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A rice (Oryza sativa L.) semi-dwarf cultivar, Tan-Ginbozu (d35Tan-Ginbozu), contributed to the increase in crop productivity in Japan in the 1950s. Previous studies suggested that the semi-dwarf stature of d35Tan-Ginbozu is caused by a defective early step of gibberellin biosynthesis, which is catalyzed by ent-kaurene oxidase (KO). To study the molecular characteristics of d35Tan-Ginbozu, we isolated 5 KO-like (KOL) genes from the rice genome, which encoded proteins highly homologous to Arabidopsis and pumpkin KOs. The genes (OsKOL1 to 5) were arranged as tandem repeats in the same direction within a 120 kb sequence. Expression analysis revealed that OsKOL2 and OsKOL4 were actively transcribed in various organs, while OsKOL1 and OsKOL5 were expressed only at low levels; OsKOL3 may be a pseudogene. Sequence analysis and complementation experiments demonstrated that OsKOL2 corresponds to D35. Homozygote with null alleles of D35 showed a severe dwarf phenotype; therefore, d35Tan-Ginbozu is a weak allele of D35. Introduction of OsKOL4 into d35Tan-Ginbozu did not rescue its dwarf phenotype, indicating that OsKOL4 is not involved in GA biosynthesis. OsKOL4 and OsKOL5 are likely to take part in phytoalexin biosynthesis, because their expression was promoted by UV irradiation and/or elicitor treatment. Comparing d35Tan-Ginbozu with other high yielding cultivars, we discuss strategies to produce culm architectures suitable for high crop yield by decreasing GA levels.

Knowledge of the changes in physiological traits associated with genetic gains in yield potential is essential to improve understanding of yield-limiting factors and to inform future breeding strategies. Our objective was to identify physiological traits associated with genetic gains in grain yield of winter wheat (Triticum aestivum L.) in the UK. The growth and development of eight representative cultivars introduced from 1972 to 1995 (one tall rht-D1b cultivar and seven Rht-D1b, formerly Rht2, semidwarf cultivars) was examined in field experiments at Sutton Bonington in 1996-1997, 1997-1998, and 1998-1999. A linear genetic gain in grain yield of 0.12 Mg ha(-1) yr(-1) (1.2% yr(-1)) was positively correlated with both harvest index (HI) and aboveground biomass; a quadratic function fitted to the data showed that progress in HI was most apparent during the earlier phase of the 23-yr period, whereas biomass contributed most since about 1983. There was a linear increase across time of 217 grains m(-2) yr(-1), but no change in grain weight. Significant genetic changes across time and correlations with grain yield were also found for preanthesis radiation-use efficiency (RUE, 0.012 g MJ(-1) yr(-1)) and water soluble carbohydrate (WSC) content of stems and leaf sheaths at anthesis (4.6 g m(-2) yr(-1)). Our results suggest that recent genetic gains in grain yield have been based on a combination of improved growth rate in the preanthesis period, which has driven increases in number of grains per square meter, and a larger source for grain filling through increases in stem soluble carbohydrate reserves.

Key messageA 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.

Recent works have demonstrated that plants follow complex decision rules when competing with conspecific neighbours (kin or strangers) and foraging resources. According to kin selection theory, cooperative behaviours toward relatives (i.e. reduced competition) can increase actor’s extended fitness, with advantages to the whole group of relatives. Similarly, several species have reported to adopt different foraging strategies by non-additively integrating information about the presence of neighbours and resource availability in the soil. Here we investigated whether (a) Pisum sativum responds to kin recognition, and (b) kin selection is context dependent. By using two commercial dwarf cultivars in all possible combinations and two levels of nutrients we followed plant growth evaluating their complex behavioural traits. Plants growing with strangers showed increased vegetative biomass production and allocation after 30 days of growth, suggesting an increase of competitive effect. Furthermore, kin selection was stronger in low-resources. Interestingly, at the end of the growth cycle, stranger pairs showed a reduced biomass and fruit production in low resource conditions but not in high nutrition. These results suggest that P. sativum responds selectively to neighbour identity by cooperating with kin neighbours; and they provide evidence that the magnitude of the cooperative response toward kin plants increases as environmental conditions become more stressful.

Background The relatively tall stature of Hedychium limits its application in landscape gardening and pot cultivation while also posing challenges for crop management. Therefore, an in-depth understanding of the regulatory mechanisms controlling plant height is urgently needed to facilitate the development of suitable dwarf cultivars.  Results In this study, HcEXPA4 , a gene that is significantly differentially expressed, was identified in the internode transcriptomes of Hedychium plants with extremely tall and dwarf phenotypes. Sequence alignment revealed that HcEXPA4 is functionally conserved with EXPA4 homologs from other species and is involved in regulating cell elongation. Virus-induced gene silencing (VIGS) of HcEXPA4 resulted in a dwarf phenotype in Hedychium seedlings. Conversely, the overexpression of HcEXPA4 significantly promoted plant height in tobacco. Through correlation analysis and RT‒qPCR, the upstream regulatory transcription factor HcNAC140 was further identified. Silencing HcNAC140 via VIGS notably reduced plant height in Hedychium seedlings and concurrently upregulated the expression of HcEXPA4 . Moreover, the overexpression of HcNAC140 in tobacco led to a significant increase in plant height. The protein interaction assays further confirmed that HcNAC140 specifically binds to the CACG core motif within the HcEXPA4 promoter, directly activating its transcription. Conclusions This study elucidates the pivotal role of the HcNAC140 - HcEXPA4 regulatory module in controlling plant height in Hedychium , providing a theoretical foundation and potential molecular targets for the architectural optimization and molecular breeding of this species.

During the Green Revolution in the 1960s, breeding dwarf cultivars turned out to be a landmark, leading to a significant increase in the global production of wheat and rice. The most direct and effective strategy for breeding dwarf crops, among others, would be to control endogenous gibberellin (GA) levels of the crops. GA 2-oxidases are a group of 2-oxoglutarate-dependent dioxygenases that catalyze the deactivation of bioactive GAs. The ArabidopsisAtGA2ox1 gene was transformed into maize with the aim of obtaining a height-reduced GM maize. The characterization of the GM maize revealed that the highest plant height reduction was accomplished by a 74% decline in GA1 level, and by approximately twofold increases in both chlorophyll content and root/shoot ratio over the wild-type (WT). Interestingly, the stem cells of the GM maize were condensed, and the typical vascular bundle structure was found to be deformed. Based on a 2-season field trial, the GM maize exhibited a higher harvest index (9–17%) and grain yield (10–14%) than the WT. The current results suggest that a modulation of the endogenous GA level would be a sensible approach for improving the crop architecture and grain yield in maize.

Aims Low-vigour scion cultivars and dwarfing rootstocks are a significant contributing factor to the success of modern temperate orchard systems. Planting density and canopy efficiency are currently limited in macadamia by a lack of low-vigour cultivars and rootstocks. The relationships between xylem vessel diameter, hydraulic conductivity and vigour are implicated in dwarf cultivars and low-vigour rootstocks of peach and apple. This study aims to determine relationships between vessel anatomy and tree-scale vigour in subtropical macadamia, to stimulate the development of low vigour cultivars and dwarfing rootstocks. Methods Stem sections from the most recent mature flush were collected from five replicates of three macadamia cultivars: ‘D4’ (high vigour), ‘B25’ (intermediate vigour) and ‘B63’ (low vigour). Sections were imaged under a fluorescence microscope in order to measure the number and size of all xylem vessels in the stem. Results The three cultivars showed distinct differences in height over 5 years of measurement ( P  < 0.001). Change in tree height related to the xylem vessel characteristics of mean vessel area of the ten largest vessels per section (R 2  = 0.57, P  < 0.001), pith size (R 2  = 0.70, P  < 0.001) and total additive vessel area (R 2  = 0.41, P  < 0.01). Conclusions This study indicates that relationships between anatomical structure and vigour in macadamia are likely to be similar to those of well-studied temperate tree crops and that anatomical traits may be useful in the selection of low-vigour cultivars. Future work should investigate hydraulic relationships with vigour and rootstock-scion interactions in macadamia.

Knowledge of changes associated with advances in crop productivity is essential for understanding yield limiting factors and developing strategies for future genetic improvement. The objectives of this study are to understand genetic gain for grain yield and associated traits in the Northern China Winter Wheat Region (NCWWR). Four trials, comprised of 47 leading common wheat (Triticum aestivum L.) cultivars from the NCWWR from 1960 to 2000, were conducted during 2001 to 2003 using a completely randomized block design of three replicates under controlled field environments. Molecular markers were used to detect the presence of dwarfing genes and the 1B/1R translocation. Results showed that average annual genetic gain in grain yield ranged from 32.07 to 72.11 kg ha-1yr-1 or from 0.48 to 1.23% annually in different provinces. The most significant increase in grain yield occurred in the early 1980s, largely because of the successful utilization of dwarfing genes and the 1B/1R translocation. There was no common trend across trials in terms of changes in spikes m-2, kernels per spike, 1000-kernel weight (TKW), or biomass. The genetic improvement in grain yield was primarily attributed to increased grain weight per spike, reduced plant height, and increased harvest index (HI). The dwarfing allele Rht-D1b was the most frequent (68.0%) among the cultivars, followed by Rht 8 (42.0%) and Rht-B1b (16.0%). The frequency of 1B/1R translocation cultivars was 42.6%. The future challenge of wheat breeding in this region is to maintain the genetic gain in grain yield and to improve grain quality, without increasing inputs for the wheat-maize double cropping system.

Based on its compact habit, Micro-Tom, a dwarf cultivar of tomato (Solanum lycopersicum L.), has been proposed as a preferred variety to carry out molecular research in tomato. This cultivar, however, is poorly characterized. It is shown here that Micro-Tom has mutations in the SELF-PRUNING (SP) and DWARF (D) genes. In addition to this, it is also shown that Micro-Tom harbours at least two independently segregating resistance loci to the plant pathogen Cladosporium fulvum. The presence of the self-pruning mutation in Micro-Tom, that generates a determinate phenotype, was confirmed by crossing and sequence analysis. It was also found that Micro-Tom has a mutation in the DWARF gene (d) that leads to mis-splicing and production of at least two shorter mRNAs. The d mutation is predicted to generate truncated DWARF protein. The d sequence defect co-segregates with dark-green and rugose leaves, characteristics of brassinosteroid biosynthesis mutants. Micro-Tom also carries at least another mutation producing internode length reduction that affects plant height but not active gibberellin (GA) levels, which were similar in dwarf and tall Micro-Tom×Severianin segregants. GAs and brassinosteroids act synergistically in Micro-Tom, and the response to GA depends on brassinosteroids because the elongation of internodes was at least six times higher when GA3 was applied simultaneously with brassinolide. A novel variety, Micro-0 that is fully susceptible to C. fulvum and almost as dwarf as Micro-Tom, has been generated from the cross of Cf0×Micro-Tom. This line represents a valuable resource for future analysis of Cf resistance genes through breeding or transformation.

The aim of this review is to check the possibilities and circumstances regarding how to create a high-density Persian walnut orchard. Increasing yields, decreasing tree size, limiting juveniles, and lowering total costs are the most important objectives of breeders and horticulturists. Reducing the size of walnut trees can increase yield. Breeding programs in several countries have led to the production of walnut dwarf rootstocks. For example, Daixiang and Daihui in China, Alvand in Iran, and Fernette in France are all novel-bred dwarfing Persian walnut rootstocks. These precocious walnuts are considered to be a rare resource in the study of precociousness as well as juvenile and flowering mechanisms. Moreover, they play a potential role in breeding and modifying cultivars by genetic engineering, through walnut ameliorating programs. The CRISPR (clustered regularly interspaced short palindromic repeat) technique is used to improve walnuts, which will be used in the near future.