Active optical sensors (AOSs) are used for in-season variable-rate application of nitrogen (N). The sensors measure crop reflectance expressed as vegetative indices (VIs). These are transformed into N recommendations during on-site calibration of AOSs—‘familiarising’ the sensors with the crop N status of the representative part of a field. The ‘drive-first’ method is often used by growers to calibrate AOSs. Due to large spatial variation of crop N status within fields, it is difficult to identify the most representative sample strip for AOS calibration. Seven site-years were used to evaluate the sensitivity of sensor-based N prescriptions for winter wheat (Triticum aestivum L.) to selection of sample strips for AOS calibration that fall into extreme, very low or very high values of 95th percentiles of amber normalised difference VI (NDVI) values. A Crop Circle ACS-210 sensor was used to collect canopy reflectance values, expressed as amber NDVI, at the beginning of wheat stem elongation. Our study showed that the sample-strip selection significantly affected sensor-based N prescriptions. The drive-first method may result in under- or over-applications of N and in lower N-use efficiency. One way to overcome this problem is to collect whole field NDVI values during pesticide application before sensor-based N application. The NDVI values from the entire field then can be used to choose the most representative sample strips for AOS calibration.

Continuous improvement of potential yield is one of the most important goals of wheat breeding. The introduction of synthetic hexaploid wheat (SHW) germplasm has broken the bottleneck in potential yield, taking wheat breeding in China’s Sichuan Basin to a new level. However, systematic research on the physiological basis of high-yielding, SHW-derived cultivars has lagged behind. In the present study, three SHW-derived, high-yielding cultivars and three typical, non-synthetic cultivars widely used in wheat production were chosen for a 5-year study. Post-anthesis canopy structure, rates of canopy apparent photosynthesis (CAP), attenuation during grain filling, dry matter partitioning and other physiological parameters were studied. The average yield of the SHW-derived cultivars was 9154 kg ha^–1, which was 13.5% higher than that of the non-synthetic cultivars. The increased yield was due to increased biomass and/or increased harvest index (HI). SHW-derived cultivars had shorter but wider flag leaves, with length : width ratio <10. The basal angle and open angle were small at the beginning of anthesis, which gradually increased as grain-filling progressed; the SPAD readings of the flag leaf and penultimate leaf of the SHW-derived cultivars was significantly higher than that of the non-synthetic cultivars from anthesis to mid–late grainfill. The CAP values at anthesis and 20 days post-anthesis were significantly higher in the SHW-derived cultivars than in non-synthetic cultivars, in which the difference was most significant between 10 : 00 and 12 : 00. The dry matter partitioning at anthesis varied significantly among cultivars, and the stem and sheath proportion of the SHW-derived cultivars was larger than that of the non-synthetic cultivars. At maturation, the spike rachis and leaves of the SHW-derived cultivars accounted for significantly smaller proportions of the total aboveground dry weight. Accordingly, the grain proportion was increased by 1–4 percentage points. Yield components were closely related to measured physiological parameters; e.g. grain yield correlated positively with SPAD values (r = 0.960**) and negatively with the proportion of spike rachis at maturation (r = –0.946**). This indicated that a semi-compact plant morphology, with high SPAD readings and high CAP and greater HI, was the physiological basis of high yield in SHW-derived cultivars.

Sunn pest (Eurygaster integriceps Puton) is currently widely distributed in West and Central Asia and Eastern Europe, but has not been found in Australia, Western Europe or North America. Climate warming is known to promote the expansion of its range of distribution, and it is expected that the insect could spread into new territories. Varieties of wheat (Triticum aestivum) carrying resistance remain an important component of managing the biosecurity risk of any potential incursion. Previous studies have identified sources of Sunn pest resistance in wheat, but there is little information on the genes that confer the resistance. This research used field-based, artificial infestation cages to evaluate 204 elite wheat varieties for Sunn pest resistance, at Terbol, Lebanon. A significant (P < 0.001) difference in resistance was observed among the wheat germplasm, with 19 varieties rated as resistant to moderately resistant and 17 as highly susceptible. Three of the elite varieties showed very little damage, a status similar to that of the resistant check, ICBW-209273. In parallel, the research carried out a genome-wide scan with single-nucleotide polymorphism (SNP) markers to identify chromosome regions and putative genes associated with resistance. Association mapping identified SNP markers with significant associations on chromosomes 2D, 4B and 5B. When these markers were projected onto the wheat population sequencing-based (POPSEQ) reference map, they tended to map close to the location of wheat height-reducing genes. The phenotypic variation explained by the identified markers ranged from 7% to 11%, and collectively, they explained 23.9% of the variation or 45% of the generalised heritability. Marker-trait association was confirmed in two independent, doubled-haploid wheat populations, derived from crosses involving wheat landraces from Afghanistan, where Sunn pest is recognised as an endemic problem. In the two wheat populations, the analyses validated the strong association between wsnp_BF483640B_Ta_2_2 and resistance to Sunn pest damage at the vegetative stage. This study demonstrates existence of genetic resistance to Sunn pest feeding at the vegetative stage in elite wheat germplasm. The study also identified and validated SNP markers that could be useful tools for transfer of resistance into new wheat cultivars.

Powdery mildew caused by the fungus Blumeria graminis f. sp. hordei (Bgh) is a global disease of barley, and the wild subspecies Hordeum vulgare subsp. spontaneum (Hvs) is the closest relative of cultivated barley (H. vulgare subsp. vulgare). The responses to the pathogen of 363 Hvs accessions maintained by the International Center for Agricultural Research in the Dry Areas (ICARDA) gene bank were assessed. Thirty non-Israeli pathogen isolates representing the global pathogenic diversity were used for testing. Because of genetic heterogeneity within 146 accessions, the results from only 217 accessions are presented and discussed. Additional tests on 152 accessions with homogeneous responses in earlier tests were made by using six Israeli pathogen isolates. There were 154 resistance phenotypes among the set, 141 of which involved single accessions. The six most frequent phenotypes were recorded for 62 accessions, with the most frequent phenotype in 26 accessions that were resistant to all 30 non-Israeli Bgh isolates. The second most frequent phenotype, found in 16 accessions, was susceptible to all 30 non-Israeli isolates. The occurrence of specific resistance was high. The occurrence of specific resistance was high and for breeding barley cultivars the effective resistances can be combined with the resistance gene mlo. In such combinations, the mlo gene prevents rapid increase in the pathogen population from overcoming the given specific resistance, whereas the resistance gene will simultaneously prevent erosion of mlo resistance. A more effective method for achieving durable resistance is accumulation minor resistance genes that are also widely distributed in wild barley.

Relationships between yield, biomass, radiation interception (PAR_int) and radiation-use efficiency (RUE) have been studied in many crops for use in growth analysis and modelling. Research in chickpea (Cicer arietinum L.) is limited, with variation caused by environment and phenological stage not adequately described. This study aims to characterise the variation in chickpea PAR_int and RUE with phenological stage, line and environment and their interactions, and the impact of this variation on yield. Chickpea lines (six desi and one kabuli) previously identified as varying for yield, competitive ability, crop growth rate and phenology were compared in four environments resulting from a combination of two sowing dates and dry and irrigated water regimes. Yield varied from 0.7 to 3.7 t ha^–1. Line, environment, phenological stage and the interactions line (G) × environment (E) and environment × stage affected both RUE and PAR_int. Line × stage interaction also affected RUE. High PAR_int and RUE were associated with high yield, but the interaction between environment and phenological stage dictated this relationship; higher PAR_int and RUE were observed in irrigated environments. Some environment × phenological stage combinations resulted in no significant associations, particularly before flowering in dry environments. These results emphasise the importance of understanding the effects of G × E on capture and efficiency in the use of radiation and have implications for growth analysis, modelling and breeding.

Seed weight can be an important component for soybean quality and yield. The objective of the present study was to identify quantitative trait loci (QTLs) for 100-seed weight by using 169 recombinant inbred lines (RILs) derived from the cross Williams 82 × PI 366121. The parental lines and RILs were grown for four consecutive years (2012–15) in the field. The seeds were harvested after maturity, dried and used to measure 100-seed weight. Analysis of variance indicated significant differences among the RILs for 100-seed weight. The environment had significant effect on seed-weight expression as indicated by the genotype × environment interaction. QTL analysis employing inclusive composite interval mapping of additive QTLs implemented in QTL IciMapping (Version 4.1) identified nine QTLs (LOD >3) on chromosomes 1, 2, 6, 8, 13, 14, 17 and 20. The individual QTLs explained phenotypic variation in the range 6.1–12.4%. The QTLs were detected in one or two environments, indicating major influence of the growing environment on seed-weight expression. Four QTLs identified in this study, qSW-02_1, qSW-06_1, qSW-13_1 and qSW-14_1, were found to be new QTLs. The findings of the study may be helpful to reveal the molecular genetic basis of the seed-weight trait in soybean.

This study is a continuation of our earlier reports on the identification and mapping of the Soybean mosaic virus (SMV) strain SC3 resistance gene present on chromosome 13 (LG F) of soybean (Glycine max (L.) Merr.). We used a combination of fine mapping and transcriptome sequencing to discover the candidate genes for SMV resistance in Qihuang-1. To fine-map the resistance gene, near-isogenic lines (NILs) from a cross between Qihuang-1 (resistant) and Nannong 1138-2 (susceptible) were genotyped with simple sequence repeats (SSR) and insertion and deletion (indel) markers to identify recombination events. Analysis of plants carrying key recombination events placed the resistance gene to a 180-kb region of the ‘Williams 82’ genome sequence with 17 annotated genes. Transcriptome and quantitative real-time PCR (qRT-PCR) analyses revealed that SMV resistance in Qihuang-1 was probably attributable to the four candidate genes (Glyma13g25920, Glyma13g25950, Glyma13g25970 and Glyma13g26000). The four candidate genes identified in this study can be used in further studies to investigate the role of resistance genes in conferring SC3 resistance in Qihuang-1.

This study was performed to identify marker loci associated with important agronomic traits and oil content under two moisture conditions and find stable associations in test environments in a worldwide collection of safflower (Carthamus tinctorius L.). Association analysis was conducted between eight important traits and 341 polymorphic AFLP markers produced by 10 primer combinations (EcoRI/MseI) in 100 safflower genotypes. The results of population structure analysis identified three main subpopulations possessing significant genetic differences revealed by analysis of molecular variance. Association analysis explained the highest percentage of trait variation for seed yield (38%) under drought-stress conditions and number of seeds per capitulum (27.75%) under normal conditions. Four markers (M51/E41-6, M51/E41-4, M61/E40-6 and M62/E40-17) in drought-stress conditions and two markers (M62/E40-35 and M47/E37-13) in normal conditions were simultaneously associated with seed and oil yield. The markers stably associated with traits in all test environments included M62/E40-35 with seed yield in normal conditions, M62/E40-17 with seed yield in drought stress conditions, and M62/E41-11 with oil yield in drought-stress conditions. Significant relationships were identified between oil content and three markers (M61/E40-6, M47/E37-8 and M51/E32-9) under drought-stress conditions, and three markers (M61/E2-2, M61/E40-6 and M51/E41-12) under normal conditions. Among them, M51/E32-9 and M61/E2-2 markers showed stable association with oil content under drought-stress and normal conditions, respectively. Detected markers would be useful in marker-assisted breeding programs for safflower improvement in arid and semi-arid area.

Many ryegrass cultivars are available on the market, but little research information exists on their comparative drought tolerance or the role of their commercially associated Epichloë endophytes in drought tolerance. Cloned plants of seven perennial ryegrass (Lolium perenne L.) cultivars (Grasslands Commando, Ceres One50, Banquet II, Alto, Bealey, Trojan and Avalon) and an unreleased elite line (URL) and one Mediterranean tall fescue (Festuca arundinacea Schreb.) cultivar (Grasslands Flecha), in all cases both endophyte-free (E–) and -infected (E ) plants, were subjected to a cycle of summer drought and rehydration from December 2012 to May 2013. Other clones of the same plants were irrigated. Insecticide was used to protect plants from insect attack. We report data for shoot dry matter (DM), tiller survival rate (TSR) and reproductive development assessed approximately monthly during the experiment. In the second month of drought, only Banquet II and Grasslands Flecha showed no significant shoot DM reduction under water deficit. After 3 months of drought, shoot DM was reduced by 43% (Flecha) to 85% (URL) compared with irrigated plants. For Banquet II, Avalon and Grasslands Flecha, TSR was not significantly reduced by water deficit. During rehydration, growth of previously non-irrigated plants typically exceeded growth of irrigated clones across all cultivars. Banquet II and Grasslands Flecha were drought-tolerant in the sense that they showed a lower percentage yield reduction under drought than other cultivars tested; this was in part because they were not among the highest yielding under irrigation. Irrespective of irrigation treatment, the shoot DM of E plants of ryegrasses URL (with AR37 endophyte) and One50 (with AR1 endophyte) was reduced by almost 50% relative to their E– counterparts in each harvest from December to May, whereas the other six ryegrass varieties generally showed a small trend towards reduced shoot DM as E plants. This indicates that some novel cultivar–endophyte associations can incur a yield disadvantage compared with E– plants when protected from insect pressure.

Leymus chinensis has important forage value and is considered a useful grass species for grassland restoration in Northeast China. However, little information exists concerning the germination responses of this species to interactions of cold stratification, light, temperature and low water potential caused by salinity and drought. Experiments were conducted in growth chambers, and the results showed that in all conditions of light, temperature and water stresses, the germination percentages of cold-stratified seeds were higher than of non-stratified seeds. Light had an inhibitory effect on germination percentage under both non-saline and salt stress conditions; darkness is beneficial for germination of this species. In addition, seeds germinated much better under alternating temperature regimes than under constant temperatures. Both salt and drought stresses decreased the germination percentage of Leymus chinensis, but the reductions under drought stress were much greater. Moreover, after being transferred to distilled water, most non-germinated seeds under drought stress germinated well, and the total percentage reached that of the non-saline condition level. Therefore, cold stratification is an effective measure to increase seed germination and salt or drought tolerance, especially in darkness. We conclude that Leymus chinensis has definite salt and drought tolerance during the germination stage and it is a promising species for the restoration of deteriorated grassland in Northeast China.