Abiotic stresses such as drought, salinity, and low temperature cause-losses in rice production worldwide. The emergence of transgenic technology has enabled improvements in the drought resistance of rice plants and helped avert crop damage due to drought stress. Selectable marker genes conferring resistance to antibiotics or herbicides have been widely used to identify genetically modified plants. However, the use of such markers has limited the public acceptance of genetically modified organisms. Marker-free materials (i.e., those containing a single foreign gene) may be more easily accepted by the public and more likely to find common use. In the present study, we created marker-free drought-tolerant transgenic rice plants using particle bombardment. Overall, 842 T₀ plants overexpressing the rice ascorbate peroxidase-coding gene OsAPX2 were generated. Eight independent marker-free lines were identified from T₁ seedlings using the polymerase chain reaction. The molecular characteristics of these lines were examined, including the expression level, copy number, and flanking sequences of OsAPX2, in the T₂ progeny. A simulated drought test using polyethylene glycol and a drought-tolerance test of seedlings confirmed that the marker-free lines carrying OsAPX2 showed significantly improved drought tolerance in seedlings. In the field, the yield of the wild-type plant decreased by 60% under drought conditions compared with normal conditions. However, the transgenic line showed a yield loss of approximately 26%. The results demonstrated that marker-free transgenic lines significantly improved grain yield under drought-stressed conditions.

Use of cytoplasmic male sterility (CMS) in hybrid breeding requires effective male fertility-restoring lines. In sorghum, very few restoring lines that can restore fertility in A₃ CMS have been reported. To identify the reasons for this deficiency, F₁ and F₂ hybrids of an A₃ CMS line crossed with the line IS1112C, a donor of fertility-restoring (Rf) genes for A₃ cytoplasm, and testcrosses of fertile plants to A₃ CMS lines were grown under contrasting water availability regimes in dryland and irrigated field plots. In the irrigated plots the frequency of fertile plants in testcrosses was twice that in dryland plots (P < 0.05). Fertile plants from the F₂ family grown in the irrigated plots showed significantly higher restoration ability than fertile plants from the same family grown in dryland plots. F₃ plants from the F₂ family grown in irrigated plots yielded on average a sixfold higher frequency of fertile plants in testcrosses than F₃ plants derived from dryland plots (P < 0.01). Fertility of testcross hybrids correlated negatively with air vapor pressure deficit (VPD) at flowering (r = − 0.96; P < 0.01) suggesting that VPD is a trigger for downregulation of Rf genes for A₃ cytoplasm.

Gliadins are the major components of storage proteins in wheat and play an important role in determining the extensibility properties of dough. In the present work, six novel full-length γ-gliadin genes were cloned from the C genome of Aegilops markgrafii using a PCR-based strategy. Analysis of the deduced amino acid sequences showed that the cloned genes had primary structures that were similar, but not identical, to published γ-gliadins from other wheat-related species. The lengths of the open reading frames (ORFs) ranged from 909 to 963 bp, and the repetitive and glutamine-rich domains were mainly responsible for the size of the proteins. An extra cysteine residue was present in the repetitive domain of sequence JX566513. All amino acid sequences of γ-gliadin genes from Ae. markgrafii were searched for the five peptides identified as T cell stimulatory epitopes in celiac disease (CD) patients. Peptide Gliγ-3 was present in sequences JX566513 and JX566514. Peptide Gliγ-5 was present only in JX566513. The other γ-gliadins contained no toxic epitopes. These results provide information to better understand the use of Ae. markgrafii in wheat breeding and the evolutionary relationship of the γ-gliadin genes in Ae. markgrafii and other Triticeae species.

Transposable element-based molecular markers can be utilized to investigate genetic diversity and to create genetic linkage maps. In this study, Class I and class II transposons were employed to obtain a comparative account of genetic diversity between wild and cultivated barley genotypes. Three types of PCR-based techniques were used: IMP (Inter MITE Polymorphism), IRAP (Inter-Retrotransposon Amplified Polymorphism) and REMAP (Retrotransposon-Microsatellite Amplified Polymorphism). Specific primer pairs for IMP, IRAP, and REMAP detected a total of 200 bands with an average of 20 bands per marker. The mean polymorphic information content (PIC) and discrimination power (D) values in all 47 genotypes from these three types of transposon-based polymorphisms were 0.910 and 0.935, respectively. Unweighted Pair Group Method with Arithmetic mean (UPGMA)-based cluster analysis classified all 47 genotypes, both wild and cultivated, into separate groups consistent with their geographical origins. Sequencing followed by chromosome location of polymorphic bands enables precise gene introgression from wild gene pool to cultivated barley. The highly polymorphic nature of these marker systems makes them suitable for use in varietal identification and MAS-based breeding programs in barley and other cereals.

Extreme high temperatures detrimental to maize production are projected to occur more frequently with future climate change. Phenology and yield-related traits were investigated under several levels of elevated temperature in two early-maturing hybrid cultivars: Junda 6 (grown in northeastern China) and Chalok 1 (grown in South Korea). They were cultivated in plastic houses in Suwon, Korea (37.27°N, 126.99°E) held at target temperatures of ambient (AT), AT+1.5°C, AT+3°C, and AT+5°C at one sowing date in 2013 and three different sowing dates in 2014. Vegetative and reproductive growth durations showed variation depending on sowing date, experimental year, and cultivar. Growth duration tended to decrease, but not necessarily, with temperature elevation, but somewhat increased again above a certain temperature. High temperature-dependent variation was greater during grain filling than in the vegetative period before anthesis. Elevated temperature showed no significant effects on duration or peak dates of silking and anthesis, and thus on anthesis-silking interval. Grain yield tended to decrease with temperature elevation above ambient, showing a sharper linear decrease with mean growing season temperature increase in Junda 6 than in Chalok 1. The decrease in kernel number accounted for a much greater contribution to the yield reductions due to temperature elevation than did the decrease in individual kernel weight in both cultivars. Individual harvestable kernel weight was not significantly affected by temperature elevation treatments. Kernel number showed a linear decrease with mean growth temperature from early ear formation to early grain-filling stage, with Junda 6 showing a much severer decrease than Chalok 1. Kernel number reduction due to temperature elevation was attributable more to the decrease in differentiated ovule number than to the decrease in kernel set in Chalok 1, but largely to the decrease of kernel set in Junda 6.

Projected changes in weather parameters, mainly temperature and rainfall, have already started to show their effect on agricultural production. To cope with the changing scenarios, adoption of appropriate management strategies is of paramount importance. A study was undertaken to evaluate the most appropriate combination of sowing date and phosphorus fertilization level for peanut crops grown in sandy loam soil in a subhumid region of eastern India. Field experiments were conducted during the summer seasons of 2012 and 2013 on peanut crops at the farm of the Indian Institute of Technology, Kharagpur. The DSSAT v4.5 CROPGRO-Peanut model was used to predict the phenology, growth, and yield of peanut crop under combinations of four sowing dates and four phosphorus fertilization levels. The model was calibrated with a 2012 dataset of growth, phenology, and yield parameters for estimating the genetic coefficients of cultivar TMV-2 and was validated with a 2013 dataset of the same parameters. Simulations of pod yield and other yield parameters using the calibrated model were found to be quite accurate. The model was able to reasonably simulate pod yield and final biomass with low normalized root mean square error (RMSE_n), low absolute root mean square error (RMSE_a) and high coefficient of determination (R² > 0.7) over a wide range of sowing dates and different phosphorus fertilization levels sensitivity analysis indicated that sowing from the second week of January to the end of February with 30-50 kg P₂O₅ ha^{− 1} would give the highest pod yield.

The development of a core set of SNP molecular markers that could be widely used in soybean genetic research would greatly facilitate research into the genetic diversity of soybean. We conducted an analysis of Tokachi nagaha and 137 of its descendant soybean cultivars using 4044 SNP markers with the goal of determining the appropriate number of single-nucleotide polymorphisms (SNPs) needed to construct unambiguous molecular IDs and characterize genetic diversity based on a genetic distance matrix correlation method. When the number of SNPs was held constant, the number of accession pairs that could be distinguished increased as the polymorphism informative content (PIC) value of the SNPs increased. A core panel of 20 selected SNPs from 11 linkage groups with a mean PIC value of 0.3703 and a range of 0.3640-0.3749 was able to identify almost all of the accession pairs in our study [9445 pairs (99.92%)]. The eight accession pairs that could not be identified with this core SNP set all originated from the same province and some of them had the same parental cultivars. The molecular IDs of the 138 accessions were constructed using the core 20 SNPs. It is known that both the number of SNPs and PIC values should be considered when SNPs are selected for use in the analysis of genetic diversity. In this study, when the PIC value was 0.3460, the correlation coefficient between the genetic distance matrices associated with a panel of 200 SNPs and the total population was > 0.800, indicating satisfactory correlation. Our high-accuracy, high-resolution core SNP panel for germplasm fingerprinting and our findings about assessing genetic diversity will likely markedly improve the management and utilization efficiency of soybean germplasm resources.

In view of the prospect of irregular extremes of high and low rainfall due to climate change, the mechanisms underlying plant responses to periods of drought and re-watering need to be understood. Sorghum (Sorghum bicolor L.) and maize (Zea mays L.) were grown in pots of loess soil at three soil moisture levels to examine the effects of different levels of drought over 10 days and plant responses to re-watering (5 days of rehydration). Photosynthesis-related traits recovered rapidly both in sorghum and maize on re-watering, suggesting that photosynthetic function was not severely damaged after a short drought period, although the values of these traits were dramatically reduced during drought per se. However, the two species differed in the extent to which they recovered from severe stress. In sorghum, net photosynthetic rate (P_n), stomatal conductance (G_s), and maximum photochemical efficiency of PSII (F_v/F_m) returned to control levels after re-watering. However, in maize, these parameters exceeded control levels after re-watering. Both overcompensation and pre-drought limitation were observed. Over a range of growth conditions, close relationships between G_s and root hydraulic conductance (K_r) were observed in pooled data sets. P_n, K_r, and their related characteristics were compared among species and treatments. Our results showed that the recovery of K_r is similar between sorghum and maize, at least after a short time of re-watering, although the two species differ in drought-tolerance capacity. Our results also suggest that sorghum can endure moderate drought by adjusting certain traits, but is still as vulnerable as maize under severe drought stress.

Climate change is affecting global crop productivity, food quality, and security. However, few studies have addressed the mechanism by which elevated CO₂ may affect the growth of medicinal plants. Isatis indigotica Fortune is a widely used Chinese medicinal herb with multiple pharmacological properties. To investigate the physiological mechanism of I. indigotica response to elevated [CO₂], plants were grown at either ambient [CO₂] (385 μmol mol^{− 1}) or elevated [CO₂] (590 μmol mol^{− 1}) in an open-top chamber (OTC) experimental facility in North China. A significant reduction in transpiration rate (T_r) and stomatal conductance (g_s) and a large increase in water-use efficiency contributed to an increase in net photosynthetic rate (P_n) under elevated [CO₂] 76 days after sowing. Leaf non-photochemical quenching (NPQ) was decreased, so that more energy was used in effective quantum yield of PSII photochemistry (Φ_PSII) under elevated [CO₂]. High Φ_PSII, meaning high electron transfer efficiency, also increased P_n. The [CO₂]-induced increase in photosynthesis significantly increased biomass by 36.8%. Amounts of metabolic compounds involved in sucrose metabolism, pyrimidine metabolism, flavonoid biosynthesis, and other processes in leaves were reduced under elevated [CO₂]. These results showed that the fertilization effect of elevated [CO₂] is conducive to increasing dry weight but not secondary metabolism in I. indigotica.