct seeding cultivation) by backcrossing. Furthermore, we confirmed the effectiveness of introducing the long-coleoptile trait for the selection of lines with stable seedling establishment. The coleoptile length of Satsukei00019, a near isogenic line of Kitaibuki for the long-coleoptile trait, was about twice as long as that of Kitaibuki. The seedling establishment rate of Satsukei00019 was about 20% higher than that of Kitaibuki in the direct seeding cultivation in submerged fields. Eating quality, heading date and yield of Satsukei00019 were similar to those of Kitaibuki but 1, 000 grain weight of Satsukei00019 was larger. Therefore, the efficacy of backcross breeding to introduce the long-coleoptile trait of European varieties into Japanese elite varieties was confirmed. From these results, we concluded that the selection based on a longer coleoptile length improved seedling establishment in submerged fields in cool climates which can contribute to stable production of direct seeded rice.
Cotton (Gossypium hirsutum L.) and soybean (Glycine max (L.) Merr.) cultivars were grown under arid (Urumqi, Xinjiang, China) and humid (Matsudo, Chiba, Japan) conditions to analyze their abilities to adapt to arid conditions in terms of transpiration, leaf movement and leaf temperature. Under the arid condition, the leaf temperature of the cotton cultivars was higher than that of the soybean cultivar and the air temperature. There was no significant difference in leaf temperature among the cotton and soybean cultivars under the humid condition. The flow rate of stem sap in the cotton cultivars under the arid condition was always higher than that in the soybean cultivar, and was largely affected by vapor pressure deficit (VPD). Under the humid condition, however, the flow rates of stem sap were lower in the cotton cultivars than in the soybean cultivars. These results indicate that cotton can avoid heat stress by the high transpiring ability possibly supported by well-developed root systems, which leads to higher drought resistance under the arid condition. Soybean would adapt to arid conditions by the combination of paraheliotropic leaf movement and reduced transpiration.
Wild plants experience more severe abiotic stresses such as heat, cold, drought and salinity than crop plants do under natural environments and have developed more particular adaptation mechanisms. In order to understand those mechanisms for thermotolerance, we carried out a large scale screening of heat-stress inducible genes by differential display using 480 species of randomly amplified polymorphic DNA (RAPD) primers from the leaves of a semiarid plant (Aneurolepidium chinense (Trin.) kitag), which can grow vigorously under high temperature, drought and salinity conditions. A comparative analysis of gene expression between control and stress conditions led to the detection of 91 cDNA clones from heat-stressed plants. DNA sequence analysis and database searching revealed that 21 cDNA clones induced by heat stress have homology to known proteins. On the other hand, triple as many (75% of the total isolated clones) had homology to either putative or unknown proteins. Identified genes included those encoding proteins involved in signal transduction (PIP5kinase, receptor protein kinase, etc.), heat shock proteins, protein synthesis, and other enzymes related to abiotic stress. The stress induction in most of the candidates were confirmed at the transcriptional level, but some encoding signal transduction kinases could not be detected by Northern blot analysis. It showed that differential display is a powerful tool for cloning cDNAs induced by heat stress and these results thus obtained are useful for understanding the plant thermotolerance mechanism.
One hundred and eighty-two Zoysia spp. individuals (Z. matrella and Z. sinica) collected from the coast around Taiwan and Island Penghu were used as materials. They were transplanted to Taichung, and three to four months after transplanting, the zymograms of esterase and acid phosphatase were determined. There were 26 bands and 108 patterns in the esterase zymogram, and 9 bands and 12 patterns in the acid phosphatase zymogram. In the dendrogram based on the Euclidean distance analysis, the clones collected from the northern part of the east coast (EN, mainly consisting of limestone) had a longer distance to those from the other five regions. The distances between the clones from these five regions were shorter, in spite of the fact that the geographical distribution of Z. matrella and Z. sinica is different in these regions, probably due to the high ability of Zoysia spp. to hybridize interspecifically. Moreover, the clones from the EN region showed a lower diversity in both isozyme patterns and showed a lower adaptation to salinity due to the protection by calcium. It is concluded that the genetic variation of Zoysia in Taiwan as examined by isozyme analysis is more related to the specific adaptation to environmental factors in the habitats than to the taxonomic status.
We examined the genetic variation in the callus performance of the Al-tolerant and Al-susceptible genotypes of sorghum (Sorghum bicolor L.) on Al-containing medium. Addition of Al to the medium with a low pH, low Ca and low phosphate resulted in a severe decrease in the percentage of callus formation (CF) in both Al-tolerant and Al-susceptible genotypes. However, the percentage of callus formation in the explants from Al-tolerant genotypes was higher than that from susceptible genotypes on Al-containing medium. The genotypic difference in the relative growth of calli on Al-containing medium and in the suppression of callus formation by Al was in agreement with that in the hematoxylin staining score. Al might have been considered as a limiting factor that affected the callus growth. There was a significant correlation (r = -0.664*) between the percent relative suppression of callus formation by Al and the percentage of callus formation on Al-containing medium. The callus growth in fresh weight and size on Al -containing medium relative to that on Al-free medium (relative growth on Al-containing medium) was greater in Al-tolerant genotypes than in the other genotypes. The relative growth of callus in fresh weight and size on Al-containing medium significantly correlated (r = -0.820** and r = -0.956**, respectively) with the percent relative suppression of callus formation by Al. The tissue culture is considered to be a useful tool for selecting Al-tolerant haploids at the callus stage.
Quantifying dry matter partitioning into individual organs of plants is a key component for simulating crop growth and yield formation. This study was undertaken to develop a dynamic module of biomass partitioning over the entire duration of growth in wheat. The partitioning fraction of shoot or root was defined as the fraction of its dry weight in plant biomass, and partitioning fraction of green leaf, stem or ear as the fraction of its dry weight in shoot mass of wheat. The functional relationships of the partitioning fraction with physiological development time for the entire growth period were established, in which harvest index (HI) regulated partitioning fraction of ear to shoot biomass as a genetic parameter. The dry weight of individual organ was the product of the respective partitioning fraction and plant weight or shoot weight. Test of the model with the field experiment data sets involving different sowing dates, plant densities and nitrogen fertilization strategies indicated a good agreement between the predicted and observed values.
The response of microarthropod populations to different combinations of conservational agricultural practices was investigated in two field experiments. In the first experiment, cropping systems with combinations of tillage (conventional or reduced), biocide application (conventional or reduced), and fertilization (chemical or cattle manure compost) were compared. In the second experiment, five treatments including four fallow managements that received different levels of tillage, biocide, and organic matter input from vegetation were compared. The springtail (Collembola) population was higher with less tillage, less biocide application, and more organic matter input in both experiments, and these effects were additive; there was no specific combination of practices that has an interacting effect. The mite (Acari) population was also higher under most conservational treatments, and a significant interaction effect between tillage and organic matter application was found. A large increase in the Acari population under the combination of reduced tillage and higher organic matter input suggested that beneficial effects of these practices on the Acari community could be increased by integrating these practices. There was no significant correlation between the microarthropod populations and plant cover or soil chemical/physical properties measured. Slight changes in soil environments caused by agricultural practices may affect microarthropod communities substantially even before the changes in soil properties become detectable.