Stem growth habit is an important agronomic trait in soybean and is subject to artificial selection. This study aimed to provide a theory for genotypic selection of stem growth habit for breeding purposes by analyzing the alleles of GmTfl1 gene in Chinese soybean varieties and establishing a database of GmTfl1 variation. Using knowledge of insertion and deletion (Indel) in the non-coding region and four single-nucleotide polymorphisms (SNPs) in the coding sequences of the GmTfl1 gene, four CAPS and one Indel markers were developed and used to test 1120 Chinese soybean varieties. We found that the dominant GmTfl1 allele was prevalent in accessions from the Northern ecoregion, whereas the recessive allele, Gmtfl1, was more common in the Southern ecoregion, and the proportions of GmTfl1 and recessive alleles were respectively 40.1% and 59.9% in the Huang-Huai ecoregion. The proportion of GmTfl1 decreased and that of Gmtfl1 increased, gradually from north to south. Allele GmTfl1-a was present in higher proportions in the Huang-Huai spring, Huang-Huai summer, and Northern spring sub-ecoregions than that in the other sub-ecoregions. GmTfl1-b was common in the Northeast spring, Northern spring and Southern summer sub-ecoregions. Gmtfl1-ta was found mainly in the Huang-Huai spring, Huang-Huai summer and Southern spring sub-ecoregions. The Gmtfl1-ab allele was distributed in all six soybean sub-ecoregions. The Gmtfl1-bb allele was distributed mainly in the Huang-Huai spring and summer and Southern spring and summer sub-ecoregions, but the Gmtfl1-tb allele was detected only in the Huang-Huai summer sub-ecoregion. The distributions of GmTfl1 and Gmtfl1 have shown no large changes in nearly 60 years of breeding, but the frequency of the recessive genotype Gmtfl1 has shown a rising trend in the last 20 years. This study provides a theoretical foundation for breeding new soybean varieties for different ecoregions.
Plants may respond to drought by altering biomass allocation to shoots and roots or by changing the metabolic activities in these organs. To determine how drought changes the partitioning of carbon allocated to growth and secondary metabolism in maize roots and how it affects photosynthesis (A) and productivity in maize, we evaluated leaf gas exchange, yield componentes, root morphology, and primary and secondary metabolites including total soluble sugars (TSS), starch (S), phenolics (PHE), and lignin (LIG). Data were collected from pot-grown plants of four maize genotypes: BRS 1010 and 2B710 (sensitive genotypes) and DKB390 and BRS1055 (tolerant genotypes) under two soil water tensions: field capacity (FC, − 18 kPa) and water deficit (WD, − 138 kPa). WD was applied at the pre-flowering stage for 12 days and then the water supply was restored and maintained at optimum levels until the end of the cycle. For genotype BRS 1055 under FC, the greatest A did not result in greater grain biomass (DGB) because the accumulated photoassimilates had already filled the cells, and thus the excessive TSS synthesized in leaves was allocated to roots in large amounts. However, the sharp decrease in A caused by WD imposition in this genotype did not affect the influx pressure of leaf TSS, which was due largely to conversion of primary metabolites to PHE compounds to increase the length of fine roots. In leaves of DKB390 under WD, both S and TSS were reduced, whereas PHE were increased to prevent excessive water loss and xylem cavitation. Under WD, both BRS1010 and 2B710 genotypes displayed reduced allocation of biomass to shoots and roots and LIG content in leaves, as well as lower A and DGB values. In BRS1010 this response was coupled to S decrease in leaves and TSS increase in roots, whereas in 2B710 there was a concomitant S increase in roots.
Soil phosphorus (P) fractionation, adsorption, and desorption isotherm, and rice yield and P uptake were investigated in flooded tropical rice (Oryza sativa L.) following 42-year fertilizer and manure application. The treatments included low-input [unfertilized control without N, P, or K (C0N0)], farmyard manure (FYM) (C1N0), NP (C0NP), NPK (C0NPK), FYM + NP (C1NP), and high-input treatment, FYM + NPK (C1NPK). Grain yield was increased significantly by 74% over the control under the combined application of FYM + NPK. However, under low- and high-input treatments, yield as well as P uptake was maintained at constant levels for 35 years. During the same period, high yield levels and P uptake were maintained under the C0NP, C0NPK, and C1NPK treatments. These are unique characteristics of a tropical flooded ecosystem, which is a self-sustaining system for rice production. The Fe-P fraction was highest compared to the Ca-P and Al-P fractions after 42 years of fertilizer application and was significantly higher under FYM + NPK treatment. The P adsorption capacity of soil was highest under the low-input treatment and lowest under long-term balanced fertilization (FYM + NPK). In contrast, P desorption capacity was highest under NPK and lowest in the control treatment. Long-term balanced fertilization in the form of FYM + NPK for 42 years lowered the bonding energy and adsorption capacity for P in soil but increased its desorption potential, increasing P availability to the plant and leading to higher P uptake and yield maintenance.
Differences in soil physical, chemical and biological properties between paddy-upland and continuous upland rotations will influence nutrient relations and crop growth. With the aim of estimating rapeseed yield performance in response to fertilization in rice-rapeseed (RR) and cotton-rapeseed (CR) rotations, on-farm experiments were conducted at 70 sites across Hubei province, central China. The economically optimal fertilizer rates of winter oilseed rape in different rotations were determined. Field experiments showed that previous crops significantly influenced seed yields. Without N fertilization, seed yields were significantly lower for the RR rotation than for the CR rotation. The average yield increase ratio and agronomic efficiency associated with nitrogen (N) fertilization in the RR rotation were 96.6% and 6.56 kg kg− 1, significantly higher than those in the CR rotation. No seed yield differences were detected between the two rotations under phosphorus (P) and potassium (K) fertilization. In contrast to the CR rotation, N fertilizer played a more vital role in maintaining high seed yields in the RR rotation owing to the lower indigenous soil N supply. Compared with local N fertilizer recommendation rates for the RR rotation, on average an additional 18 kg N ha− 1 was recommended according to the economically optimal N fertilizer rate (EONFR). In contrast, the EONFR was 14 kg N ha− 1 lower than the locally recommended N fertilizer rate for the CR rotation. There were no differences between the two rotations for the average economically optimal P and K fertilization rates. Consequently, the average EONFR of winter oilseed rape could be reduced if cotton rather than rice preceded the winter oilseed rape.
Aegilops tauschii Ais a wild relative of common wheat (Triticum aestivum) and acts as an important resource of elite genes including genes for resistance to biotic and abiotic stresses. To improve the cadmium (Cd) tolerance of wheat varieties using A. tauschii resources, we investigated the genetic variation of biomass-based Cd tolerance in 235 A. tauschii accessions treated with 0 (control) and 100 μmol L− 1 CdCl2 (as Cd stress). Simultaneously, we performed a genomewide association study (GWAS) using a single-nucleotide polymorphism chip containing 7185 markers. Six markers were found to be significantly associated with Cd tolerance by a general linear model and a mixed linear model. These markers were close to several candidate/flanking genes associated with Cd tolerance according to results in public databases, including pdil5-1, Acc-1, DME-5A, TaAP2-D, TaAP2-B, Vrn-B1, and FtsH-like protein gene. The A. tauschii accessions were classified as high, moderate, and low Cd-tolerant according to a secondary index, the synthetic index (SI), in proportions of 9%, 57%, and 34%, respectively. By the average SI, accessions from Afghanistan, Turkey, Azerbaijan, and Iran showed relatively high Cd tolerance.
Genetic diversity analysis and DNA finger printing are very useful in breeding programs, seed conservation and management. Jute (Corchorus spp.) is the second most important natural fiber crop after cotton. DNA fingerprinting studies in jute using SSR markers are limited. In this study, 58 jute accessions, including two control varieties (Huangma 179 and Kuanyechangguo) from the official variety registry in China were evaluated with 28 pairs of SSR primers. A total of 184 polymorphic loci were identified. Each primer detected 3 to 15 polymorphic loci, with an average of 6.6. The 58 jute accessions were DNA-fingerprinted with 67 SSR markers from the 28 primer pairs. These markers differentiated the 58 jute accessions from one another, with CoSSR305-120 and CoSSR174-195 differentiating Huangma 179 and Kuanyechangguo, respectively. NTSYS-pc2.10 software was used to analyze the genetic diversity in the 58 jute accessions. Their genetic similarity coefficients ranged from 0.520 to 0.910 with an average of 0.749, indicating relatively great genetic diversity among them. The 58 jute accessions were divided into four groups with the coefficient 0.710 used as a value for classification, consistent with their species and pedigrees. All these results may be useful both for protection of intellectual property rights of jute accessions and for jute improvement.
Biotic and abiotic stresses are major limiting factors for high crop productivity worldwide. A landrace collection consisting of 380 durum wheat (Triticum turgidum L. var. durum) entries originating in several countries along with four check varieties were evaluated for biotic stresses: yellow rust (Puccinia striiformis Westendorf f. sp. tritici) and wheat stem sawfly (WSS) Cephus cinctus Norton (Hymenoptera: Cephidae), and abiotic stresses: cold and drought. The main objectives were to (i) quantify phenotypic diversity and identify variation in the durum wheat landraces for the different stresses and (ii) characterize the agronomic profiles of landraces in reaction to the stresses. Significant changes in reactions of landraces to stresses were observed. Landraces resistant to each stress were identified and agronomically characterized. Percentage reduction due to the stresses varied from 11.4% (yellow rust) to 21.6% (cold stress) for 1000-kernel weight (TKW) and from 19.9 (yellow rust) to 91.9% (cold stress) for grain yield. Landraces from Asia and Europe showed enhanced genetic potential for both grain yield and cold tolerance under highland rainfed conditions of Iran. The findings showed that TKW and yield productivity could be used to assess the response of durum wheat landraces to different stresses. In conclusion, landraces showed high levels of resistance to both biotic and abiotic stresses, and selected landraces can serve in durum wheat breeding for adaptation to cold and drought-prone environments.
The ameliorative effect of fulvic acid (0, 300, and 600 mg L− 1) on photosystem II and antioxidant enzyme activity of the rapeseed (Brassica napus L.) plant under water stress (60, 100, and 140 mm evaporation from class A pan) was studied using split plots in a randomized complete block design with three replications. Results indicated that application of fulvic acid (FA) improved the maximum quantum efficiency of PSII (Fv/Fm) and performance index (PI) of plants under both well-watered and limited-water conditions. The time span from Fo to Fm and the energy necessary for the closure of all reaction centers was significantly increased, but the size of the plastoquinone pool was reduced with increasing water stress levels. Plants treated with FA had higher peroxidase and catalase activities under all irrigation conditions. Activities of ascorbate peroxidase and superoxide dismutase in plants increased with increasing water stress. Malondialdehyde increased under severe water stress, but application of FA significantly decreased lipid peroxidation. Production of reactive oxygen species (ROS) is a common phenomenon in plants under stress. Under this condition, the balance between the production of ROS and the quenching activity of antioxidants is upset, often resulting in oxidative damage. In this study, application of FA significantly increased fluorescence of chlorophyll a, inhibiting ROS production and enhancing antioxidant enzymes activity that destroyed ROS. Thus, ROS in plant cells was reduced under water stress by application of FA and consequently lipid peroxidation was reduced.
Breeding for salinity tolerance using Bangladeshi rice landraces and understand genetic diversity has been limited by the complex and polygenic nature of salt tolerance in rice genotypes. A genetic diversity and association mapping analysis was conducted using 96 germplasm accessions with variable response to salt stress at the seedling stage. These included 86 landraces and 10 indica varieties and lines including Nona Bokra, from southern Bangladesh. A total of 220 alleles were detected at 58 Simple Sequence Repeat (SSR) marker loci randomly distributed on all 12 rice chromosomes and 8 Sequence Tagged Site (STS) markers developed for genes SKC1, DST, and SalT. The average gene diversity was 0.5075 and polymorphism information content value was 0.4426, respectively. Cluster analysis revealed that 68 and 21 accessions were clustered into 2 distinct groups, possibly corresponding to indica and japonica groups, respectively and the remaining 7 landraces were classified as an admixed group. In addition to Wn11463, the STS marker for SKC1, RM22418 on Chr. 8 was significantly associated with salinity tolerance, at the location of a QTL detected in previous studies. Our findings of favorable alleles associated with salinity tolerance in Bangladeshi rice landraces, as well as the development of STS markers for salt tolerance genes, will be helpful in future efforts to breed salinity tolerance in rice.
A two-year field experiment (2012-2013) was conducted to investigate the effects of two tillage methods and five maize straw mulching patterns on the yield, water consumption, and water use efficiency (WUE) of spring maize (Zea mays L.) in the northern Huang-Huai-Hai valley of China. Compared to rotary tillage, subsoil tillage resulted in decreases in water consumption by 6.3-7.8% and increases in maize yield by 644.5-673.9 kg ha− 1, soil water content by 2.9-3.0%, and WUE by 12.7-15.2%. Chopped straw mulching led to higher yield, soil water content, and WUE as well as lower water consumption than prostrate whole straw mulching. Mulching with 50% chopped straw had the largest positive effects on maize yield, soil water content, and WUE among the five mulching treatments. Tillage had greater influence on maize yield than straw mulching, whereas straw mulching had greater influence on soil water content, water consumption, and WUE than tillage. These results suggest that 50% chopped straw mulching with subsoil tillage is beneficial in spring maize production aiming at high yield and high WUE in the Huang-Huai-Hai valley.
