Head smut, caused by the fungal pathogen Sporisorium reilianum, poses a grave threat to maize (Zea mays) production worldwide. Here we report cytological and molecular evidence for maize resistance to head smut. During early stages of root infection, S. reilianum mycelium was capable of penetrating the root epidermis of both resistant (Ji1037) and susceptible (HZ4) inbred lines. S. reilianum hyphae were observed in the root-stem junction at 6 days after inoculation. In an attempt to monitor hyphal spread within the maize plant, a highly specific and sensitive real-time PCR method was established to estimate the hyphal content in infected maize tissues. During the upward growth of endophytic S. reilianum, the extent of hyphal spread was markedly different between Ji1037 and HZ4. Very little or no pathogen was detected in aerial parts of Ji1037, whereas large amounts of pathogen accumulated in aboveground tissues, particularly inflorescences, of HZ4. Thus, maize resistance to S. reilianum was achieved mainly by inhibition of endophytic hyphal growth rather than by prevention of early-root penetration by the pathogen.
Increasing plant density and improving N fertilizer rate along with the use of high density-tolerant genotypes would lead to maximizing maize (Zea mays L.) grain productivity per unit land area. The objective of this investigation was to match the functions of optimum plant density and adequate nitrogen fertilizer application to produce the highest possible yields per unit area with the greatest maize genotype efficiency. Six maize inbred lines differing in tolerance to low N and high density (D) [three tolerant (T); L-17, L-18, L-53, and three sensitive (S); L-29, L-54, L-55] were chosen for diallel crosses. Parents and crosses were evaluated in the 2012 and 2013 seasons under three plant densities: low (47,600), medium (71,400), and high (95,200) plants ha− 1 and three N fertilization rates: low (no N addition), medium (285 kg N ha− 1) and high (570 kg N ha− 1). The T × T crosses were superior to the S × S and T × S crosses under the low N-high D environment in most studied traits across seasons. The relationships between the nine environments and grain yield per hectare (GYPH) showed near-linear regression functions for inbreds L54, L29, and L55 and hybrids L18 × L53 and L18 × L55 with the highest GYPH at a density of 47,600 plants ha− 1 and N rate of 570 kg N ha− 1 and a curvilinear relationship for inbreds L17, L18, and L53 and the rest of the hybrids with the highest GYPH at a density of 95,200 plants ha− 1 combined with an N rate of 570 kg N ha− 1. Cross L17 × L54 gave the highest grain yield in this study under both high N-high-D (19.9 t ha− 1) and medium N-high-D environments (17.6 t ha− 1).
A 22-year field experiment was conducted in Gongzhuling, Jilin province, China to investigate corn yield response to fertilization practice. Compared to an unfertilized control (CK), all fertilization treatments, including inorganic nitrogen fertilizer only (N), balanced inorganic fertilizers (NPK), NPK plus corn straw (SNPK), and NPK plus farmyard manure (MNPK), resulted in significant increases in corn yield. However, only organic matter amendments sustained increasing yield trends, with annual rates of 0.137 and 0.194 t ha− 1 for the SPNK and MNPK treatments, respectively (P < 0.05). During the 22 years, the daily mean, maximum and minimum temperatures increased by 0.50, 0.53, and 0.46 °C per decade, whereas precipitation displayed no significant change but showed large seasonal variation. According to a regression analysis, increased air temperature exerted positive effects on corn yields under the SNPK and the MNPK treatments. Under both treatments, soil organic carbon contents and soil nutrient availabilities increased significantly compared to their initial levels in 1990, whereas soil bulk density and total porosity changed slightly under the two treatments, which showed higher soil water storage than other treatments. In contrast, significant increases in soil bulk density and decreases in soil total porosity and soil nutrient availability were observed under the CK, N and NPK treatments. The contributions of soil fertility to corn yield were 28.4%, 37.9%, 38.4%, 39.0%, and 42.9% under CK, N, NPK, SNPK, and MNPK treatments, respectively, whereas climate changes accounted for 27.0%, 14.6%, 12.4%, 11.8%, and 10.8%. These results indicate that, in Northeast China, organic matter amendments can mitigate negative and exploit positive effects of climate change on crop production by enhancing soil quality.
Conventional flat planting is commonly used for growing wheat in Pakistan and the crop is irrigated by flood irrigation, but it leads to ineffective use of applied nitrogen owing to poor aeration and leaching and volatilization losses. The practice also results in greater crop lodging, lower water use efficiency, and crusting of the soil surface. In contrast, bed planting of wheat not only saves water but improves fertilizer use efficiency and grain yield. Three years of pooled data from the present study showed that wheat planting on beds and nitrogen application at 120 kg ha− 1 produced 15.06% higher grain yield than flat planting at the same nitrogen rate. Similarly, 25.04%, 15.02%, 14.59%, and 29.83% higher nitrogen uptake, nitrogen use, and agronomic and recovery efficiencies, respectively, were recorded for bed compared to flat planting. Wheat planting on beds with a nitrogen application of 80 kg ha− 1 gave a yield similar to that of flat planting with 120 kg ha− 1 nitrogen. However, the economic return was 29% higher in bed planting as compared to flat planting, when nitrogen was applied at 120 kg ha− 1.
Chalkiness is one of the key factors determining rice quality and price. Ascorbic acid (Asc) is a major plant antioxidant that performs many functions in plants. l-Galactono-1,4-lactone dehydrogenase (l-GalLDH, EC1.3.2.3) is an enzyme that catalyzes the final step of Asc biosynthesis in plants. Here we show that the l-GalLDH-overexpressing transgenic rice, GO-2, which has constitutively higher leaf Asc content than wild-type (WT) plants, exhibits significantly reduced grain chalkiness. Higher foliar ascorbate/dehydroascorbate (Asc/DHA) ratios at 40, 60, 80, and 100 days of plant age were observed in GO-2. Further investigation showed that the enhanced level of Asc resulted in a significantly higher ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) protein level in GO-2 at 80 days. In addition, levels of abscisic acid (ABA) and jasmonic acid (JA) were lower in GO-2 at 60, 80, and 100 days. The results we present here indicate that the enhanced level of Asc is likely responsible for changing redox homeostasis in key developmental stages associated with grain filling and alters grain chalkiness in the l-GalLDH-overexpressing transgenic by maintaining photosynthetic function and affecting phytohormones associated with grain filling.
Production of mutants with altered phenotypes is a powerful approach for determining the biological functions of genes in an organism. In this study, a high-grain-weight mutant line M8008 was identified from a library of mutants of the common wheat cultivar YN15 treated with ethylmethane sulfonate (EMS). F2 and F2:3 generations produced from crosses of M8008 × YN15 (MY) and M8008 × SJZ54 (MS) were used for genetic analysis. There were significant differences between M8008 and YN15 in plant height (PH), spike length (SL), fertile spikelet number per spike (FSS), grain width (GW), grain length (GL), GL/GW ratio (GLW), and thousand-grain weight (TGW). Most simple correlation coefficients were significant for the investigated traits, suggesting that the correlative mutations occurred in M8008. Approximately 21% of simple sequence repeat (SSR) markers showed polymorphisms between M8008 and YN15, indicating that EMS can induce a large number of mutated loci. Twelve quantitative trait loci (QTLs) forming QTL clusters (one in MY and two in MS) were detected. The QTL clusters coinciding with (MY population) or near (MS population) the marker wmc41 were associated mainly with grain-size traits, among which the M8008 locus led to decreases in GW, factor form density (FFD), and TGW and to increases in GLW. The cluster in the wmc25-barc168 interval in the MS population was associated with yield traits, for which the M8008 locus led to decreased PH, spike number per plant (SN), and SL.
The response of seed germination to environmental factors can be estimated by nonlinear regression. The present study was performed to compare four nonlinear regression models (segmented, beta, beta modified, and dent-like) to describe the germination rate-temperature relationships of milk thistle (Silybum marianum L.) at six constant temperatures, with the aim of identifying the cardinal temperatures and thermal times required to reach different germination percentiles. Models and statistical indices were calibrated using an iterative optimization method and their performance was compared by root mean square error (RMSE), coefficient of determination (R2) and Akaike information criterion correction (AICc). The beta model was found to be the best model for predicting the required time to reach 50% germination (D50), (R2 = 0.99; RMSE = 0.004; AICc = − 276.97). Based on the model outputs, the base, optimum, and maximum temperatures of seed germination were 5.19 ± 0.79, 24.01 ± 0.11, and 34.32 ± 0.36 °C, respectively. The thermal times required for 50% and 90% germination were 4.99 and 7.38 degree-days, respectively.
Leaf rust (LR), caused by Puccinia triticina, is one of the most widespread diseases of common wheat (Triticum aestivum L.) worldwide. The LR resistance gene LrBi16 has been mapped on chromosome arm 7BL in Chinese wheat cultivar Bimai 16 and was closely linked to SSR loci Xcfa2257 and Xgwm344 with genetic distances of 2.8 cM and 2.9 cM, respectively. In the present study, a total of 304 AFLP primer pairs were used to screen Bimai 16 and Thatcher and resistant and susceptible DNA bulks. The polymorphic AFLP marker P-ATT/M-CGC173 bp was used to genotype F2 and F3 populations to identify markers more closely linked to LrBi16. Marker P-ATT/M-CGC173 bp was tightly linked to LrBi16 with a genetic distance of 0.5 cM. As LrBi16 was mapped near the Lr14a locus, 809 F2 plants from the Bimai 16/RL6013 (Lr14a) cross were inoculated with the Pt pathotype FHNQ to test the allelism of Lr14a and LrBi16. All of the F2 plants were resistant to FHNQ (IT between; and 2), suggesting that Lr14a and LrBi16 are allelic.
Mungbean (Vigna radiata L. Wilczek) is a short-duration legume crop cultivated for seeds that are rich in protein and carbohydrates. Mungbeans contain phytic acid (PA), an anti-nutritional factor that is the main storage form of organic phosphorus in seeds. It is a strong inhibitor against the absorption of nutrients including iron, zinc, calcium and magnesium in monogastric animals. Genotypes with low phytic acid (lpa) in seed may show increased assimilation of nutrients and be useful in breeding lpa cultivars. The present study was conducted to identify lpa sources, genetic variation, heritability, and association with seed coat color, inorganic phosphorus (IP), and seed size in 102 mungbean genotypes including released varieties, land races, mutants, and wild species grown in two seasons: summer 2011 and rabi 2012. PA and IP in dry seeds were estimated by modified colorimetric method and Chen's modified method, respectively. PA, IP, and 100-seed weight differed significantly in the two seasons. PA content in 102 genotypes ranged from 5.74 to 18.98 mg g− 1 and 5.85 to 20.02 mg g− 1 in summer 2011 and rabi 2012, respectively. High heritability was found for PA (0.87 and 0.86) and seed size (0.82 and 0.83) but low heritability for IP (0.61 and 0.60). A negative correlation was found between PA and seed size (r = − 0.183 and − 0.267). Yellow and green seed coat genotypes contained significantly less PA than black seed coat genotypes. Cluster analysis revealed the distinctness of wild species, land races and cultivated varieties on the basis of PA content. The genotypes YBSM (6.001 mg g− 1) and JL-781 (6.179 mg g− 1) showed lowest PA. These lpa sources can be used to develop high-yielding mungbean cultivars with low phytic acid.
With the widespread cultivation of transgenic crops, there is increasing concern about unintended effects of these crops on soil environmental quality. In this study, we used the Biolog method and ELISA to evaluate the possible effects of OsrHSA transgenic rice on soil microbial utilization of carbon substrates under field conditions. There were no significant differences in average well-color development (AWCD) values, Shannon-Wiener diversity index (H), Simpson dominance indices (D) and Shannon-Wiener evenness indices (E) of microbial communities in rhizosphere soils at eight samplings between OsrHSA transgenic rice and its non-transgenic counterpart. The main carbon sources utilized by soil microbes were carbohydrates, carboxylic acids, amino acids and polymers. The types, capacities and patterns of carbon source utilization by microbial communities in rhizosphere soils were similar throughout the detection period. We detected no OsrHSA protein in the roots of OsrHSA transgenic rice. We concluded that OsrHSA transgenic rice and the rHSA protein it produced did not alter the functional diversity of microbial communities in the rhizosphere.
