Microsatellite markers for population studies of the rice blast fungus,Magnaporthe grisea

We developed nine new microsatellite markers for rice blast (Magnaporthe grisea) population studies. These markers were used in addition to nine microsatellite markers previously developed by our group for mapping purpose. Altogether, the 18 markers were used in multiplex PCR (polymerase chain reaction) to characterize six populations from different geographical origins. The average number of alleles per locus across populations ranged from 1.2 to 7 and the total number of alleles detected from 2 to 19. Based on this large range of polymorphism, this set of markers is expected to be useful for different kind of population studies at different geographical scales.     

The Structure of Detoxin D1

The structure of detoxin D₁, one of the main active principles of detoxio complex, has been established on the basis of the degradative studies and spectral evidences as depicted in formula (I).

Detoxin D₁ has been demonstrated to belong to a new class of the depsipeptide contained an amino acid designated detoxinine which was newly isolated as a natural product.     

“绿色革命”新进展:赤霉素与氮营养双重调控的表观修饰助力水稻高产高效育种

以半矮秆育种为代表的“绿色革命”极大地提高了作物产量,但也带来氮营养利用效率降低的严重问题。“绿色革命”主要基于调控赤霉素的代谢和信号转导而实现。前期的研究发现,赤霉素信号转导关键因子DELLA蛋白通过调控GRF4而负调控氮素的吸收利用,为半矮秆品系氮利用效率低的问题提供了解决方案。最近的一项研究进一步揭示了GA信号途径与氮响应交叉互作的新机制。该研究发现水稻(Oryza sativa)NGR5是氮素调控分蘖数目的一个关键基因,其表达受氮诱导。通过招募PRC2,NGR5对D14和OsSPL14等分蘖抑制基因所在位点进行H3K27me3甲基化修饰,从而抑制其表达。而在半矮秆背景下超表达NGR5可以提高低氮水平下的水稻产量。NGR5同时也被发现为赤霉素受体GID1的一个新靶标,受到其负调控。该研究发现了调控赤霉素信号通路的新机制,并对高产高效的新一代“绿色革命”育种实践具有重要启示。     

Silicon induces phytochelatin and ROS scavengers facilitating cadmium detoxification in rice

• Cadmium (Cd) is detrimental to crops and the environment. This work examines the natural mechanisms underlying silicon‐ (Si‐)directed Cd detoxification in rice plants.
• The addition of Si to plants under Cd stress caused significant improvements in morphological parameters, chlorophyll score, F_v/F_m and total soluble protein concentration compared to controls, confirming that Si is able to ameliorate Cd‐induced damage in rice plants. This morpho‐physiological evidence was correlated with decreased cell death and electrolyte leakage after Si application.
• The results showed no critical changes in root Cd concentration, while shoot Cd decreased significantly after Si supplementation in comparison with Cd‐stressed rice. Additionally, expression of Cd transporters (OsNRAMP5 and OsHMA2) was significantly down‐regulated while the concentration of phytochelatin, cysteine and glutathione, together with expression of OsPCS1 (phytochelatin synthase) in roots of Cd‐stressed rice was significantly induced when subjected to Si treatment. This confirms that the alleviation of Cd stress is not only limited to the down‐regulation of Cd transporters but also closely related to the phytochelatin‐driven vacuolar storage of Cd in rice roots.
• The enzymatic analysis further revealed the role of SOD and GR enzymes in protecting rice plants from Cd‐induced oxidative harm. These findings suggest a mechanistic basis in rice plants for Si‐mediated mitigation of Cd stress.

     

Rice straw decomposition in rice-field soil

Rice straw, buried in a rice-field during the dry season decomposed at a rate of 0.0075 day-1. Seventy five percent of the biomass, 70 percent carbon, 50 percent nitrogen and 30 percent phosphorus remained after 139 days of decomposition. Rice straw decomposition furnished 33% N and 8% P of the total nitrogen and phosphorus provided by man.     

Relationships between rhizoplane and rhizosphere bacteria and verticillium wilt resistance in potato

Six cultivars and breeding lines of potato (Solanum tuberosum) differing in susceptibility to verticillium wilt caused by Verticillium dahliae were studied with respect to quantitative and qualitative differences in the bacterial flora of their soil and rhizosphere-rhizoplane. Although, no association was observed between the types of bacteria that inhabited the soil or roots of wilt resistant and susceptible cultivars, quantitative differences were evident. These differences provide the first direct evidence that potato genotypes can influence bacterial populations. Bacterial populations were 9–25-fold higher on roots than in the adjacent soil. As the plants aged, the total number of rootcolonizing bacteria increased between 15 and 245%. Pseudomonas spp. were the most abundant microbes in the soil and rhizosphere-rhizoplane. The bacteria antagonistic to V. dahliae in vitro were identified as members of the genera Bacillus, Pseudomonas, Flavobacterium, and Gluconobacter. A statistically significant trend was evident toward the association of antagonistic bacteria with the more resistant potato cultivars.     

Changes in DTPA-iron and management of iron chlorosis in rice nurseries

Summary On a Typic Ustochrept soil incorporation of 10 tons/ha of a green manure plus submergence for 10 days followed by raising upland nursery checked iron chlorosis. In contrast, presubmergence with and without FYM and iron sulfate or pyrite were a failure. Nor weekly sprays with 3.0% iron sulfate were found very effective. The success of green manure plus submergence was associated with the mobilization of soil iron as a result of intense reduction and its subsequent retention in available form at a sufficient high level during the growth of upland nursery.     

Soil and plant tests for available sulfur in wetland rice soils

Summary Soil tests, plant performance, and plant tissue analyses were used to study the availability of sulfur to wetland rice in 30 Philippine soils. The critical concentrations of available sulfur by the calcium phosphate, lithium chloride, ammonium acetate, and hydrochloric acid extractions were 9, 25, 30, and 5 mg/kg, respectively. The critical total sulfur limits were 0.11% in the shoot at maximum tillering 0.055% in the straw at maturity, and 0.065% in the grain. The critical N:S ratio was 15 in the shoot at maximum tillering, 14 in the straw at maturity, and 26 in the grain. The critical sulfate-sulfur limit was 150 mg/kg in the shoot at maximum tillering and 100 mg/kg in the straw at maturity. The critical sulfate-sulfur/total sulfur percentage ratio was 15% in the shoot at maximum tillering and the straw at maturity. Plant performance, judged by appearance and yield of dry matter, straw, and grain, was generally poorer in the sulfur deficient soils than in the other soils. Although the calcium phosphate and ammonium acetate methods gave a better correlation between plant performance and available sulfur than the others, all four methods separated sulfur-deficient soils from non-deficient ones. The hydrochloric acid method merits further study because it is simple and versatile.     

Alleviation of sodicity stress on rice genotypes by Phosphorus fertilization

Rice seedlings transplanted into sodic soil are exposed to an excess of potentially toxic ions as well as nutritional imbalance, both of which adversely affect their growth and yield. The present study was aimed to investigate the beneficial effects of fertilization with phosphorus and potassium on the plants at varying sodicity levels and also the response of genotypes with known variability in their tolerance to sodicity. In pot-house experiments during two seasons, the alleviating effects of P and K fertilization on three rice genotypes were examined at four sodicity levels. Seedlings of CSR13 and Jaya (both moderately tolerant to sodicity), died by 25–35 days after transplanting in sodic soils of pH 9.7–9.9 where Olsen's P was 12.5 and 14.8 kg/ha, respectively. However, there was no problem of survival or growth in these soils when Olsen's P was 17.6 and 20.8 kg/ha. Depletion in P from 12.0 kg to 10 kg resulted in some mortality of the seedlings even at pH 9.1. Sodicity tolerant genotype CSR10, did show some survival and growth even at pH 9.9 with Olsen's P at 14.8 kg/ha (without P fertilization) which suggests that differences in tolerance to sodicity which exist at genotypic level are not masked by low P. None of the three genotypes showed any survival problem at pH 8.0 and 8.1 with Olsen's P at 8.5 and 8.7 kg/ha, respectively. Seedlings in P fertilized sodic soils not only produced significantly more new roots but also higher root biomass than those in unfertilized sodic soils and these roots seem to have some control on Na uptake as reflected by low Na concentration in the shoots. Thus, P fertilization not only improved P and K status of plants but also reduced the concentration of potentially toxic Na ions in shoots, resulting in better survival, growth and yield. Although fertilization with K alone did improve shoot K content, it had no significant effect on reducing Na. So the mortality of the seedlings or grain yield in K fertilized sodic soils was as good as in control and this could be explained on the basis of lack of any significant difference in Na concentrations in shoots between these two treatments.