Brassinosteroids (BRs) are a class of plant-specific steroidal hormones that play important roles in multiple biological processes. In this paper, a classic rice mutant gsor300084, showing erect leaves and semi-dwarf stature, was characterized. Morphological analysis in darkness showed that the mesocotyl of the gsor300084 mutant did not elongate when grown in darkness. Coleoptile elongation and root growth were less affected by the exogenous application of brassinolide (BL), the most active form of BR, in gsor300084 than in the wild-type rice variety Matsumae. Lamina joint bending analysis also showed that gsor300084 was less sensitive to exogenous BL than Matsumae. These results suggested that the gsor300084 mutant is defective in BR sensitivity. Map-based cloning indicated that gsor300084 is a novel allelic mutant of the DWARF61 (D61) gene, which encodes the putative BR receptor OsBRI1. A single-base mutation appears in the LRR domain of OsBRI1, changing the 444th amino acid from tryptophan (W) to arginine (R). Subcellular localization analysis suggested that both the wild-type and mutant OsBRI1 protein are localized at the cytoplasmic membrane. Structure modeling revealed that the W444R substitution may affect the perception of BRs by the LRR domain.

Common bean is an important but often a disease-susceptible legume crop of temperate, subtropical and tropical regions worldwide. The crop is affected by bacterial, fungal and viral pathogens. The strategy of resistance-gene homologue (RGH) cloning has proven to be an efficient tool for identifying markers and R (resistance) genes associated with resistances to diseases. Microsatellite or SSR markers can be identified by physical association with RGH clones on large-insert DNA clones such as bacterial artificial chromosomes (BACs). Our objectives in this work were to identify RGH-SSR in a BAC library from the Andean genotype G19833 and to test and map any polymorphic markers to identify associations with known positions of disease resistance genes. We developed a set of specific probes designed for clades of common bean RGH genes and then identified positive BAC clones and developed microsatellites from BACs having SSR loci in their end sequences. A total of 629 new RGH-SSRs were identified and named BMr (bean microsatellite RGH-associated markers). A subset of these markers was screened for detecting polymorphism in the genetic mapping population DOR364 × G19833. A genetic map was constructed with a total of 264 markers, among which were 80 RGH loci anchored to single-copy RFLP and SSR markers. Clusters of RGH-SSRs were observed on most of the linkage groups of common bean and in positions associated with R-genes and QTL. The use of these new markers to select for disease resistance is discussed.

The objective of this study was to investigate variation and trends in dough rheological properties and flour quality traits in 330 Chinese wheat varieties. The dough rheological properties of development time (DT), stability time (ST), and farinograph quality number (FQN) were evaluated, as well as the flour quality traits of protein (PC), wet gluten content (WGC), and sedimentation value (SV). The coefficients of variation of DT (40.5%), ST (58.1%), and FQN (42.4%) were higher than those of PC (9.1%), WGC (10.1%), and SV (15.3%). Normal distributions were observed for the flour quality indices but not for the rheological parameters. SV was strongly correlated with the three rheological parameters and accordingly might be used as a primary indicator for dough rheological property evaluation. Our results showed that there has been marked improvement in dough rheological properties for Chinese wheat varieties released since 1986, while flour quality has remained stable.

Nitrogen (N) is the most important fertiliser element determining the productivity of wheat. N nutrition is known to affect the level of stripe rust infection, with higher N associated with increased disease severity. Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a major yield-limiting disease of wheat in Australia. This paper describes experiments designed to investigate the agronomic response to the interaction of various levels of N application and stripe rust severity in wheat varieties differing in response. Experimental plots were established in crop seasons 2006 and 2007 on the Liverpool Plains of northern NSW, Australia. Yield, biomass, grain protein content (GPC) and harvest index (HI) data were recorded. Increased rates of N increased the severity of stripe rust during grain filling. N application also increased yield and GPC in all varieties in both years. Stripe rust reduced the yield of the rust-susceptible wheat varieties, and GPC and proportion of added N recovered in the grain were also reduced in one year but not the other. It was evident from our experiment that stripe rust caused yield loss accompanied by either no change or reduction in GPC, indicating that the total amount of N entering the grain was reduced by stripe rust. The effects of stripe rust on N yield are most likely associated with reduced uptake of N during grain filling.

Free air CO₂ enrichment (FACE) and nitrogen (N) have marked effects on rice root growth, and numerical simulation can explain these effects. To further define the effects of FACE on root growth of rice, an experiment was performed, using the hybrid indica cultivar Xianyou 63. The effects of increasing atmospheric CO₂ concentration [CO₂], 200 μmol mol^{− 1} higher than ambient, on the growth of rice adventitious roots were evaluated, with two levels of N: low (LN, 125 kg ha^{− 1}) and normal (NN, 250 kg ha^{− 1}). The results showed a significant increase in both adventitious root number (ARN) and adventitious root length (ARL) under FACE treatment. The application of nitrogen also increased ARN and ARL, but these increases were smaller than that under FACE treatment. On the basis of the FACE experiment, numerical models for rice adventitious root number and length were constructed with time as the driving factor. The models illustrated the dynamic development of rice adventitious root number and length after transplanting, regulated either by atmospheric [CO₂] or by N application. The simulation result was supported by statistical tests comparing experimental data from different years, and the model yields realistic predictions of root growth. These results suggest that the models have strong predictive potential under conditions of atmospheric [CO₂] rises in the future.

Foliar diseases are common in most maize-producing regions and have caused serious yield reduction in China. To evaluate genetic resistance of parental lines actively used in maize breeding programs to major foliar diseases, 152 maize inbred lines were tested against northern corn leaf blight (NCLB), southern corn leaf blight (SCLB), Curvularia leaf spot (CLS), gray leaf spot (GLS), common rust, and southern rust from 2003 to 2005. A small number of lines exhibited highly resistant reactions to common rust and southern rust, but none were highly resistant to NCLB, SCLB, CLS, and GLS. Although 53.3%, 40.8%, and 80.7% of lines were resistant to NCLB, SCLB, and common rust, the resistance in most lines was moderate. Resistance to CLS, GLS, and southern rust was rare in this collection of maize lines. Five lines, 313, Chang 7-2, Qi 319, Qi 318, and Shen 137, were resistant to five diseases tested. Lines belonging to heterotic subgroup PB exhibited better resistance to the foliar diseases than lines from other heterotic subgroups, such as BSSS, PA, Lancaster, LRC, and PA. The results will be of benefit to breeders for selecting lines in disease resistance breeding programs.

Switchgrass (Panicum virgatum L.) is a warm-season rhizomatous perennial grass that can tolerate diverse abiotic stresses while yielding relatively high biomass, and is considered a leading biofuel feedstock for marginal lands. Nitrogen (N) is crucial for the growth and development of switchgrass, and its tolerance to low N supply and high N use efficiency are very important for its production under poor conditions. The large-scale planting of switchgrass on marginal lands could be an effective approach to solving the problem of feedstock supply for biomass energy. This study used a hydroponic experiment to evaluate the effect of N deficiency on switchgrass seedlings. Three N treatments (0, 0.15, and 1.50 mmol L^{− 1} Hoagland's solution) and six cultivars were used, three of each ecotype (upland and lowland). The results showed that biomass, leaf area, root surface area, net photosynthesis, and total chlorophyll content significantly decreased under low N treatments compared with those in full strength Hoagland's nutrient solution. However, once established, all plants survived extreme N stress (0 mmol L^{− 1}) and, to some extent, were productive. Cultivar Kanlow performed best of the six cultivars under stress. Significant interactions between stress treatment and cultivars showed that breeding for cultivars with high yield and superior performance under N deficiency is warranted. The lowland outperformed the upland ecotypes under stress, suggesting that lowland cultivars may survive and be productive under a wider range of stress conditions. However, given the better adaptability of lowland ecotypes to hydroponic cultivation, further study is needed.

Improvement of yield in rice (Oryza sativa L.) is vital for ensuring food security in China. Both rice breeders and growers need an improved understanding of the relationship between yield and yield-related traits. New indica cultivars (53 in 2007 and 48 in 2008) were grown in Taoyuan, Yunnan province, to identify important components contributing to yield. Additionally, two standard indica rice cultivars with similar yield potentials, II You 107 (a large-panicle type) and Xieyou 107 (a heavy-panicle type), were planted in Taoyuan, Yunnan province and Nanjing, Jiangsu province, from 2006 to 2008 to evaluate the stability of yield and yield-related attributes. Growth duration (GD), leaf area index (LAI), panicles per m² (PN), and spikelets per m² (SM) were significantly and positively correlated with grain yield (GY) over all years. Sequential path analysis identified PN and panicle weight (PW) as important first-order traits that influenced grain yield. All direct effects were significant, as indicated by bootstrap analysis. Yield potential varied greatly across locations but not across years. Plant height (PH), days from heading to maturity (HM), and grain weight (GW) were stable traits that showed little variation across sites or years, whereas GD (mainly the pre-heading period, PHP) and PN varied significantly across locations. To achieve a yield of 15 t ha^{− 1}, a cultivar should have a PH of 110-125 cm, a long GD with HM of approximately 40 days, a PN of 300-400 m^{− 2}, and a GW of 29-31 mg.

Cytokinin oxidase/dehydrogenase (CKX; EC.1.5.99.12) regulates cytokinin (CK) level in plants and plays an essential role in CK regulatory processes. CKX proteins are encoded by a small gene family with a varying number of members in different plants. In spite of their physiological importance, systematic analyses of SiCKX genes in foxtail millet have not yet been examined. In this paper, we report the genome wide isolation and characterization of SiCKXs using bioinformatic methods. A total of 11 members of the family were identified in the foxtail millet genome. SiCKX genes were distributed in seven chromosomes (chromosome 1, 3, 4, 5, 6, 7, and 11). The coding sequences of all the SiCKX genes were disrupted by introns, with numbers varying from one to four. These genes expanded in the genome mainly due to segmental duplication events. Multiple alignment and motif display results showed that all SiCKX proteins share FAD- and CK-binding domains. Putative cis-elements involved in Ca^{2 +}-response, abiotic stress response, light and circadian rhythm regulation, disease resistance and seed development were present in the promoters of SiCKX genes. Expression data mining suggested that SiCKX genes have diverse expression patterns. Real-time PCR analysis indicated that all 11 SiCKX genes were up-regulated in embryos under 6-BA treatment, and some were NaCl or PEG inducible. Collectively, these results provide molecular insights into CKX research in plants.