The identification of stable quantitative trait locus (QTL) for yield-related traits and tightly linked molecular markers is important for improving wheat grain yield. In the present study, six yield-related traits in a recombinant inbred line (RIL) population derived from the Zhongmai 578/Jimai 22 cross were phenotyped in five environments. The parents and 262 RILs were genotyped using the wheat 50K single nucleotide polymorphism (SNP) array. A high-density genetic map was constructed with 1 501 non-redundant bin markers, spanning 2 384.95 cM. Fifty-three QTLs for six yield-related traits were mapped on chromosomes 1D (2), 2A (9), 2B (6), 2D, 3A (2), 3B (2), 4A (5), 4D, 5B (8), 5D (2), 7A (7), 7B (3) and 7D (5), which explained 2.7–25.5% of the phenotypic variances. Among the 53 QTLs, 23 were detected in at least three environments, including seven for thousand-kernel weight (TKW), four for kernel length (KL), four for kernel width (KW), three for average grain filling rate (GFR), one for kernel number per spike (KNS) and four for plant height (PH). The stable QTLs QKl.caas-2A.1, QKl.caas-7D, QKw.caas-7D, QGfr.caas-2B.1, QGfr.caas-4A, QGfr.caas-7A and QPh. caas-2A.1 are likely to be new loci. Six QTL-rich regions on 2A, 2B, 4A, 5B, 7A and 7D, showed pleiotropic effects on various yield traits. TaSus2-2B and WAPO-A1 are potential candidate genes for the pleiotropic regions on 2B and 7A, respectively. The pleiotropic QTL on 7D for TKW, KL, KW and PH was verified in a natural population. The results of this study enrich our knowledge of the genetic basis underlying yield-related traits and provide molecular markers for high-yield wheat breeding.

Artemisia annua is an important preferred host of the mirid bug Apolygus lucorum in autumn.  Volatiles emitted from A. annua attract A. lucorum.  Volatile artemisinic acid of A. annua is a precursor of artemisinin that has been widely investigated in the Chinese herbal medicine field.  However, little is known at this point about the biological roles of artemisinic acid in regulating the behavioral trends of A. lucorum.  In this study, we collected volatiles from A. annua at the seedling stage by using headspace solid phase microextraction (HS-SPME).  Gas chromatography-mass spectrometry (GC-MS) analysis showed that approximately 11.03±6.00 and 238.25±121.67 ng h^–1 artemisinic acid were detected in volatile samples and milled samples, respectively.  Subsequently, a key gene for artemisinic acid synthesis, the cytochrome P450 gene cyp71av1, was expressed in engineered Saccharomyces cerevisiae to catalyze the production of artemisinic acid.  After the addition of exogenous artemisinic alcohol or artemisinic aldehyde, artemisinic acid was identified as the product of the expressed gene.  In electroantennogram (EAG) recordings, 3-day-old adult A. lucorum showed significant electrophysiological responses to artemisinic alcohol, artemisinic aldehyde and artemisinic acid.  Furthermore, 3-day-old female bugs were significantly attracted by artemisinic acid and artemisinic alcohol at a concentration of 10 mmol L^–1, whereas 3-day-old male bugs were attracted significantly by 10 mmol L^–1 artemisinic acid and artemisinic aldehyde.  We propose that artemisinic acid and its precursors could be used as potential attractant components for the design of novel integrated pest management strategies to control A. lucorum.

Auxin regulates cell division and elongation of the primordial cells through its concentration and then shaped the plant architecture.  Cell division and elongation form the internode of soybean and result in different plant heights and lodging resistance.  Yet the mechanisms behind are unclear in soybean.  To elucidate the mechanism of the concentration difference of auxin related to stem development in soybean, samples of apical shoot, elongation zone, and mature zone from the developing stems of soybean seedlings, Charleston, were harvested and measured for auxin concentration distributions and metabolites to identify the common underlying mechanisms responsible for concentration difference of auxin.  Distribution of indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and methylindole-3-acetic acid (Me-IAA) were determined and auxin concentration distributions were found to have a complex regulation mechanism.  The concentrations of IAA and Me-IAA in apical shoot were significantly different between elongation zone and mature zone resulting in an IAA gradient.  Tryptophan dependent pathway from tryptamine directly to IAA or through indole-3-acetonitrile to IAA and from indole-3-propionic acid (IPA) to IAA were three primary IAA synthesis pathways.  Moreover, some plant metabolites from flavonoid and phenylpropanoid synthesis pathways showed similar or reverse gradient and should involve in auxin homeostasis and concentration difference.  All the data give the first insight in the concentration difference and homeostasis of auxin in soybean seedlings and facilitate a deeper understanding of the molecular mechanism of stem development and growth.  The gathered information also helps to elucidate how plant height is formed in soybean and what strategy should be adopted to regulate the lodging resistance in soybean.

Abundant genetic diversity and rational population structure of germplasm benefit crop breeding greatly. To investigate genetic variation among geographically diverse set of japonica germplasm, we analyzed 233 japonica rice cultivars collected from Liaoning, Jilin and Heilongjiang provinces of China, which were released from 1970 to 2011 by using 62 simple sequence repeat (SSR) markers and 8 functional gene tags related to yield. A total of 195 alleles (Na) were detected with an average of 3.61 per locus, indicating a low level of genetic diversity level among all individuals. The genetic diversity of the cultivars from Jilin Province was the highest among the three geographic distribution zones. Moreover, the genetic diversity was increased slightly with the released period of cultivars from 1970 to 2011. The analysis of molecular variance (AMOVA) revealed that genetic differentiation was more diverse within the populations than that among the populations. The neighbor-joining (NJ) tree indicated that cultivar clusters based on geographic distribution represented three independent groups, among which the cluster of cultivars from Heilongjiang is distinctly different to the cluster of cultivars from Liaoning. For the examined functional genes, two or three allelic variations for each were detected, except for IPA1 and GW2, and most of elite genes had been introgressed in modern japonica rice varieties. These results provide a valuable evaluation for genetic backgrounds of current japonica rice and will be used directly for japonica rice breeding in future.

Phosphorus (P) is one of the three primary macronutrients that are required in large amounts for plant growth and development. To better understand molecular mechanism of maize and identify relevant genes in response to phosphorus deficiency, we used Solexa/Illumina’s digital gene expression (DGE) technology to investigate six genome-wide expression profiles of seedling roots of the low-P tolerant maize inbred line 178. DGE studies were conducted at 6, 24 and 72 h under both phosphorus deficient and sufficient conditions. Approximately 3.93 million raw reads for each sample were sequenced and 6 816 genes exhibited significant levels of differential expressions in at least one of three time points in response to P starvation. The number of genes with increased expression increased over time from 6 to 24 h, whereas genes with decreased expression were more abundant at 72 h, suggesting a gradual response process for P deficiency at different stages. Gene annotations illustrated that most of differentially expressed genes (DEGs) are involved in different cellular and molecular processes such as environmental adaptation and carbohydrate metabolism. The expression of some known genes identified in other plants, such as those involved in root architecture, P metabolism and transport were found to be altered at least two folds, indicating that the mechanisms of molecular and morphological adaptation to P starvation are conserved in plants. This study provides insight into the general molecular mechanisms underlying plant adaptation to low-P stress and thus may facilitate molecular breeding for improving P utilization in maize.

Large grain is a favorable trait for appearance quality and large sink potential in wheat breeding.  A stable QTL QGl.caas-5BS for grain length was previously identified in a recombinant inbred line population from the cross of Zhongmai 871 (ZM871) and its sister line Zhongmai 895 (ZM895).  Here, a BC₁F₆ residual heterozygous line was selected from the cross of ZM871/ZM895//ZM871 population, and six heterozygous recombinant plants were identified in the BC₁F₇ population from self-pollination of the heterozygous line.  QGl.caas-5BS was delimited into an interval of approximately 2.2 Mb flanked by markers Kasp_5B33 and Kasp_5B2 (25.3-27.5 Mb) through phenotyping and genotyping the secondary mapping populations derived from these heterozygous recombinant plants.  Five genes were predicted as candidates of QGl.caas-5BS based on sequence polymorphism and differential expression analyses.  Further mutation analysis showed that TraesCS5B02G026800 is likely the causal gene of QGl.caas-5BS.  A gene-specific marker Kasp_5B_Gl for TraesCS5B02G026800 was developed, and a significant genetic effect of QGl.caas-5BS on grain length was identified in a validation population including 166 cultivars using the marker.  These findings lay a good foundation for map-based cloning of QGl.caas-5BS and provide a breeding-applicable marker for the improvement of grain length in wheat.