Rwt4 , a wheat gene for resistance to Avena isolates of Magnaporthe oryzae , functions as a gene for resistance to Panicum isolates in Japan

Rwt4 (synonym of Rmg1), a temperature-insensitive gene for resistance to Avena isolates of Magnaporthe oryzae, was identified in wheat cultivar Norin 4 in a seedling assay. The significance of Rwt4 was evaluated using flag leaves of wheat cultivars. At high temperature, Norin 4 was completely resistant to Avena isolate Br58, while Chinese Spring, a noncarrier of Rwt4, was susceptible. Genetic analysis of F₂ plants derived from Norin 4 × Chinese Spring indicated that the resistance of flag leaves of Norin 4 to the Avena isolate is conditioned by a single major gene. Segregation analysis of F₃ seedlings derived from the F₂ plants showed that the major gene is actually Rwt4. These results suggest that Rwt4 is effective against Avena isolates throughout the growth stages. Furthermore, screening of Pyricularia isolates from various hosts suggested that Panicum isolates are possible carriers of the corresponding avirulence gene, PWT4. Segregation analyses of F₂ and F₃ seedlings showed that Panicum isolates actually carry PWT4, and, therefore, that Rwt4 is also effective against Panicum isolates. On the other hand, none of the Oryza, Setaria, Triticum, and Lolium isolates tested was a carrier of PWT4. The significance of this finding is discussed from the viewpoint of epidemics of blast disease on wheat.     

Winter hardiness in Turkish populations of cocksfoot,Dactylis glomerata L.

Summary Over a six-year period, Turkish populations of cocksfoot were investigated in the field at Sapporo, Japan, as to winter hardiness. After the first winter, only populations from the mild Marmara, Aegean and Mediterranean regions were badly damaged. As the differential plant survival among geographical groups widened with the elapsing of years, we were able to rank the groups in descending order of relative hardiness from Eastern Anatolia, through the Black Sea, Central Plateau, Marmara and Aegean regions, to the Mediterranean region. This order was maintained throughout the experimental period.Winter temperatures prevailing in the locality of origin was the most important determinant of winter survival of the populations. The growth pattern in autumn and whether plants continued to grow through the winter or were enforced to winter dormancy, were related to differential survival between maritime and mountainous populations. On the other hand, this simple relationship is complicated by introgression. The subspecies distribution in the coastal region is related to a higher level of survival in the populations from the Black Sea region, where the continental type of cocksfoot occurs, than in the populations from the other maritime regions, where introgression has occurred from Daetylis glomerata subsp. hispanica with poor winter hardiness.Present address: Tropical Agriculture Research Center, Okinawa Branch, Ishigaki 907-01, Japan.     

Measurement of diurnal changes in stem and branch diameters using strain gauges

The applicability of a strain gauge for monitoring the diurnal changes of tree stem diameters and the differences in diurnal shrinkages between a stem and branches were investigated. Estimates of stem diameter changes obtained by a strain gauge were compared with changes obtained by a differential transformer. Patterns of strain changes obtained by a strain gauge were remarkably similar to the changes in the tree trunk diameter. This results demonstrated that a strain gauge is an effective technique for examining the behavior of changes in tree trunk diameter. Diurnal changes of diameter at various parts of the a tree were also measured with the help of several strain gauges. Diurnal strain changes of a stem and branches showed similar patterns of shrinkage during the day and swelling at night. However, the precise times at which the branches had their maximum and minimum strains differed from those observed in the stem, and the maximum rates of the strain changes lagged behind the stems in a day. These results lead us to believe that there is a time lag in the supply of water, which is required for compensating the water deficit between the stem and its branches. A part of this paper was presented at the 105th Annual Meeting of Japanese Forestry Society (1994).     

Fractionation of humic acid by organic solvents

TJURIN (1) had proposed the use of organic solvent to fractionate humus. In his method, he extracted soils with benzene-alcohol (1 : 1) mixture in the SOXHLET's apparatus. The extract was dried at 80°C and weighed.     

Deformation of humic acid by acid treatment

In our previous report (1) we had proposed the method to fractionate humic acid into three parts using organic solvents, and had advocated the new theory on the process of humification in volcanic ash soils from the results of the fractionation.     

Method for assessing resistance of wheat to speckled snow mold (<Emphasis Type="Italic">Typhula ishikariensis</Emphasis>) under controlled conditions

A method was developed for assessing the resistance of wheat to speckled snow mold (Typhula ishikariensis) under controlled conditions in all steps. We modified the method of Nakajima and Abe and estimated the optimum conditions consisting of 2 weeks each for prehardening and hardening, 6 weeks for incubation at 8°C, and 2 weeks for regrowth in a greenhouse for screening resistance. The present method reduced the experimental period to 12 weeks and facilitated repeated experiments throughout the year.     

Relation between cell‐bound exopolysaccharide production via plasmid‐encoded genes and rugose colony morphology in the probiotic Lactobacillus brevis KB290

The probiotic Lactobacillus brevis KB290 is a natural producer of cell‐bound exopolysaccharide (EPS), and the plasmid‐encoded glycosyltransferase genes are responsible for this EPS production. KB290 forms unique rugose colonies inside an agar medium; this characteristic is useful for detecting and enumerating KB290 in the gut or feces. However, the genetic elements associated with this morphology remain unclear. Here, we aimed to investigate the relation between the plasmid eps genes and rugose colony morphology in KB290. The plasmid‐cured mutants formed smooth colonies, and the rugose colony morphology was restored after complementation with the eps genes. The eps genes were successfully cloned and expressed in other L. brevis and L. plantarum strains. In these transformant strains, the presence of the EPS, consisting of glucose and N‐acetylglucosamine, correlated with rugose colonies, indicating that EPS is responsible for rugose colony formation. To the best of our knowledge, this is the first report identifying the genetic factors influencing rugose colonies in Lactobacillus strains. This rugose colony formation may serve as a useful selective marker for KB290 in routine laboratory and research settings and can be used to detect the spontaneous loss of plasmids in this strain.     

Reduction in aggressiveness among hybrids between host-specific pathotypes of Magnaporthe oryzae is caused by reduced ability to overcome adult resistance at the level of penetration

A genetic cross between a Triticum isolate (pathogenic on wheat) and a Setaria isolate (pathogenic on foxtail millet) of Magnaporthe oryzae yielded several F₁ cultures that were virulent on both wheat and foxtail millet at the primary leaf stage. To estimate whether these cultures survive in nature, they were sprayed onto 1-, 2-, and 3-week-old wheat and foxtail millet. As the age of the inoculated plants increased, the lesion number and size were greatly reduced. The F₁ cultures were almost nonpathogenic on both wheat and foxtail millet at the 3-week-old stage. Cytological analysis revealed that the low pathogenicity of the F₁ cultures on older plants was primarily associated with a reduced ability to penetrate the cuticle. When placed on wounded leaf surfaces, the F₁ cultures produced large lesions on 4-week-old wheat and foxtail millet. These results indicate that hybridization between species-specific pathotypes results in a reduction of aggressiveness. We therefore suggest that, even if such hybrids were produced in nature, they might not survive in the natural environment.     

High sensitivity of thymocytes of LEC strain rats to induction of apoptosis by X-irradiation

It is known that physical disruption of cell contacts induces apoptosis of thymocytes. When thymocytes from LEC and WKAH rats were incubated in vitro at 37 degrees C for 0-6 hr and then the proportion of apoptotic cells was determined using a flow cytometer, it was found that the percentages of apoptotic thymocytes from both LEC and WKAH rats increased with incubation time and that the proportion of apoptotic cells from LEC rats was significantly higher than that from WKAH rats at each incubation time. The fact that cycloheximide, an inhibitor of protein synthesis, did not show significant inhibitory effects on induction of apoptosis of thymocytes indicates that induction of apoptosis during in vitro cultivation did not require de novo protein synthesis. When thymocytes from LEC and WKAH rats were X-irradiated in vitro at 4 and 8 Gy, the percentages of radiation-induced apoptotic cells increased with post-incubation time after X-irradiation in both LEC and WKAH rat thymocytes and the proportions of apoptotic cells from LEC rats were significantly higher than those from WKAH rat cells at 2 and 4 hr post-incubation after X-irradiation. When thymocytes from LEC and WKAH rats were X-irradiated in the presence of cycloheximide, the induction of apoptosis was substantially inhibited, indicating that radiation-induced apoptosis of thymocytes from LEC and WKAH rats required de novo protein synthesis. The present results showed high sensitivities of thymocytes of LEC rats to induction of apoptosis during in vitro cultivation and by X-irradiation.