Coleoptile Length Research Articles

Codium fragile (Suringar) Hariot as Biostimulant Agent to Alleviate Salt Stress in Durum Wheat: Preliminary Results from Germination Trials.

Soil salinization is a critical environmental problem in arid and semiarid regions of the world. The aim of the present study was to evaluate the effect of an algae-based biostimulant on germination and seedling vigour of durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.), under different saline conditions (0, 100, and 200 mM NaCl). The experiment was carried out under controlled-environment conditions. Seeds were sprayed with a solution containing a combination of fungicide and different concentrations of Codium fragile (Suringar) Hariot algae (0%w/v, 10%w/v, 20%w/v, and 30%w/v). All experimental units were placed in a germination cabinet. The effect of the seaweed extract (SWE) on seed germination and seedling performance under salinity stress was evaluated over a period of 8 days. Coleoptile length and biomass were found to be significantly and positively affected by the application of different SWE doses as compared to the control treatment (0% algae). As for germination traits, seeds treated with SWE showed a final germination (from 82% to 88%), under severe saline conditions, significantly higher than that observed in the control treatment (61%). Our findings indicate that the appropriate dose of biostimulant can markedly improve the germination and the seedlings vigour of durum wheat seeds under saline conditions. Additional studies will be needed to understand the mechanism of action of this biostimulant and its effectiveness in longer studies under field conditions.

Development and validation of diagnostic markers for the reduced height gene Rht8 in wheat

AbstractWheat (Triticum aestivum L.) production is necessary for global food and nutrition security. Reducing plant height is an effective strategy to increase lodging resistance, harvest index, and eventually wheat yield. Rht8 is a gibberellic acid–sensitive reduced height (Rht) gene and has been cloned. Rht8 encodes a ribonuclease H‐like (RNHL) superfamily protein that reduces plant height without reduction in coleoptile length. High‐throughput diagnostic markers are not available for precise selection of RNHL in wheat breeding. In this study, we found that different cultivars may carry 1–3 copies of RNHLs on chromosome 2D, and only 2D carries the semi‐dwarf allele of RNHL although the wild‐type RNHL allele is detected in several other chromosomes. We developed two kompetitive allele specific PCR (KASP) markers, Rht8‐KASP‐V2 and Rht8‐KASP‐V3, based on the causal variation in RNHL. The two markers co‐segregated with plant height in a recombinant inbred population and were validated in a panel of hard winter wheat breeding lines from the 2022 Regional Germplasm Observation Nursery and Regional Performance Nursery. Rht8 has not been extensively deployed in US hard winter wheat and development of the diagnostic KASP markers will facilitate Rht8 transfer to US wheat cultivars.

Effect of Allelochemicals from Cereal Rye Cultivar and Pythium lutarium on Corn Growth and Disease

Allelopathic chemicals produced by a cereal rye (CR; Secale cereale L.) cover crop have been implicated in the negative effect of CR on corn planted into decomposing CR residue. Production of allelochemicals varies among CR cultivars. In the current study, the allelopathic effect of crude extracts from five CR cultivars (Elbon, Hazlet, Serafino, Tayo, and Yankee) was evaluated on corn seedling growth, mycelial growth of Pythium lutarium, and root rot of corn caused by P. lutarium using a plate assay. In general, crude extracts from all CR cultivars slowed pathogen growth and reduced corn coleoptile and radicle lengths. When corn was grown on media amended with crude extracts from the CR cultivars and colonized with P. lutarium, corn growth was reduced and root rot severity increased compared with the check (no extract with pathogen). Subsequently, a cup assay was used to further investigate the allelopathic effect of Elbon, Hazlet, and Serafino on corn seedling growth and root rot. Corn grown in cups into which each cultivar had been planted had shorter radicles and coleoptiles compared with the check (no CR), regardless of the CR cultivar. Results from this study suggest that allelochemicals released from decomposing CR vary among cultivars, and their interaction with Pythium spp. could affect seedling disease on corn. Consequently, choice of CR cultivar may be an important management decision to reduce the negative effects of CR on corn. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Genome‐wide association analysis of coleoptile length and interaction with plant height in durum wheat

AbstractGenotypes with longer coleoptiles can be sown in deep soil layers to reach the underground moisture needed for germination in dry areas. Developing new varieties with longer coleoptiles and shorter plant heights would be novel for wheat breeding and production. In this study, coleoptile lengths of a panel of durum wheat (Triticum turgidum ssp. durum) genotypes were determined, and 14,255 DArTseq (SNP and Silico‐DArT) markers were used to identify coleoptile length‐associated markers by genome‐wide association study (GWAS). A wide genetic variation was accounted for both coleoptile length and plant height. The genetic relationships between coleoptile length and plant height were evaluated using plant height values from five different environments. Two environmentally stable MTAs were identified, one for coleoptile length (QCol.su.4BS) and one for plant height (QPh.su.4BS). These MTAs were located on the short arm of chromosome 4B, with LOD scores up to 12.00 and 17.00, respectively. A relatively high LD (r2 = 0.71) was accounted for between QCol.su.4BS and QPh.su.4BS. The LD block intervals of the MTAs overlapped with some genes with roles in plant growth and development. The functions of plausible candidate genes tell us that QCol.su.4BS may be controlling coleoptile length, whereas QPh.su.4BS may be regulating plant height. The combination of the two loci would be desirable. In conclusion, this study sheds light on the genetic control of coleoptile length and its relationship with plant height in durum wheat.

Resistance selection of local sorghum varieties in East Nusa Tenggara, Indonesia against Rhizoctonia solani

Abstract. Feni EI, Kasmiyati S, Meitiniarti VI. 2023. Resistance selection of local sorghum varieties in East Nusa Tenggara, Indonesia against Rhizoctonia solani. Biodiversitas 24: 5309-5318. Sorghum is a multifunctional crop that can be used as an alternative food for the people of East Nusa Tenggara. However, one of the challenges in cultivating sorghum in this region is the presence of the Rhizoctonia solani pathogen. This fungus causes a devastating root rot disease in sorghum crops, resulting in loss of crop yields and potentially disrupting food security in the region. Using resistant varieties is one of the most effective ways to prevent the growth of R. solani biologically. Therefore, it is important to study the resistance of local sorghum varieties. The purpose of this study was to determine different sorghum varieties' resistance responses to the R. solani fungus that causes root rot disease. This study used a completely randomized design (CRD) with 2 levels of treatment: the treatment of sorghum varieties and the treatment of fungi inoculums, which were inoculated separately and simultaneously. Each treatment was repeated 3 times. Observations and data collection were carried out on the 7th day, and some of the parameters observed included germination percentage, radicle length, coleoptile length, sprout length, GTI value, and disease incidence value. The sorghum variety with the highest resistance value was found in the red variety. This red variety had a disease incidence value of 63.3%, much lower than the other four test varieties. These results provide important insights for developing a more root rot disease-resistant local sorghum plant variety.

The interactions of Rht15 and Rht1 alleviate some of their negative effects on agronomic traits in durum wheat

The application of dwarfing genes in wheat breeding effectively reduced plant height, improved lodging resistance and increased the harvest index. Although the gibberellin-responsive (GAR) dwarf gene Rht15 did not negatively affect coleoptile length or root traits while reducing the plant height, it reduced the yield plant−1. The gibberellin-insensitive (GAI) dwarf gene Rht1 can increase wheat yield under favorable conditions, but it reduces coleoptile length and affects root traits. This study was conducted to investigate whether the interaction of Rht15 and Rht1 can alleviate their negative effects. To analyze the interaction of Rht15 and Rht1, field experiments were conducted with the F5, F6 and F7 lines of the four genotypes, Rht15+Rht1, Rht15, Rht1 and tall lines detected using Rht15 and Rht1 molecular markers, derived from Durox (Rht15) and Kronos (Rht1), by comparing their effects on seedling traits, plant height and internode length, lodging resistance, flag leaf, yield and quality traits in durum wheat. The results showed that although the interaction of Rht15 and Rht1 did not overcome the inhibitory effect of Rht1 on coleoptile growth, it alleviated the negative effect of Rht1 on maximum root length (+14.8%). The grain yield plant−1 (+7.2%) of the Rht15 lines was improved under the action of Rht1 but was still lower than that of the Rht1 lines (−12.7%). The Rht15+Rht1 lines had the strongest effect on reducing plant height and center of gravity height (−42.2% and −41.5%), which significantly improved lodging resistance (+175%). The flag leaf area (+97.4%) and SPAD value (+11.6%, +9.6% and +10.6%) were also significantly increased. In addition, the coleoptile length of the Rht15 lines was not significantly different from that of the tall lines, the plant height and center of gravity height were significantly reduced (−30.5% and −34.0%), and the lodging resistance was significantly increased (+176.8%). The Rht1 lines had increased grain yield (+12.7%) due to an increased 1000-kernel weight (+12.9%) compared to the tall lines. In conclusion, the combination of Rht15 and Rht1 alleles enhanced the advantages and partially alleviated the defects in some traits when compared to the individual alleles, but the grain yield plant−1 was still lower than the Rht1 lines. This reflected the limitations of Rht15, and further confirmed the yield advantages of Rht1.

Efektivitas Priming pada Benih Jagung dalam Memperbaiki Perkecambahan pada Media Masam

The high Aluminum content in Ultisol soil is one of the main problems in maize cultivation starting from the germination phase to plant growth. Priming treatment on seeds is believed to be able to improve germination in a less favorable environment. The study was conducted to determine the effect of priming on the germination of corn seeds germinated in acid media containing aluminum. The study was arranged in a Completely Randomized Design (CRD) which was repeated four times. There were 8 treatments in this study, namely control/without priming, water priming, KNO3 0.1%, and 0.5, PEG-6000 5% and 10%, GA3 50 ppm and 100 ppm. The data were analyzed for variance and continued with a 5% LSD test using the R Studio statistic program. The results showed that 50 ppm GA3 priming was the best treatment for increasing corn seed vigor based on the variables of time of radicle emergence, time of emergence of plumules, growth speed, growth synchronously, vigor index, root length, coleoptile length, wet weight of normal sprouts, and dry weight of normal sprouts. Keywords:priming, corn, germination

Characterization of Rice (Oryza sativa L.) Germplasm for Early Seedling Vigour-related Traits under Direct Seeded Condition

In pursuit of boosting rice production while maintaining economic feasibility within resource constraints, the shift from the traditional puddled-transplanted rice system to direct-seeded rice is gaining significance. Early seedling vigour (ESV) is an important character crucial for direct-seeded rice to outcompete and suppress weed growth. This study evaluated hundred rice germplasm accessions for their early seedling vigour-related traits. Mesocotyl and coleoptile lengths, chlorophyll content, alpha-amylase, speed of emergence, shoot and root characteristics, and vigour indices exhibited notable variability as indicated by their high PCV and GCV. Moreover, they were predominantly under the influence of additive gene effects, as illustrated by their high heritability and genetic advance as per cent of mean. This suggests that these traits are heritable and could be effectively exploited through selective breeding efforts. Positive correlations were found between seedling vigour and traits like emergence (%), speed of emergence, chlorophyll content, and alpha-amylase activity. Based on PCA, Vigour index-I, II, total seedling length, and chlorophyll contents were regarded as major discriminators in rice germplasm for direct seeded traits. The superior genotypes for seedling vigour such as Honduras and Gharib, could be used as donors in the rice breeding programs to develop direct seeded rice cultivars.

The influence of water-soluble secretions of saffron seed on the germination of seeds of soft winter wheat varieties

Due to climate change, there is a need to introduce new crops into agricultural production in Ukraine, among which Crocus sativus L., a herbaceous perennial tuberous plant, whose allopathic properties have been insufficiently studied, can take a leading place. Therefore, the aim of the study was to determine the effect of water-soluble flower secretions and their individual elements on the initial stages of seed germination of two winter durum wheat varieties (Vidrada and Koshova). In the course of the study, generally accepted methods were used: laboratory research, analysis, synthesis and statistical. It was found that water-soluble extracts of flowers of different states and elements of C. sativus flowers do not have a significant effect on the morphometric and quality parameters of wheat kernels during germination. Water-soluble secretions of flowers of different states have an inhibitory effect on the development of the root system; secretions of the bud and the bloomed flower inhibit the growth of coleoptiles. The effect of water-soluble secretions of sowing saffron flowers elements has varietal peculiarities: for winter wheat seedlings of Vidrada variety, the petals have a stimulating effect on the total length of roots and their weight; for seedlings of Koshova variety, the opposite effect is observed. The water-soluble secretions of petals and stamens have a stimulating effect on the coleoptile of Vidrada plants, and the water-soluble secretions of petals have a stimulating effect on Koshova seedlings. The correlation between the length of roots and coleoptile under the influence of watersoluble secretions of flowers of different states and their elements, as well as the index of allelopathy have varietal characteristics. The obtained scientific results will contribute to the development of agrotechnical measures for the cultivation of saffron in Ukraine, selection of winter wheat varieties for joint cultivation and use of plant residues as biological stimulants

Effect of Embryo Weight and Seed Priming on Seedling Characteristics of Different Maize Cultvars

An laboratory experiment was carried out during the year 2020 at the Seed Technology Laboratory of the Crop Department - College of Agricultural Engineering Sciences - University of Baghdad in order to know the effect of seed priming and size of their embryos of different cultivars of maize on the seedling characteristics. The experiment was carried out in a completely randomized design with four replicates. The first factor included three synthetic cultivars of maize (Al-Maha, Baghdad 3 and Al-Fajr) and Al-Nahrain hybrid. For the second factor, it included the priming of seeds with ASA, CK, GA3, KCL, H2O2, DW and DS, in addition to the dry seeds (without priming). The seeds were soaked with solutions of these substances for 24 hours and six characteristics related to the germination process were estimated, which were the weight of the seed after stimulation, the weight of the embryo, the time of germination, the length of the radicle and shoot, and its dry weight. The results showed that the seed priming with H2O2 was significantly superior, as it gave the highest average of seed weight, lowest average germination time, longest average radiclelength and highest seedling dry weight (0.336 g, 3.12 days, 15.08 cm and 0.215 g, respectively). The treatment of seeds with ascorbic was superior in giving the highest average weight of the embryo that reached 0.049 gm, the treatment of stimulating the seeds with gibberellin was superior in giving the highest mean of the coleoptile length of 10.79 cm. Al-Maha cultivar excelled in giving it the highest average seed weight, embryo weight, radiclelength and dry weight, as it reached 0.335 g, 0.050 g, 14.42 cm and 0.194 g, respectively. Whereas, the Fajr cultivar was significantly superior by giving the highest average coleoptile length of 9.37 cm. The interaction effect between the study factors was significant in most of the studied traits.

Genomic landscape of the OsTPP7 gene in its haplotype diversity and association with anaerobic germination tolerance in rice.

Early season flooding is a major constraint in direct-seeded rice, as rice genotypes vary in their coleoptile length during anoxia. Trehalose-6-phosphate phosphatase 7 (OsTPP7, Os09g0369400) has been identified as the genetic determinant for anaerobic germination (AG) and coleoptile elongation during flooding. We evaluated the coleoptile length of a diverse rice panel under normal and flooded conditions and investigated the Korean rice collection of 475 accessions to understand its genetic variation, population genetics, evolutionary relationships, and haplotypes in the OsTPP7 gene. Most accessions displayed enhanced flooded coleoptile lengths, with the temperate japonica ecotype exhibiting the highest average values for normal and flooded conditions. Positive Tajima's D values in indica, admixture, and tropical japonica ecotypes suggested balancing selection or population expansion. Haplotype analysis revealed 18 haplotypes, with three in cultivated accessions, 13 in the wild type, and two in both. Hap_1 was found mostly in japonica, while Hap-2 and Hap_3 were more prevalent in indica accessions. Further phenotypic performance of major haplotypes showed significant differences in flooded coleoptile length, flooding tolerance index, and shoot length between Hap_1 and Hap_2/3. These findings could be valuable for future selective rice breeding and the development of efficient haplotype-based breeding strategies for improving flood tolerance.

Pengaruh Bahan Pelleting terhadap Perkecambahan Benih Bawang Merah (Allium cepa L.)

Shallot is an important commodity, but their productivity in Indonesia is still low. TSS can be used because of its higher production, longer shelf life, more resistance to disease pathogens, cheaper procurement and distribution costs, guaranteed seed quality, and high productivity potential, but has a small shape so it is difficult to plant so seed coating technology is needed. Seed pellets are coatings of seeds to change the shape, size and weight of seeds. This study aims to determine the effect of pelleting techniques on shallot seeds. This research was conducted with one treatment factor, namely without pelleting, soil + CMC, soil + CMC + Mycorrhizae, soil + CMC + Trichoderma, soil + CMC + Dolomite, soil + CMC + humic acid, soil + AG, soil + AG+ Mycorrhizae, soil +AG+Trichoderma, soil+AG+Dolomite, soil+AG+Humic acid. Each treatment was carried out with 3 replications so that 33 experimental units were obtained, with one experimental unit in the form of a planting media tray with 25 seeds each. The results of the study explained that the pelleting technique had no effect on germination, root length, coleoptile length, wet safe weight, dry safe weight, seed weight and had a significant effect on the emergence of plumules with the best treatment obtained in the soil. CMC + humic acid and seed pellet weight. stated that seed pellets can change the weight, size and shape of seeds so as to facilitate planting. The conclusion of this study is that shallot seed pelleting can be applied to shallot cultivation because it does not inhibit the growth and development of shallots and can facilitate the planting of shallot seeds. Key words: Shallot, seed, pelleting, TSS

Screening of Anaerobic Germination Rice Genotypes in Nepal

Poor germination has been the main obstacles to the widespread adoption of rainfed lowland rice production due to the saturated state of the soil, . In order to produce rice types appropriate for direct seeded culture, the current experiment was conducted to find rice with anaerobic germination tolerance. The screening techniques of the tray method were used to assess the anaerobic germination tolerance of 402 different rice genotypes. Under anaerobic conditions, the genotypes 10 genotypes namely, IR 129077:1-1-6-8-B, IR 129077:1-1-6-9-B, IR 129077:2-1-16-8-B, IR 129077:1-1-36-5-B, IR 129077:1-1-41-7-B, IR 129077:1-1-46-6-B, IR 129077:2-1-17-6-B, IR 129077:1-1-31-5-B, IR 129077:1-1-39-8-B, IR 129077:2-1-13-7-B, IR 129077:2-1-17-7-B and IR 129077:2-1-28-7-B recorded the highest germination percentages (> 80%). Under anaerobic germination, the recorded coleoptile length for all genotypes ranged from 0.50 to 10.6 cm. The best performing genotypes were chosen for genotyping using previously published SSR markers based on the screening results. On QTL analysis, anaerobic germination QTL (qAG) present on Chromosome number 11 and chromosome 12 for higher germination and QTL (qCL) on chromosome 12 for longer coleoptile. Int. J. Appl. Sci. Biotechnol. Vol 11(2): 78-84.

Evaluation of twenty genotypes of wheat (Triticum aestivum L.) grown under heat stress during germination stage

Heat stress is one of the most devastating abiotic stresses which causes significant loss of agricultural crop productivity. Thus, it is critical to examine the wheat’s response to the heat stress at seedling stage and adopt an appreciated breeding method to develop heat tolerance and to avoid harmful effects. Therefore, twenty wheat genotypes, including two local landraces, were evaluated in the current study to investigate the genetic diversity for heat tolerance at the seedling stage. Grains of wheat genotypes were placed on filter papers in Petri dishes for germinating at different temperature ranges (i.e., 25 °C as control, 30 °C, 35 °C, and 40 °C). The experiment was laid out in a completely randomized design (CRD) with the factorial arrangement and the number of replications was three. Analysis of variance (ANOVA) for seedling traits and biochemical analysis showed that the genotypes had significant differences for coleoptile length, shoot length (SL), root length (RL), shoot fresh weight (SFW), vigor index (VI), glycine betaine (GB) and proline content. The effect of temperature treatments on different wheat genotypes also exhibited highly significant variation for VI. Principal component analysis (PCA) showed that four factors contributed 82.8% to total variability with the Eigen value greater than 0.7 at 35 °C. Correlation analysis showed that coleoptile length and germination percentage (GP) had a highly significant-positive correlation with SL, VI, and SFW. Results showed that wheat genotypes of ‘Maraj’, ‘Fareed’, ‘Darabi’, ‘Zincol-16’, ‘Barsat’, ‘NARC-2011’, and ‘Mundar’ showed superior performance when grown under different temperatures. ‘NARC-2011’, ‘Inqalab-91’, and ‘Galexy’ wheat genotypes performed well regarding of H2O2 and antioxidant activity. These genotypes had a significant level of variability under heat stress and can be used under high temperatures in future breeding programs for further research purposes.

PHYSIOLOGICAL RESPONSE OF SOME WHEAT CULTIVARS TO THERMAL STRESS

Plants are exposed during their development to the influence of various stressful factors, both abiotic and biotic in natural conditions of habitation. Thermal stress is likely the most important abiotic factor that adversely affects plant growth and development. Wheat (Triticum aestivum L.) is one of the most economically important crops worldwide. In this study, three Latvian winter wheat cultivars ´Creator´, ´Galerist´, and ´Skagen´ were used as a research model that were subjected to short-term high temperature (42°C, 1 h) and analyzed for the following growth parameters (maximum length of root, length of first leaf and coleoptile as well as seedlings weight). In general, short-term high temperature caused an insignificant reduction in almost all growth criteria like the first leaf growth, coleoptile growth, seedlings weight, and maximal root growth in wheat cultivars ´Skagen´ and ´Galerist´ at the 6th day of development. Furthermore, almost all growth characteristics were stimulated by short-term high temperature in the wheat cultivar ´Creator´. A slowing of the growth processes under the influence of short-term thermal stress revealed varietal specificity on the impact of this stressor on the morphological structure of cereal, which makes it possible to diagnose the stress tolerance of wheat cultivars.

Lysinibacillus spp.: an IAA-producing endospore forming-bacteria that promotes plant growth

Lysinibacillus is a bacterial genus that has generated recent interest for its biotechnological potential in agriculture. Strains belonging to this group are recognized for their mosquitocidal and bioremediation activity. However, in recent years some reports indicate its importance as plant growth promoting rhizobacteria (PGPR). This research sought to provide evidence of the PGP activity of Lysinibacillus spp. and the role of the indole-3-acetic acid (IAA) production associated with this activity. Twelve Lysinibacillus spp. strains were evaluated under greenhouse conditions, six of which increased the biomass and root architecture of corn plants. In most cases, growth stimulation was evident at 108 CFU/mL inoculum concentration. All strains produced IAA with high variation between them (20–70 µg/mL). The bioinformatic identification of predicted genes associated with IAA production allowed the detection of the indole pyruvic acid pathway to synthesize IAA in all strains; additionally, genes for a tryptamine pathway were detected in two strains. Extracellular filtrates from all strain’s cultures increased the corn coleoptile length in an IAA-similar concentration pattern, which demonstrates the filtrates had an auxin-like effect on plant tissue. Five of the six strains that previously showed PGPR activity in corn also promoted the growth of Arabidopsis thaliana (col 0). These strains induced changes in root architecture of Arabidopsis mutant plants (aux1-7/axr4-2), the partial reversion of mutant phenotype indicated the role of IAA on plant growth. This work provided solid evidence of the association of Lysinibacillus spp. IAA production with their PGP activity, which constitutes a new approach for this genus. These elements contribute to the biotechnological exploration of this bacterial genus for agricultural biotechnology.

Wheat plant height locus RHT25 encodes a PLATZ transcription factor that interacts with DELLA (RHT1)

Plant height is an important agronomic trait with a significant impact on grain yield, as demonstrated by the positive effect of the REDUCED HEIGHT (RHT) dwarfing alleles (Rht1b) on lodging and harvest index in the "Green Revolution" wheat varieties. However, these gibberellic acid (GA)-insensitive alleles also reduce coleoptile length, biomass production, and yield potential in some environments, triggering the search for alternative GA-sensitive dwarfing genes. Here we report the identification, validation, and characterization of the gene underlying the GA-sensitive dwarfing locus RHT25 in wheat. This gene, designated as PLATZ-A1 (TraesCS6A02G156600), is expressed mainly in the elongating stem and developing spike and encodes a plant-specific AT-rich sequence- and zinc-binding protein (PLATZ). Natural and induced loss-of-function mutations in PLATZ-A1 reduce plant height and its overexpression increases plant height, demonstrating that PLATZ-A1 is the causative gene of RHT25. PLATZ-A1 and RHT1 show a significant genetic interaction on plant height, and their encoded proteins interact with each other in yeast and wheat protoplasts. These results suggest that PLATZ1 can modulate the effect of DELLA on wheat plant height. We identified four natural truncation mutations and one promoter insertion in PLATZ-A1 that are more frequent in modern varieties than in landraces, suggesting positive selection during wheat breeding. These mutations can be used to fine-tune wheat plant height and, in combination with other GA-sensitive dwarfing genes, to replace the GA-insensitive Rht1b alleles and search for grain yield improvements beyond those of the Green Revolution varieties.

Long coleoptile genotype and soil texture interactions determine establishment success and early growth parameters of wheat sown at depth

Long coleoptile (LC) - wheat genotypes sown deeper (> 10 cm) than current practice (< 5 cm) enables earlier deep sowing into subsurface soil moisture. The LC genotype shows promise to broaden sowing windows and remove reliance on the shifting seasonal break for crop establishment. The suitability of this sowing strategy to the highly variable soils of the southern Australian wheatbelt warrants investigation to identify suitable environments for potential establishment benefits. We conducted controlled environment room (CER) and field experiments using pairs of near-isogenic-lines (NILs) that differed genetically only for coleoptile length. The experiments investigated the suitability of deep sown (12 cm) LC wheats in soils with different texture (sand versus loam). The CER experiment identified that LC genotypes exhibited greater emergence and early seedling growth, producing greater shoot and root biomass, when deep sown (12 cm) in loam. While LC and short coleoptile (SC) genotypes produced similar shoot growth when sown at depth in sand, LC produced greater root biomass reflected in more seminal roots. In the field on sand, LC and SC had similar emergence and early shoot growth characteristics at all sowing depths (5, 8 and 10 cm). However, the heavy-textured, loam soil reduced seedling emergence and restricted leaf growth with deep sowing (12 cm) in the SC. Our results indicate that the LC trait was more critical for plant emergence and early growth parameters (shoot and root biomass) from depth in a heavier textured loam compared with a sand. By identifying environments that will likely benefit most from deep sown LC, we are one step closer to adapting crop production to shifting rainfall patterns in southern Australia.

UDP-glucosyltransferase OsUGT75A promotes submergence tolerance during rice seed germination

Submergence stress represents a major obstacle limiting the application of direct seeding in rice cultivation. Under flooding conditions, coleoptile elongation can function as an escape strategy that contributes to submergence tolerance during seed germination in rice; however, the underlying molecular bases have yet to be fully determined. Herein, we report that natural variation of rice coleoptile length subjected to submergence is determined by the glucosyltransferase encoding gene OsUGT75A. OsUGT75A regulates coleoptile length via decreasing free abscisic acid (ABA) and jasmonic acid (JA) levels by promoting glycosylation of these two phytohormones under submergence. Moreover, we find that OsUGT75A accelerates coleoptile length through mediating the interactions between JASMONATE ZIMDOMAIN (OsJAZ) and ABSCISIC ACID-INSENSITIVE (OsABI) proteins. Last, we reveal the origin of the haplotype that contributes to coleoptile length in response to submergence and transferring this haplotype to indica rice can enhance coleoptile length in submergence conditions. Thus, we propose that OsUGT75A is a useful target in breeding of rice varieties suitable for direct seeding cultivation.

The Impact of Carbohydrate Management on Coleoptile Elongation in Anaerobically Germinating Seeds of Rice (Oryza sativa L.) under Light and Dark Cycles

The ability of rice to elongate coleoptiles under oxygen deprivation is a determinant of anaerobic germination tolerance, critical for successful direct seeding. Most studies on anaerobic coleoptile elongation have been performed under constant darkness or in flooded soils because a drilling method was the primary approach for direct seeding of rice. However, aerial seeding is becoming popular, in which seeds which land on flooded soils are exposed to light during the daytime. Here, we investigated physiological mechanisms underlying anaerobic elongation of coleoptiles under light and dark cycles. This study identified two novel varieties, LG and L202, enabling the development of long coleoptiles under oxygen limitation, comparable to well-characterized varieties with strong anaerobic germination tolerance. Germination experiments using these two tolerant and two intolerant varieties, including Takanari and IR64, revealed that light and dark cycles increased coleoptile length in LG, Takanari, and IR64 relative to constant darkness. Interestingly, even in intolerant lines, dramatic starch breakdown and soluble carbohydrate accumulation occurred under oxygen limitation. However, intolerant lines were more susceptible to a representative soluble sugar, glucose, than tolerant lines under oxygen deprivation, suggesting that coleoptile growth can be inhibited in intolerant lines due to hypersensitivity to soluble sugars accumulated in anaerobically germinating seeds.