Improve Lodging Resistance Research Articles

Fine mapping of the BnUC2 locus related to leaf up-curling and plant semi-dwarfing in Brassica napus

BackgroundStudies of leaf shape development and plant stature have made important contributions to the fields of plant breeding and developmental biology. The optimization of leaf morphology and plant height to improve lodging resistance and photosynthetic efficiency, increase planting density and yield, and facilitate mechanized harvesting is a desirable goal in Brassica napus.ResultsHere, we investigated a B. napus germplasm resource exhibiting up-curled leaves and a semi-dwarf stature. In progeny populations derived from NJAU5737 and Zhongshuang 11 (ZS11), we found that the up-curled leaf trait was controlled by a dominant locus, BnUC2. We then fine mapped the BnUC2 locus onto an 83.19-kb interval on chromosome A05 using single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers. We further determined that BnUC2 was a major plant height QTL that explained approximately 70% of the phenotypic variation in two BC5F3 family populations derived from NJAU5737 and ZS11. This result implies that BnUC2 was also responsible for the observed semi-dwarf stature. The fine mapping interval of BnUC2 contained five genes, two of which, BnaA05g16700D (BnaA05.IAA2) and BnaA05g16720D, were revealed by comparative sequencing to be mutated in NJAU5737. This result suggests that the candidate gene mutation (BnaA05g16700D, encoding Aux/IAA2 proteins) in the conserved Degron motif GWPPV (P63S) was responsible for the BnUC2 locus. In addition, investigation of agronomic traits in a segregated population indicated that plant height, main inflorescence length, and branching height were significantly reduced by BnUC2, whereas yield was not significantly altered. The determination of the photosynthetic efficiency showed that the BnUC2 locus was beneficial to improve the photosynthetic efficiency. Our findings may provide an effective foundation for plant type breeding in B. napus.ConclusionsUsing SNP and SSR markers, a dominant locus (BnUC2) related to up-curled leaves and semi-dwarf stature in B. napus has been fine mapped onto an 83.19-kb interval of chromosome A05 containing five genes. The BnaA05.IAA2 is inferred to be the candidate gene responsible for the BnUC2 locus.

Biomechanical Properties and Agro-Morphological Traits for Improved Lodging Resistance in Ethiopian Teff (Eragrostis tef (Zucc.) Trottor) Accessions

Susceptibility to lodging is a major constraint on teff production in Ethiopia, but efforts to develop lodging-resistant cultivars have not been successful. We studied the mechanical properties of teff culms and associated agro-morphological traits in field experiments with 320 teff accessions at two sites in northwestern Ethiopia during the 2018 and 2019 growing seasons. The results showed significant variability in both mechanical properties and agro-morphological traits among accessions. Traits contributing to lodging resistance, such as internode diameter, pushing resistance, and base failure moment, were significantly positively correlated with each other and with plant height. Similarly, the correlation of those traits with lodging index was significant and positive. In contrast, tiller number showed a significant negative correlation with lodging index. The peduncle–panicle length, which generally accounted for 59% of the plant height, should be a target when breeding for semi-dwarfism. Root system development, which reached a depth of more than 1 m in tall and 57 cm in dwarf teff accessions, signifies the presence of genetic variabilities for future root lodging studies in teff, and it may also explain why teff performs well in drought-prone areas of Ethiopia. Breeding programs for lodging resistance might focus on accessions with good standing ability (high base failure moment) and introgression of stem strength with a semi-dwarf phenotype. Alternatively, selection for a large internode diameter, increased pushing resistance and base failure moment, and a reduced tiller number should be considered.

Identification and molecular mapping of the semi-dwarf locus (sdf-1) in soybean by SLAF-seq method

Plant height is one of the most important agronomic traits in soybean. The semi-dwarf soybean cultivars could improve lodging resistance and solar radiation use efficiency so as to increase soybean yield. However, the inheritance of semi-dwarf traits has not been intensively studied and few semi-dwarf genes have been isolated in soybean. In this study, we use specific-length amplified fragment sequencing (SLAF-seq) with bulked segregant analysis (BSA) to map the semi-dwarf gene in soybean. Plant height of 213 F2:3 families, derived from a cross between ‘Jimidou-1’ (semi-dwarf) and ‘Gongjiao9112’ (tall), was evaluated under field conditions. Genetic analysis indicated that the semi-dwarf trait was controlled by one single recessive gene. Associated with the semi-dwarf trait, SLAF-seq combined with BSA was used to develop polymorphic SLAF markers and identify a 1.04 Mb genomic region, which was designated as sdf-1. The sdf-1 locus was delimited to 80.72 kb region on chromosome 19 by KASP SNP markers developed from the SLAF markers and 6 K SNP chip. There were 14 putative genes in the associated region. From annotation information, three genes (Glyma.19g194800, Glyma.19g194500 and Glyma.19g195200) might be interesting candidate genes that are highly related to plant height growth or semi-dwarf trait. The successful identification and localization of sdf-1 could help reveal molecular mechanisms underlying soybean semi-dwarfism and to indirectly improve total yield.

Traits of plant morphology, stalk mechanical strength, and biomass accumulation in the selection of lodging-resistant maize cultivars

• There is no correlation in current maize cultivar’s resistance to stalk or root lodging. • Stalk breakage is primarily affected by dry weight per unit length during grain filling. • Vertical root pulling resistance is primarily affected by the ratio of root depth to width. • High ratios of shoot fresh weight to vertical root pulling resistance increase maize root lodging risk. Lodging resistance is a major desired trait in modern maize breeding. Identifying parameters to evaluate lodging resistance could help crop breeders develop maize cultivars with improved lodging resistance. Thirty-four summer maize cultivars currently planted in China were grown in 2017 and 2018 in order to identify relationships between stalk and root lodging resistance and to analyze the main reasons for differences in lodging resistance between maize cultivars. Twenty-five lodging resistance indicators, including aspects of morphology, dry matter, moisture content, and the mechanical strength of the stalk and root, were investigated at silking and 35 d after silking. The experiments showed that the ratio of shoot fresh weight to vertical root pulling resistance (VRPR) was a better indicator of root lodging potential than VRPR alone. Stalk breaking force was not associated with VRPR and was significantly positively correlated with shoot fresh weight/VRPR. Classification of the 34 cultivars revealed that resistance to stalk and root lodging were not correlated. Correlation and regression analyses revealed that approximately 63 % of the breaking force was explained by the average dry weight per unit length (DWUL) of the basal three internodes, ear height, and fresh weight of the basal three internodes at silking. At 35 d after silking, approximately 88 % of the difference in breaking force was explained by the plant height, ear ratio, crush strength (CS) of the fourth internode, average DWUL and fresh weight per unit volume (FWUV) of the basal three internodes. The main indicator affecting VRPR was the ratio of root depth to width at 35 d after silking. Therefore, an important strategy for increasing maize lodging resistance is to breed cultivars with high internode DWUL, low ear position, and deep roots.

Genetic progress in stem lodging resistance of the dominant wheat cultivars adapted to Yellow-Huai River Valleys Winter Wheat Zone in China since 1964

Analysis of genetic progress for lodging-related traits provides important information for further improvement of lodging resistance. Forty winter wheat cultivars widely grown in the Yellow-Huai River Valleys Winter Wheat Zone (YHWZ) of China during the period of 1964–2015 were evaluated for several lodging-related traits in three cropping seasons. Plant height, height at center of gravity, length of the basal second internode, and lodging index decreased significantly in this period, and the average annual genetic gains for these traits were −0.50 cm or −0.62%, −0.27 cm or −0.60%, −0.06 cm or −0.63%, and −0.01 or −0.94%, respectively. Different from other traits, stem strength showed a significant increasing trend with the breeding period, and the annual genetic gains were 0.03 N or 0.05%. Correlation analysis showed that lodging index was positively correlated with plant height, height at center of gravity, and length of the basal second internode, but negatively correlated with stem strength. Meanwhile, significantly positive correlations were observed between plant height, height at center of gravity, and length of the basal first and second internodes. By comparison with the wild types, dwarfing genes had significant effects on all lodging-related traits studied except for length of the basal first internode and stem strength. Principle component analysis demonstrated that plant height and stem strength were the most important factors influencing lodging resistance. Clustering analysis based on the first two principle components further indicated the targets of wheat lodging-resistant breeding have changed from reducing plant height to strengthening stem strength over the breeding periods. This study indicates that the increase of stem strength is vital to improve lodging resistance in this region under the high-yielding condition when plant height is in an optimal range.

GAR dwarf gene Rht14 reduced plant height and affected agronomic traits in durum wheat (Triticum durum)

The GA-insensitive dwarf genes, Rht-B1b (Rht1) and Rht-D1b (Rht2), have been used worldwide for reducing plant height, improving lodging resistance and grain yield since the Green Revolution. To explore new dwarf genes for wheat improvement, in this study, the effects of GA-responsive (GAR) dwarf gene, Rht14, on plant height related traits, agronomic traits, yield traits and quality traits were evaluated in durum wheat by F2:3 lines, F3:4 lines and F4:5 lines that derived from reciprocal crosses between the Rht14 donor Castelporziano (CP) and Langdon (L). These results indicated that Rht14 could reduce plant height by an average of 26.68 % and 27.68 % in the lines of CP × L and L × CP populations, respectively. Furthermore, both the length of peduncle and each internode were all significantly reduced, with the basal one as the most proportion and the peduncle as the largest difference. The flag leaf length, width and area increased significantly in dwarf lines. Rht14 did not affect most of the yield components, including number of tillers plant−1, number of fertile tillers plant−1, spikelet number spike−1, grain number spike−1, biomass plant−1, grain yield plant−1, while significantly decreased 1000-kernel weight. Rht14 didn’t affect the length of coleoptile and seedling root traits when compared with tall lines, indicating it may have the potential for good seedling establishment in the field. A negative effect of Rht14 on some quality traits was observed. The results indicate that GAR dwarf gene Rht14 represents a new alternative locus in breeding programs for improving population yield potential and lodging resistance in wheat.

The role of ridge‐furrow with plastic film mulching system on stem lodging resistance of winter wheat in a dry semi‐humid region

AbstractRidge‐furrow with plastic film mulching (RFPFM) is widely used as a water‐saving strategy for the improvement of crop yield. However, lodging susceptibility under RFPFM practices has not yet been determined. A 2‐yr field study comprising of three cultivation strategies (rain‐fed flat planting [FP], RFPFM, and well‐water planting [WW]) and two N application rates (75 and 225 kg N ha–1) was conducted to assess the risk of lodging and the relationship between lodging resistance and grain yields of two wheat (Triticum aestivum L.) varieties (Xinong979 as lodging resistant and Xiaoyan22 as lodging susceptible). The results showed that higher N application increased lodging index under FP and RFPFM, and the lodging index was 33% lower under RFPFM than under WW. In both years, there was a positive relationship between grain yield and lodging susceptibility (R2 = 0.62** and 0.57**) implying that promoting crop yield by using RFPFM strategy accelerates the risk of lodging. When compared with WW, RFPFM significantly reduced the lodging index, while sustaining a comparable grain yield. Overall, RFPFM could be highly recommended as a promising strategy for winter wheat producers in dry, semi‐humid regions. The close relationships of breaking resistance and lodging index with both mass density and stem wall thickness of basal internode suggest that selection for increased stem strength trait could lead to improved lodging resistance and higher yields in future programs for winter wheat cultivar improvement.

The genetic architecture of biomechanical traits in sorghum

AbstractSorghum bicolor (L.) Moench is the fifth most commonly grown cereal crop worldwide with unrivaled drought tolerance compared with other cereal crops. Drought and heat tolerance and high biomass yield potential make sorghum a promising bioenergy crop. However, stem lodging is a significant problem that results in substantial yield losses. Stem biomechanical traits influence the mechanical stability of crops and breeding for desirable biomechanical traits may result in improved lodging resistance. In this study, we report the identification of quantitative trait loci (QTL) for stem mechanical and morphological traits in three recombinant inbred line (RIL; populations from Tx623/Rio, Tx623/Della, and Tx631/Della) crosses between elite grain and sweet sorghum parents. The genetic architecture of stem biomechanical traits in the three RIL populations is multigenic and pleiotropic. Eight QTL affecting mechanical and morphological traits were detected; two main effects of these QTL were consistently found in all populations and colocated with previously identified dwarfing genes Dw1 and Dw3. These results indicate that dwarfing genes affect the mechanical properties of sorghum stems and their lodging resistance, while also having demonstrable effects on stem morphology. The identification of these QTL provides new opportunities for improving stem lodging resistance via genomics‐assisted breeding.

STRAW STIFFNESS IN LANDRACES OF TWO-ROW BARLEY (HORDEUM VULGARE L.)

This study was aimed to investigate straw stiffness in land races of two- row barley (hordeum vulgarel.). Straw from four landrace populations of barley grown in the Kurdistan Region of Iraq was measured and tested for bending stiffness, showing considerable variation in diameter and in longitudinal bending modulus. In the lower range of diameter, the straw from these landrace populations was highly flexible and was able to lodge without fracture, by curving elastically without fracture or buckling until the head reached the ground. The landrace populations studied contained substantial variation in internode diameter and in the stiffness of the wall material. Selection for internode diameter appeared to have potential for improving lodging resistance. Because lodging potential depends on the weight of the whole shoot as well as on wind forces, it is likely to be increased by pre-harvest moisture content. Decreasing moisture content of the straw and heads reduced the total above-ground weight of the plant by approximately a factor of two during the month prior to harvest.

Proof of concept to unmask the breeding value of genetic resources of barley (Hordeum vulgare) with a hybrid strategy

AbstractBroadening the genetic base of elite breeding programmes is crucial for further breeding success. The absence of major adaption genes, however, often masks the grain yield breeding value of genetic resources. We assessed the ability of a hybrid strategy to provide unbiased performance estimates of 21 barley genetic resources. By crossing them to elite tester lines, 25 three‐way hybrids were produced and evaluated together with a part of their parents and eight elite hybrids for important agronomic traits in replicated field trials in four environments. The phenotypic data analyses revealed that the hybrid strategy facilitated to identify promising resources by substantially improving lodging resistance. Combining genotypic data for 5,562 SNPs with the phenotypic data highlighted the potential to boost the diversity of the elite breeding pool via targeted introgression of genetic resources into the male and female heterotic pools. We propose an application of the hybrid strategy for genetic resources of entire genebank collections and to use genome‐wide predictions to support a targeted choice of accessions with high value for barley breeding.

Semi-dwarf 1 (sd1) gene enhances light penetration into the canopy through regulating leaf inclination angle in rice

Manipulating leaf inclination angle is a feasible approach to improve canopy photosynthesis and dry matter production in rice (Oryza sativa) via enhancing light penetration into the canopy. The importance of the semi-dwarf 1 (sd1) gene, a loss-of-function allele of SD1 encoding GA-20 oxidase-2 in gibberellin (GA) biosynthesis, in rice yield through improving lodging resistance is well known. However, little is known about the effects of sd1 as well as GA on leaf inclination angle. A near-isogenic line carrying the ‘Takanari’ sd1 allele in the ‘Koshihikari’ genetic background (NIL-sd1) had leaves with larger (more erect) leaf inclination angle and showed a smaller canopy extinction coefficient at the ripening stage than did ‘Koshihikari’. Furthermore, the leaf inclination angle of ‘Reimei’, an sd1 mutant in the ‘Fujiminori’ background, and of several other sd1 mutants in ‘Koshihikari’ background, was larger at the ripening stage than in parental lines, ‘Fujiminori’ and ‘Koshihikari’, respectively. The flag leaves of ‘Koshihikari’ plants treated with a GA biosynthesis inhibitor, paclobutrazol (PBZ), displayed a larger leaf inclination angle than did those of mock-treated plants during ripening. Treatment at the lamina joint of a flag leaf with exogenous GA3 or brassinolide (BL) significantly decreased leaf inclination angle. BL treatment increased the thickness of lamina joint tissue and the longitudinal cell length on the adaxial side of the marginal region of lamina joint, whereas GA3 treatment only increased the longitudinal cell length. NIL-sd1 had a lamina joint with decreased longitudinal adaxial cell length, but no difference in abaxial cell length nor tissue thickness in lamina joint cross section compared with that of ‘Koshihikari’. Thus, sd1 regulates the leaf inclination angle via a GA-based mechanism but not via BL involved in the crosstalk with GA.

The mechanical roles of the clasping leaf sheath in cereals: Two case studies from oat and wheat plants

AbstractStem lodging is a common problem in cereal crop production and a main constraint for grain yield improvement. The leaf sheath that surrounds and protects the hollow internodes of stem could provide the plants with a great physical support. However, this biomechanical function has been ignored for several decades in cereal crops. This study aimed to examine the biomechanical properties of basal stem internodes and lodging susceptibility of the whole plants with or without the clasping leaf sheath in wheat (Triticum aestivum L.) and oat (Avena sativa L.) among different genotypes and agronomic practices (including planting densities and nitrogen application rates). The main objective was to quantify the mechanical role of the leaf sheath in oat and wheat crops by a “safety factor” method. On average, the leaf sheath contributed 40%, 68% and 38% of the overall stem bending strength, flexural rigidity and safety factor, in oat, while it accounted for 11%, 24% and 10%, respectively, in wheat plants. The significant contribution of the leaf sheath is due to its vital role in enlarging the peripheral position (i.e., second moment of area) and stiffness (i.e., Young's modulus). The contribution ratios (%) were found to be higher in oat than in wheat plants, due to the greater mass density of leaf sheath and more proficient/prevailing stay‐green capability in oat genotypes. This study emphasizes the important mechanical role of clasping leaf sheath on stem internodes of cereals and indicates that the stay‐green trait of the leaf sheath can be exploited to design appropriate varieties with improved lodging resistance and great yield potential.

Improving Lodging Resistance: Using Wheat and Rice as Classical Examples.

One of the most chronic constraints to crop production is the grain yield reduction near the crop harvest stage by lodging worldwide. This is more prevalent in cereal crops, particularly in wheat and rice. Major factors associated with lodging involve morphological and anatomical traits along with the chemical composition of the stem. These traits have built up the remarkable relationship in wheat and rice genotypes either prone to lodging or displaying lodging resistance. In this review, we have made a comparison of our conceptual perceptions with foregoing published reports and proposed the fundamental controlling techniques that could be practiced to control the devastating effects of lodging stress. The management of lodging stress is, however, reliant on chemical, agronomical, and genetic factors that are reducing the risk of lodging threat in wheat and rice. But, still, there are many questions remain to be answered to elucidate the complex lodging phenomenon, so agronomists, breeders, physiologists, and molecular biologists require further investigation to address this challenging problem.

Rice Homeobox Protein KNAT7 Integrates the Pathways Regulating Cell Expansion and Wall Stiffness.

During growth, plant cells must coordinate cell expansion and cell wall reinforcement by integrating distinct regulatory pathways in concert with intrinsic and external cues. However, the mechanism underpinning this integration is unclear, as few of the regulators that orchestrate cell expansion and wall strengthening have been identified. Here, we report a rice (Oryza sativa) Class II KNOX-like homeobox protein, KNOTTED ARABIDOPSIS THALIANA7 (KNAT7), that interacts with different partners to govern cell expansion and wall thickening. A loss-of-function mutation in KNAT7 enhanced wall mechanical strength and cell expansion, resulting in improved lodging resistance and grain size. Overexpression of KNAT7 gave rise to the opposite phenotypes, with plants having weaker cell walls and smaller grains. Biochemical and gene expression analyses revealed that rice KNAT7 interacts with a secondary wall key regulator, NAC31, and a cell growth master regulator, Growth-Regulating Factor 4 (GRF4). The KNAT7-NAC31 and KNAT7-GRF4 modules suppressed regulatory pathways of cell expansion and wall reinforcement, as we show in internode and panicle development. These modules function in sclerenchyma fiber cells and modulate fiber cell length and wall thickness. Hence, our study uncovers a mechanism for the combined control of cell size and wall strengthening, providing a tool to improve lodging resistance and yield in rice production.

Genetic studies for breeding of rice cultivars with superior grain appearance and lodging resistance from the rice cultivar ‘Emi-no-kizuna’

ABSTRACTWe conducted a quantitative trait locus (QTL) analysis of grain appearance (GA) and agronomic traits of rice, using 128 recombinant inbred lines derived from ‘Emi-no-kizuna’ and ‘Tomohonami’. We detected two promising QTLs associated with GA: qGA4 on chromosome 4 and qGA8 on chromosome 8. qGA4 contributed highly to the greater percentage of perfect grains of the Emi-no-kizuna genotype. In the same region, we detected other QTLs associated with panicle number and spikelet number per panicle. In near-isogenic lines (NILs) in which Emi-no-kizuna alleles were introgressed in the genomic region of only the semi-dwarf 1 (sd1) locus (NIL_1) and both the sd1 locus and qGA8 (NIL_2), respectively, the percentage of perfect grains was significantly higher and the percentages of milky white, basal white, and white back grains were significantly lower than in Tomohonami; and the percentages of milky white and white back grains of NIL_2 were significantly lower than those of NIL_1. These results suggest that introgression in the sd1 region could improve GA, and that the addition of qGA8 could further improve GA. The culm lengths of the NILs were significantly shorter than that of Tomohonami, indicating improved lodging resistance. Grain weight of NIL_2 was significantly smaller than that of NIL_1, suggesting that the effect of qGA8 could be pleiotropic, or the gene that underlies qGA8 could be linked with genes associated with grain weight.Abbreviations: ANOVA: analysis of variance; AT20: mean air temperature in the 20 days after heading; BW: basal white grain; CL: culm length; DAH: days after heading; GA: grain appearance; GW: 1000-grain weight; LOD: logarithm of odds; MW: milky white grain; NIL: near-isogenic line; PG: perfect grain; PL: panicle length; PN: panicle number; PTSN: putative total spikelet number; PVE: percentage of phenotypic variation explained; QTL: quantitative trait locus; RIL: recombinant inbred line; SN: spikelet number per panicle; SNP: single nucleotide polymorphism; WB: white back grain

Identification and characterization of a new dwarf locus DS-4 encoding an Aux/IAA7 protein in Brassica napus

A dominant dwarfing gene, ds - 4 , encodes an Aux/IAA protein that negatively regulates plant stature through an auxin signaling pathway. Dwarfism is an important agronomic trait affecting yield in many crop species. The molecular mechanisms underlying dwarfism in oilseed rape (Brassica napus) are poorly understood, restricting the progress of breeding dwarf varieties in this species. Here, we identified and characterized a new dwarf locus, DS-4, in B. napus. Next-generation sequencing-assisted genetic mapping and candidate gene analysis found that DS-4 encodes a nucleus-targeted auxin/indole-3-acetic acid (Aux/IAA) protein. A substitution (P87L) was found in the highly conserved degron motif of the Aux/IAA7 protein in the ds-4 mutant. This mutation co-segregated with the phenotype of individuals in the BC1F2 population. The P87L substitution was confirmed as the cause of the extreme dwarf phenotype by ectopic expression of the mutant allele BnaC05.iaa7 (equivalent to ds-4) in Arabidopsis. The P87L substitution blocked the interaction of BnaC05.iaa7 with TRANSPORT INHIBITOR RESPONSE 1 in the presence of auxin. The BnaC05.IAA7 gene is highly expressed in the cotyledons, hypocotyls, stems and leaves, but weakly in the roots and seeds of B. napus. Our findings provide new insights into the molecular mechanisms underlying dominant (gain-of-function) dwarfism in B. napus. Our identification of a distinct gene locus controlling plant height may help to improve lodging resistance in oilseed rape.

Mapping of QTLs associated with lodging resistance in rice (Oryza sativa L.) using the recombinant inbred lines derived from two high yielding cultivars, Tachisugata and Hokuriku 193

Lodging is one of the major problems in rice production. In this study, we identified quantitative trait loci (QTLs) for lodging resistance traits using recombinant inbred lines (RILs) derived from a cross between two high yielding and superior lodging resistant rice cultivars, Tachisugata and Hokuriku 193. A total of 19 QTLs were detected on chromosomes (Chrs.) 2, 4, 6, 8, 9 and 10 in the F6 and F7 populations. In particular, one stable QTL for the section modulus (SM) and the outer diameter of the major axis (ODMA) was detected on Chr. 2 in both the F6 and F7 populations, and the positive allele was derived from Tachisugata. Correlation analysis showed that the SM and ODMA were positively correlated with the bending moment at breaking, the primary factor for the breaking type lodging resistance in rice. In addition, two QTLs for the spikelet number of the secondary branch and the spikelet number per panicle were also detected on Chr. 2, which overlapped with the stable QTL for the traits related to lodging resistance. These results indicated that the stable QTL might have combined effects on the traits associated with lodging resistance and grain yield. The novel QTL would be a promising target in marker-assisted selection to improve lodging resistance and grain yield in rice.

High-throughput micro-phenotyping measurements applied to assess stalk lodging in maize (Zea mays L.)

BackgroundThe biomechanical properties of maize stalks largely determine their lodging resistance, which affects crop yield per unit area. However, the quantitative and qualitative relationship between micro-phenotypes and the biomechanics of maize stalks is still under examined. In particular, the roles of the number, geometry, and distribution of vascular bundles of stalks in maize lodging resistance remain unclear. Research on these biomechanical properties will benefit from high-resolution micro-phenotypic image acquisition capabilities, which have been improved by modern X-ray imaging devices such as micro-CT and the development of micro-phenotyping analysis software. Hence, high-throughput image analysis and accurate quantification of anatomical phenotypes of stalks are necessary.ResultsWe have updated VesselParser version 1.0 to version 2.0 and have improved its performance, accuracy, and computation strategies. Anatomical characteristics of the second and third stalk internodes of the cultivars ‘Jingke968’ and ‘Jingdan38’ were analyzed using VesselParser 2.0. The relationships between lodging resistance and anatomical phenotypes of stalks between the two different maize varieties were investigated. The total area of vascular bundles in the peripheral layer, auxiliary axis diameter, and total area of vascular bundles were revealed to have the highest correlation with mechanical properties, and anatomical phenotypes of maize stalk were better predictors of mechanical properties than macro features observed optically from direct measurement, such as diameter and perimeter.ConclusionsThis study demonstrates the utility of VesselParser 2.0 in assessing stalk mechanical properties. The combination of anatomical phenotypes and mechanical behavior research provides unique insights into the problem of stalk lodging, showing that micro phenotypes of vascular bundles are good predictors of maize stalk mechanical properties that may be important indices for the evaluation and identification of the biomechanical properties to improve lodging resistance of future maize varieties.

The Effects of Planting Density on Lodging Resistance, Related Enzyme Activities, and Grain Yield in Different Genotypes of Oilseed Flax

Knowledge of planting density and lodging resistance is essential to developing effective cropping systems. This study determined (i) the lodging resistance of different genotypes of oilseed flax (Linum usitatissimum L.) under different planting densities, and (ii) the effect of density on lignin content and related enzyme activities in different genotypes in Northwest China. We hypothesized that (i) lignin content and related enzyme activities varied with different planting densities, and (ii) a planting density of 750 × 104 grains ha−1 increased the lignin content and related enzyme activities of stem tissues and improved lodging resistance. The characteristics of oilseed flax from three different cultivars—‘Dingya 23’(V1), ‘Jinya 10’(V2), and ‘Neiya 9’(V3)—were evaluated under different planting densities. Results indicated that increasing plant density increased the phenylalanine ammonia‐lyase (PAL) and tyrosine ammonia‐lyase (TAL) activities but decreased the 4‐coumarate:CoA ligase (4CL) activity and lignin content of a high‐lodging‐resistance cultivar. However, increasing plant density decreased the PAL and TAL activities but increased the 4CL and lignin content of a low‐lodging‐resistance cultivar. We conclude that plant density affected the plant lignin content by regulating the 4CL activity. Flax seed yield increases with density were mainly due to increased lignin content, bending strength, and regulated PAL, TAL, and 4CL activities. The study concluded that optimizing planting density could play an important role in crop lodging resistance and grain yields in the northwest of China.

Elevated CO2 improves lodging resistance of rice by changing physicochemical properties of the basal internodes

Elevated atmospheric CO2 concentration has been shown to increase rice yield but its effect on plant lodging resistance is still under debate. In this study, we examined lodging incidence in the field and lodging-related traits of two rice cultivars with contrasting lodging susceptibility under ambient and elevated CO2 (ca. 200 μmol mol−1 above ambient) concentrations by using a free-air CO2 enrichment (FACE) system. Elevated CO2 (E-CO2) increased lodging resistance as shown by reduced visual lodging incidence in the field at the late grain filling stage in E-CO2 plots. This coincided with enhanced in situ pushing resistance of intact plants one week before lodging occurred. The positive CO2 effect was more pronounced in the lodging-susceptible cultivar LY084. In contrast, the cultivar WYJ23 displayed greater pushing resistance in the field, and no lodging occurred at either ambient or elevated CO2 conditions throughout the cropping season. The field observations were consistent with the physicochemical characterization of basal internodes of rice plants at the grain filling stage. Greater lodging-resistance of WYJ23 was mainly attributed to its shorter plant height and thicker culm wall of basal internodes. The improvement of lodging resistance by E-CO2 for the lodging-susceptible cultivar LY084 was mainly related to enhanced culm density, which was explained by elevated starch deposition in the stem. Less lodging incidence under elevated CO2 contributed to an increase in grain yield by 36% for LY084. In conclusion, rice production could benefit from elevated CO2 in a changing climate because of an increase in lodging resistance as a result of CO2-induced improvements in mechanical strength of basal internodes.