Dwarf Lines Research Articles

Additional Advantages for Agronomic Performance and Fruit Quality in Tomato Hybrids of the Saladette Type Derived from a Dwarf Male Parent

Tomatoes have tremendous economic, social, and nutritional importance. Among the various types of tomatoes, the Saladette/Italian stands out as an important cultivar for both fresh consumption and industrial processing. The production of this vegetable requires investments exceeding USD 30,000.00. Strategies that increase productivity to offset these costs are fundamental. One proposal to increase yield potential in tomato is the production of new hybrids using dwarf male parents as donors through an organized backcross breeding scheme. The present study, therefore, evaluated possible improvements in the agronomic performance and fruit quality of Saladette hybrids obtained from crosses between normal and dwarf inbred lines. Seventeen tomato hybrids obtained from three backcrosses (BC1, BC2, and BC3) and two commercial cultivars as a control (cv. Bento and Vivacy) were evaluated. The data were analyzed using the Scott–Knott test, and artificial neural networks were used to study the dissimilarities among the hybrids. The hybrids obtained from the dwarf male parent exhibited morphological changes in the plants, including a reduction in internodes, a greater number of bunches per linear meter of plant, and biofortification of the fruits. Notably, from the second backcross onwards, increases in fruit productivity and quality were observed when creating hybrid combinations from dwarf male parents.

The inheritance pattern for the dwarf phenotype in hybrids from crosses among sunflower lines differing in alleles of the Rht1 locus

Background. Sunflower seed production is based on utilization of the heterosis effect, manifesting itself in improving both yield and plant height in hybrids. Short-stemmed lines need to be used to develop commercial hybrids with an optimum height. Molecular bases of the trait manifestation in the dwarf lines from VIR’s sunflower genetic collection have not yet been studied. Materials and methods. The material included 27 short-stemmed and 10 tall sunflower lines from VIR’s genetic collection, as well as the F1 and F2 hybrid generations derived from crossing the tall (VIR 340) and dwarf (VIR 171) genotypes. The parental lines and hybrids were phenotyped for plant height, leaf number, and internode length. Genotyping for the Rht1 locus (HaDella1 candidate gene), encoding the negative regulator of the gibberellin response, the DELLA protein, was performed using the developed CAPS marker. Results. The average plant height in the VIR 340 line over a three-year study was 162 cm, the number of leaves 29, and the internode length 6 cm. The VIR 171 line demonstrated the plant height of 66 cm, leaf number of 24, and internode length of 2.8 cm. The F1 hybrids were uniform, with the height of 180–190 cm, that indicated the dominance of the long stem trait. Analyzing the segregation in the F2 hybrid generation led to an assumption admitting the digenic control of the dwarf phenotype in the VIR 171 line. The CAPS marker G-D-1/ Bmt I was developed to identify a missense mutation T>C in the first exon of the HaDella1 gene, which results in the substitution of leucine with proline in the DELLA motif. Using the marker, the mutant Rht1 allele was identified in the VIR 171 and VIR 434 dwarf lines, similar in their origin and phenotype. The results of validation in the F2 hybrid population (VIR 340 × VIR 171) confirmed the efficiency of the G-D-1 / Bmt I marker for selecting dwarf genotypes homozygous for the Rht1 mutant allele.

Analysis of the Candidate Genes and Underlying Molecular Mechanism of P198, an RNAi-Related Dwarf and Sterile Line.

The genome-wide long hairpin RNA interference (lhRNAi) library is an important resource for plant gene function research. Molecularly characterizing lhRNAi mutant lines is crucial for identifying candidate genes associated with corresponding phenotypes. In this study, a dwarf and sterile line named P198 was screened from the Brassica napus (B. napus) RNAi library. Three different methods confirmed that eight copies of T-DNA are present in the P198 genome. However, only four insertion positions were identified in three chromosomes using fusion primer and nested integrated polymerase chain reaction. Therefore, the T-DNA insertion sites and copy number were further investigated using Oxford Nanopore Technologies (ONT) sequencing, and it was found that at least seven copies of T-DNA were inserted into three insertion sites. Based on the obtained T-DNA insertion sites and hairpin RNA (hpRNA) cassette sequences, three candidate genes related to the P198 phenotype were identified. Furthermore, the potential differentially expressed genes and pathways involved in the dwarfism and sterility phenotype of P198 were investigated by RNA-seq. These results demonstrate the advantage of applying ONT sequencing to investigate the molecular characteristics of transgenic lines and expand our understanding of the complex molecular mechanism of dwarfism and male sterility in B. napus.

Repression of GhTUBB1 Reduces Plant Height in Gossypium hirsutum.

The original 'Green Revolution' genes are associated with gibberellin deficiency. However, in some species, mutations in these genes cause pleiotropic phenotypes, preventing their application in dwarf breeding. The development of novel genotypes with reduced plant height will resolve this problem. In a previous study, we obtained two dwarf lines, L28 and L30, by introducing the Ammopiptanthus mongolicus (Maxim. ex Kom.) Cheng f. C-repeat-binding factor 1 (AmCBF1) into the upland cotton variety R15. We found that Gossypium hirsutum Tubulin beta-1 (GhTUBB1) was downregulated in L28 and L30, which suggested that this gene may have contributed to the dwarf phenotype of L28 and L30. Here, we tested this hypothesis by silencing GhTUBB1 expression in R15 and found that decreased expression resulted in a dwarf phenotype. Interestingly, we found that repressing AmCBF1 expression in L28 and L30 partly recovered the expression of GhTUBB1. Thus, AmCBF1 expression presented a negative relationship with GhTUBB1 expression in L28 and L30. Moreover, yeast one-hybrid and dual-luciferase assays suggest that AmCBF1 negatively regulates GhTUBB1 expression by directly binding to C-repeat/dehydration-responsive (CRT/DRE) elements in the GhTUBB1 promoter, potentially explaining the dwarf phenotypes of L28 and L30. This study elucidates the regulation of GhTUBB1 expression by AmCBF1 and suggests that GhTUBB1 may be a new target gene for breeding dwarf and compact cultivars.

CRISPR/Cas9 genome-editing applied to MdPGT1 in apple results in reduced foliar phloridzin without impacting plant growth.

Phloridzin is the most abundant polyphenolic compound in apple (Malus ×domestica Borkh.), which results from the action of a key phloretin-specific UDP-2'-O-glucosyltransferase (MdPGT1). Here, we simultaneously assessed the effects of targeting MdPGT1 by conventional transgenesis and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated genome editing. To this end, we conducted transcriptomic and metabolic analyses of MdPGT1 RNA interference knockdown and genome-edited lines. Knockdown lines exhibited characteristic impairment of plant growth and leaf morphology, whereas genome-edited lines exhibited normal growth despite reduced foliar phloridzin. RNA-sequencing analysis identified a common core of regulated genes, involved in phenylpropanoid and flavonoid pathways. However, we identified genes and processes differentially modulated in stunted and genome-edited lines, including key transcription factors and genes involved in phytohormone signalling. Therefore, we conducted a phytohormone profiling to obtain insight into their role in the phenotypes observed. We found that salicylic and jasmonic acid were increased in dwarf lines, whereas auxin and ABA showed no correlation with the growth phenotype. Furthermore, bioactive brassinosteroids were commonly up-regulated, whereas gibberellin GA4 was distinctively altered, showing a sharp decrease in RNA interference knockdown lines. Expression analysis by reverse transcriptase-quantitative polymerase chain reaction expression analysis further confirmed transcriptional regulation of key factors involved in brassinosteroid and gibberellin interaction. These findings suggest that a differential modulation of phytohormones may be involved in the contrasting effects on growth following phloridzin reduction. The present study also illustrates how CRISPR/Cas9 genome editing can be applied to dissect the contribution of genes involved in phloridzin biosynthesis in apple.

Inheritance of dwarfism and narrow lobed-leaf in two rapeseed (Brassica napus L.) mutant lines

There is a need for dwarf and narrow lobed-leaves rapeseed cultivars to reduce transpiration under drought prone areas. A dwarf mutant line ‘H2M-1’ and a mutant with reduced lobed-leaf ‘H2M-2’ were developed. To exploit these mutated traits properly in an effective breeding program, one should understand their mode of inheritance. There are conflicting findings for plant dwarfism and limited studies for leaf size in mutant genetic backgrounds. Therefore, the objective of this study was to investigate the inheritance of dwarfism and narrow lobed-leaf mutated traits. Plants of the wild-type variety ‘INRA-CZH2’ were reciprocally crossed with plants of the line ‘H2M-1’ and plants of the line ‘H2M-2’. A genetic study was conducted by analyzing segregation of mutated traits in F1, F2 and BC1F1 generations. The results revealed that two recessive genes with dominant epistasis action controlled the heredity of plant height in the dwarf line, whereas only a single recessive gene is involved in determining reduced lobed-leaf in the line H2M-2. Thus, there is a possibility to easily and quickly transfer these characters into rapeseed breeding germplasm or varieties towards the development of suitable cultivars for areas marked by increasing drought stress.

Agronomic potential of BC1F2 populations of Santa Cruz dwarf tomato plants

The use of dwarf lines to obtain mini-tomato hybrid plants has led to agronomic and economic advantages. However, the benefits provided by dwarf parents in tomato hybrids of the Santa Cruz type remain unexplored. The aims of this study were to determine the agronomic enhancement in BC1F2 dwarf populations bearing characteristic fruit of the Santa Cruz type after the first backcross and to select populations with high agronomic potential and fruit quality. The experiment was conducted in a greenhouse using a randomized block design with 15 treatments and 4 replicates. Evaluated genetic materials included 11 BC1F2 dwarf tomato populations, both parents (recurrent and donor), and the cultivars (Santa Cruz Kada and Santa Clara). Traits evaluated included: mean weight, soluble solid concentration, number of locules, shape, pulp thickness, fruit longitudinal and transversal diameters, internode length, and plant height. Univariate, multivariate, correlation, and selection index analyses showed that mean fruit weight, transverse diameter, and pulp thickness increased significantly in dwarf populations after a single backcross, most of them exhibiting a fruit shape similar to that of the Santa Cruz type. The dwarf BC1F2 populations UFU-Sci#11 and UFU-Sci#12 showed high potential for obtaining lines and, subsequently, Santa Cruz type hybrids.

Alternative Splicing (AS) Dynamics in Dwarf Soybean Derived from Cross of Glycine max and Glycine soja

Short crop height is the preferred breeding trait since there is a positive correlation between lodging resistance and a crop yield increase. Alternative splicing can alter transcriptome diversity and contribute to plant adaptation to environmental stress. We characterized the transcriptomes obtained from dwarf and normal soybean lines derived from a cross of Glycine max var. Peking (G. max) and G. soja var. IT182936 in an F7 RIL population to study the differences between the isoforms. Full-length mRNA derived from leaf tissues was sequenced using the PacBio RSII platform, generating 904,474 circular consensus sequence (CCS) reads. Using the Structural and Quality Annotation of Novel Transcript Isoforms (SQANTI) process, 42,582 and 44,762 high-quality isoforms, and 91 and 179 polished low-quality isoforms were obtained in dwarf and normal cells, respectively. As a result, 832 and 36,772 nonredundant transcripts were generated. Approximately 30% of the identified genes were estimated to produce two or more isoforms. We detected an average of 166,171 splice junctions (SJs), of which 93.8% were canonical SJs. We identified that novel isoforms accounted for 19% of all isoforms, among which 12% fell within coding regions. The dwarf soybean demonstrated a greater number of isoforms in most of the annotated genes, particularly in genes related to growth hormones and defense responses. Our study provides comprehensive isoform and gene information that may accelerate transcriptome research in G. max and provide a basis to further study the impact of these isoforms on plant growth.

Comparing the structural characteristics and expression of GA2ox gene in dwarf banana and its wild type

It is necessary to understand the molecular mechanism of banana dwarfing mutation in order to improve the high stem character of banana varieties and breed the new excellent dwarf lines. To elucidate the molecular-level regulation of banana dwarf mutations and identify the relevant genes, the complete cDNA sequence of the gibberellin 2-oxidase gene (GA2ox) in the dwarf banana and its wild type was cloned by RT-PCR and the encoded amino acid sequences bioinformatically was analyzed. Meanwhile, the expression levels of banana GA2ox gene in different tissues of dwarfed banana and its wild type were analyzed by qRT-PCR. Between the GA2ox gene sequences of the dwarf banana and its wildtype, there were 5 base pairs of variation, leading to the predicted GA2ox proteins having different molecular weights, isoelectric points, fat indices, total numbers of positive and negative charges, and hydrophilicity. In addition, the expression of GA2ox in the leaves, stalks, and fruits of dwarf banana plants was higher than that in the wild type in the early and middle stages of banana development. The results showed that the GA2ox gene may have important regulatory effects on banana stem dwarfing, the knowledge of which can help our understanding and manipulation of this important plant.

AmCBF1 Transcription Factor Regulates Plant Architecture by Repressing GhPP2C1 or GhPP2C2 in Gossypium hirsutum.

Dwarfism is a beneficial trait in many crops. Dwarf crops hold certain advantages over taller crops in lodging resistance, fertilizer tolerance, and yield. Overexpression of CBF/DREB transcription factors can lead to dwarfing in many plant species, but the molecular mechanism of plant dwarfing caused by overexpression of CBF/DREB in upland cotton (Gossypium hirsutum) remains unclear. In this study, we observed that overexpression of the Ammopiptanthus mongolicus AmCBF1 transcription factor in upland cotton R15 reduced plant height, whereas virus-induced gene silencing of AmCBF1 in the derived dwarf lines L28 and L30 partially restored plant height. Five protein phosphatase (PP2C) genes (GhPP2C1 to GhPP2C5) in cotton were identified by RNA-sequencing among genes differentially expressed in L28 or L30 in comparison with R15 and thus may play an important role in AmCBF1-regulated dwarfing in cotton. Gene expression analysis showed that the GhPP2C genes were down-regulated significantly in L28 and L30, and silencing of GhPP2C1 or GhPP2C2 in R15 inhibited the growth of cotton seedlings. Subcellular localization assays revealed that GhPP2C1 was localized to the cell membrane and nucleus, whereas GhPP2C2 was exclusively localized to the nucleus. Yeast one-hybrid and dual-luciferase assays showed that AmCBF1 was able to bind to the CRT/DRE elements of the upstream promoter of GhPP2C1 or GhPP2C2 and repress their expression. These findings provide insight into the mechanism of dwarfing and may contribute to the breeding of dwarf cultivars of upland cotton.

Wheat dwarf genes Rht12 and Rht‐B1b affected the performance of agronomic traits in hexaploid triticale

AbstractAs a new synthetic species, triticale has been widely used for food and feed. Lodging is a severe problem in triticale production, and it is unknown whether wheat height‐reducing genes can improve lodging resistance in triticale. In this study, the wheat‐dwarfing genes Rht12 and Rht‐B1b were introgressed into hexaploid triticale (AABBRR) lines to understand their effect on plant height. The results showed that Rht12 and Rht‐B1b reduced the plant height of triticale plants by 37.7 and 29.9%, respectively. Rht12 and Rht‐B1b both had significant effects on the basal internode's length, diameter, and thickness, which may greatly improve lodging resistance. Additionally, the net photosynthetic rate was increased by 28.7% in Rht12 dwarf lines. However, Rht12 had a significant and negative effect on thousand‐kernel weight (14.5%) and yield per plant (20.6%). On the other hand, Rht‐B1b reduced the number of tillers by 19.6% and yield per plant by 18.1% with no negative effect on the harvest index. Furthermore, Rht12 and Rht‐B1b decreased grain plumpness but improved several grain quality traits. Conclusively, Rht12 and Rht‐B1b improved lodging resistance but had some negative effects on yield components, which need careful consideration in triticale breeding.

The fine mapping of dwarf gene Rht5 in bread wheat and its effects on plant height and main agronomic traits.

Rht5 was narrowed to an approximately 1Mb interval and had pleiotropic effects on plant height, spike length and grain size. TraesCS3B02G025600 was predicted as the possible candidate gene. Plant height is an important component related to plant architecture, lodging resistance, and yield performance. The utilization of dwarf genes has made great contributions to wheat breeding and production. In this study, two F2 populations derived from the crosses of Jinmai47 and Ningchun45 with Marfed M were employed to identify the genetic region of reduce plant height 5 (Rht5), and their derived lines were used to evaluate its effects on plant height and main agronomic traits. Rht5 was fine-mapped between markers Kasp-25 and Kasp-23, in approximately 1Mb region on chromosome 3BS, which harbored 17 high-confidence annotated genes based on the reference genome of Chinese Spring (IWGSC RefSeq v1.1). TraesCS3B02G025600 were predicted as the possible candidate gene based on its differential expression and sequence variation between dwarf and tall lines and parents. The results of phenotypic evaluation showed that Rht5 had pleiotropic effects on plant height, spike length, culm diameter, grain size and grain yield. The plant height of Rht5 dwarf lines was reduced by an average of 32.67% (32.53cm) and 27.84% (33.62cm) in the Jinmai47 and Ningchun45 population, respectively. While Rht5 showed significant and negative pleiotropic effects on culm diameter, aboveground biomass, grain yield, spike length, spikelet number, grain number per spike, grain size, grain weight and filling degree of basal second internode. The culm lodging resistance index (CLRI) of dwarf lines was significantly higher than that of tall lines in the two population. In conclusion, these results lay a foundation for understanding the dwarfing mechanism of Rht5.

The exogenous GA3 greatly affected the grain-filling process of semi-dwarf gene Rht4 in bread wheat.

Rht4 is characterized as a GA-responsive dwarf gene in bread wheat (Triticum aestivum L.). The responsiveness of Rht4 to exogenous GA3 was characterized in seedlings, but the effects of exogenous GA3 on the important morphological and agronomic traits such as plant height, grain-filling rate, and yield components are unclear. In this study, the Rht4 responsiveness of exogenous GA3 on these traits was evaluated using the homozygous F4:5 and F5:6 lines derived from a cross between Jinmai47 and Burt ert937 (Rht4 donor). After exogenous GA3 application, the plant height of the dwarf lines was, on average, increased by 17.54%, about 7.92% more than that of the tall lines. Compared with the tall lines, application of exogenous GA3 significantly increased the kernel weight, maximum grain-filling rate (Gmax), average grain-filling rate (Gave) and kernel weight increment achieving Gmax (Wmax) in both superior and inferior grains, while the day on which the maximum grain-filling rate was reached (Tmax) in Rht4 dwarf lines was significantly earlier in the two generations. What is more, the grain number spike-1 , grain yield plant-1 , and 1000-kernel weight (TKW) of the dwarf lines notably increased after exogenous GA3 -treatment, while there was no significant change in the tall lines except for TKW. The quality traits of the dwarf lines with GA3 -treatment were greatly improved. Taken together, these results suggested that the application of GA3 could improve the grain-filling process of Rht4 and compensate for some negative influences, which may provide a reference for its application in wheat breeding and promote the characterization of its regulatory mechanisms.

The effect of the Rht1 haplotype on Fusarium head blight resistance in relation to type and level of background resistance and in combination with Fhb1 and Qfhs.ifa-5A

Key messageThe effect of the Rht1-genes on FHB resistance depends on anther extrusion and level of background resistance. Qfhs.ifa-5A increases resistance and anther extrusion as efficiently as semi-dwarfing alleles decrease it.The semi-dwarfing reduced height alleles Rht-D1b and Rht-B1b have been deployed in modern wheat cultivars throughout the world, but they increase susceptibility to Fusarium head blight (FHB). Here, we investigated the impact of the Rht1 genes on anther retention (AR) in relation to FHB resistance using four different sets of near-isogenic lines (NILs) with contrasting levels and types of background FHB resistance. NILs were evaluated for FHB severity, plant height and AR in three greenhouse and three field trials using artificial spray inoculation. Rht-B1b and Rht-D1b alleles increased AR and FHB susceptibility in all genetic backgrounds. The magnitude of the effects differed between NIL groups. Increased FHB susceptibility largely followed increased AR. Differences in FHB susceptibility between tall and dwarf haplotypes were largest in the NIL group with the highest changes in AR. In the most resistant NIL group, dwarfed lines had only slightly higher AR than tall lines and maintained good resistance, while both tall and dwarf lines had high levels of retained anthers in the most susceptible NIL group. We further investigated the effect of the major Fusarium resistance QTL Fhb1 and Qfhs.ifa-5A in combination with the Rht1 genes. Qfhs.ifa-5A enhanced anther extrusion in tall as well as semi-dwarf haplotypes, whereas Fhb1 did not affect AR. Qfhs.ifa-5A supported FHB resistance more efficiently than Fhb1 in lines that were more responsive to AR, while both Fhb1 and Qfhs.ifa-5A were equally efficient in NILs that had high background resistance and low response to AR.

Fine mapping and candidate gene analysis of dwarf gene Rht14 in durum wheat (Triticum durum).

Semi-dwarf and dwarf genes were widely used in wheat breeding for improving lodging resistant and increasing yield. Rht14 dwarf gene was identified and deployed in durum wheat, where it showed advantage on important agronomic potential. The reciprocal F2 populations derived of Castelporziano (CP) and Langdon (L) were used for mapping of Rht14, which was located in intervals 4.8cM and 10.38cM by KASP (Kompetitive Allele Specific PCR) markers, respectively, where corresponding to 312-454 Mbp on chromosome 6A, and finally, it was mapped to the genomic region of 402 ~ 408 Mbp in Durum Wheat Svevo RefSeq Rel. 1.0 (i.e., 405 ~ 411 Mbp in Chinese Spring RefSeq v.1.0) using recombinants by indel markers. The expression of TdGA2oxA9 was higher in dwarf line than tall lines and the bioactive GA1 was lower. No sequence difference was observed in the promoter and coding region of GA2oxA9 between the dwarf and tall parent, while obvious DNA methylation difference was found in its promoter. Two methylation-related genes with high confidence located in the candidate region and expressed differently between the tall and dwarf ones. This study proposed that Rht14 might regulate the expression of GA2oxA9 by DNA methylation in its promoter, which provided a way to clone Rht14 and to further investigate the mechanism behind.

Characterization and potential utilization of recently available milk thistle, Silybum marianum (L.) Gaertn., wild type and mutant accessions

AbstractMilk thistle, Silybum marianum (L.) Gaertn. (Asteraceae), is an economically important medicinal plant utilized for silymarin production. Moreover, the species has been positively evaluated for vegetable oil and biomass production. Despite these positive characteristics, milk thistle is still marked by traits that are typical of undomesticated species (most importantly natural fruit dispersal at maturity) and requires further genetic improvement for its complete exploitation. This manuscript summarizes all the information collected through time about a collection of nine milk thistle wild and mutant lines and it discusses the possible further utilization of these genotypes. The accessions are characterized by interesting traits related to: fruit silymarin composition (S. marianum chemotype A and B), fruit fatty acid composition (high oleic and high stearic acid lines), fruit condensed tannins content, vegetative biomass composition (modification of xylans or lignin content), vegetative biomass structure (dwarf and tall lines), modifications of leaf variegation (hypervareigated line) and different types of fruit shatter resistance at maturity. All the lines underwent subsequent generations of selfing and are stable for all the described traits. The accessions will be made available at the Genebank of the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK, Gatersleben) and may prove to be a useful genetic material for the improvement of qualitative fruit traits (silymarin quality, fatty acid composition) and for the further development of shatter-resistant S. marianum genotypes towards the complete domestication of this promising species.

Transgenic rice plants expressing the α-L-arabinofuranosidase of Coprinopsis cinerea exhibit strong dwarfism and markedly enhanced tillering.

Lignocellulosic materials are potential renewable sources of fermentable sugars for bioethanol production. In this study, we used the CcAbf62A gene encoding CcAbf62A, a putative extracellular α-L-arabinofuranosidase, cloned from the mycotrophic basidiomycete Coprinopsis cinerea. CcAbf62A acts on arabinoxylan, the major hemicellulose of grasses, releasing arabinose. CcAbf62A was introduced into rice with the aim of enhancing delignification efficiency and the availability of lignocellulosic materials without reducing lignin content. Among the 32 lines of regenerated transgenic rice, 13 exhibited markedly disrupted elongation growth and excessive tillering (dwarf), seven showed delayed elongation growth (retarded-growth), and 12 showed phenotypes similar to those of control plants (normal). Additionally, the dwarf lines showed reduced acclimation. RT-PCR analysis revealed that dwarf lines had higher levels of CcAbf62A expression than retarded-growth and normal lines. Although the lignin content of transgenic rice plants expressing CcAbf62A did not differ significantly from that of control rice plants, dwarf lines were characterized by delayed deposition of lignin in the culms compared with the controls. The reduced acclimation ability of dwarf lines is believed to be associated with increased water loss and reduced water conductivity concomitant with delayed lignin deposition. Contrary to expectations, the alkaline delignification rates of dwarf and retarded-growth Abf lines were slightly lower than those of control rice plants. Our findings indicate that CcAbf62A reduces ferulate-lignin cross-links by detaching arabinose side chains from arabinoxylan and increases the relative abundance of alkaline-resistant benzyl ether cross-links. CcAbf62A is anticipated to provide new approaches for breeding plants containing altered lignocellulosic materials or lodging-resistant crops.

Physiology and whole-plant carbon partitioning during stem sugar accumulation in sweet dwarf sorghum.

A greater rate of phloem unloading and storage in the stem, not a higher rate of sugar production by photosynthesis or sugar export from leaves, is the main factor that results in sugar accumulation in sweet dwarf sorghum compared to grain sorghum. At maturity, the stem internodes of sweet sorghum varieties accumulate high concentrations of fermentable sugars and represent an efficient feedstock for bioethanol production. Although stem sugar accumulation is a heritable trait, additional factors that drive sugar accumulation in sorghum have not been identified. To identify the constraints on stem sugar accumulation in sweet sorghum, we used a combination of carbon-11 (11C) radiotracer, physiological and biochemical approaches, and compared a grain sorghum and sweet dwarf sorghum line that have similar growth characteristics including height. Photosynthesis did not increase during development or differ between the sorghum lines. During the developmental transition to the reproductive stage, export of 11C from leaves approximately doubled in both sorghum lines, but 11C export in the sweet dwarf line did not exceed that of the grain sorghum. Defoliation to manipulate relative sink demand did not result in increased photosynthetic rates, indicating that the combined accumulation of C by all sink tissues was limited by the maximum photosynthetic capacity of source leaves. Nearly 3/4 of the 11C exported from leaves was transported to the lower stem in sweet sorghum within 2h, whereas in grain sorghum nearly 3/4 of the 11C was in the panicle. Accordingly, the transcripts of several sucrose transporter (SUT) genes were more abundant in the stem internodes of the sweet dwarf line compared to the grain sorghum. Overall, these results indicate that sugar accumulation in sweet sorghum stems is influenced by the interplay of different sink tissues for the same sugars, but is likely driven by elevated sugar phloem unloading and uptake capacity in mature stem internodes.

Analysis of genome variants in dwarf soybean lines obtained in F6 derived from cross of normal parents (cultivated and wild soybean).

Plant height is an important component of plant architecture and significantly affects crop breeding practices and yield. We studied DNA variations derived from F5 recombinant inbred lines (RILs) with 96.8% homozygous genotypes. Here, we report DNA variations between the normal and dwarf members of four lines harvested from a single seed parent in an F6 RIL population derived from a cross between Glycine max var. Peking and Glycine soja IT182936. Whole genome sequencing was carried out, and the DNA variations in the whole genome were compared between the normal and dwarf samples. We found a large number of DNA variations in both the dwarf and semi-dwarf lines, with one single nucleotide polymorphism (SNP) per at least 3.68 kb in the dwarf lines and 1 SNP per 11.13 kb of the whole genome. This value is 2.18 times higher than the expected DNA variation in the F6 population. A total of 186 SNPs and 241 SNPs were discovered in the coding regions of the dwarf lines 1282 and 1303, respectively, and we discovered 33 homogeneous nonsynonymous SNPs that occurred at the same loci in each set of dwarf and normal soybean. Of them, five SNPs were in the same positions between lines 1282 and 1303. Our results provide important information for improving our understanding of the genetics of soybean plant height and crop breeding. These polymorphisms could be useful genetic resources for plant breeders, geneticists, and biologists for future molecular biology and breeding projects.

Elite sd1 alleles in japonica rice and their breeding applications in northeast China

The Green Revolution gene sd1 has been used extensively in modern rice breeding, especially in indica cultivars. However, elite sd1 alleles and related germplasm resources used for japonica rice breeding have not been identified, and extensive efforts are needed for japonica rice breeding to obtain new dwarfing sources. Data from MBKbase-Rice revealed seven sd1 haplotypes in indica and four in japonica rice. Two new sd1 alleles were identified in indica rice. In 295 japonica accessions from northeast Asia, except for the weak functional allele SD1-EQ, sd1-r was the major allele, reducing plant height in comparison with SD1-EQ. Japonica germplasm resources carrying reported sd1 alleles were identified by genotype searching and further verified by literature search, genealogical analysis, and dCaps markers. Pedigrees and geographic distribution showed that sd1-r is an excellent allele widely used in northern China and Tohoku in Japan, and sd1-j is commonly used in east China and Kyushu in Japan. Dongnong- and Xiushui-series cultivars carrying sd1-r and sd1-j, respectively, are essential branches of the backbone parents of Chinese japonica rice, Akihikari and Ce21, with the largest number of descendants and derived generations. In semi-dwarf japonica rice breeding, sd1-d was introgressed into Daohuaxiang 2 (DHX2). Dwarf and semi-dwarf lines carrying sd1-d were selected and designated as 1279 and 1280, respectively, after withstanding typhoon-induced strong winds and heavy rains in 2020, and are anticipated to become useful intermediate materials for future genetic research and breeding. This work will facilitate the introduction, parental selection, and marker-assisted breeding, and provide a material basis for the next step in identifying favorable genes that selected together with the sd1 alleles in japonica backbone parents.