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Comprehensive analysis on investigating water-saving potentials of irrigated cotton in semi-arid area in China
Get PDFDeficit irrigation is a common strategy to reduce water use and improve the sustainability of cotton production. However, the effects of water deficits on crop productivity and quality are subject to genotype by management by environmental interactions. This study investigated effects of water deficits and frequency of irrigation on cotton performance grown in semi-arid region, Xinjiang, the main cotton-growing area in China. Two field trials (2020 and 2021) with split experimental design, including main factors of three irrigation levels (moderate-deficit, mild-deficit and full-irrigation) and split factors of three irrigation frequencies (4, 8 and 12 days) were conducted. Results from two trials both showed little negative influence of irrigation levels on yield, and higher irrigation frequency improved yield under same irrigation level. Significant effects of irrigation levels on yield components were found in 2021, with a 22 % increase in boll number and an 18 % reduction in boll weight under moderate-deficit irrigation compared with those under full-irrigation. Interactions between irrigation levels and frequencies significantly affected harvest index (HI), showing that reduced irrigation might be beneficial for improving HI. However, decreased fibre length while increased fibre micronaire were found under deficit irrigation. A strong association between radiation use efficiency (RUE) and boll growth rate was observed, suggesting that RUE might be the driving force of yield formation. A tight correlation between both biomass and transpiration efficiency versus delta temperature between air and canopy (ΔTair-canopy) was observed, suggesting ΔTair-canopy could be used as an efficient tool to assess plant production under deficit irrigation. This study provided an improved understanding of the physiological basis of cotton yield formation and further identified a high-throughput and instantaneous method to monitor effects of deficit irrigation on crop productivity
Mapping pasture dieback impact and recovery using an aerial imagery time series: a central Queensland case study
Get PDFContext.
Pasture dieback has emerged as a significant threat to the health and productivity of sown pastures in eastern Queensland and northern New South Wales, Australia.
Aims.
We aimed to address knowledge gaps on spatial spread patterns, recovery trajectories and floristic changes using remote sensing and ground surveys.
Methods.
We used a time series of high-resolution (12–25 cm) aerial imagery to quantify and compare pasture dieback spread over 7 years in three land-use areas:
ungrazed pasture, grazed pasture and rehabilitation following mining.
The green leaf index was applied using supervised random forest algorithms to classify areas affected between 2015 and 2021. Flora surveys were conducted to compare impacted and unimpacted areas for the three land uses and validate classifications.
Key results.
The first emergence of pasture dieback was in ungrazed pasture, and these areas recorded the highest rate of dieback spread at 1.88 ha month−1, compared with 0.54 and 0.19 ha month−1 in rehabilitated and grazed pastures respectively. Field validation showed that dieback-impacted pastures shifted from buffel grass (Cenchrus ciliaris L.), to forb-dominated communities with significantly different species mix, biomass and cover conditions. An analysis of local climate data showed that winter night-time temperatures and rainfall were notably higher than long-term means in the year preceding the first detection of pasture dieback.
Conclusions.
High resolution aerial imagery and ground surveys can be used to monitor pasture health by employing vegetation indices and random forest classifiers.
Implications. Ungrazed pastures and roadside areas should be managed to protect the region from further outbreaks
Predicting Carbohydrate Concentrations in Avocado and Macadamia Leaves Using Hyperspectral Imaging with Partial Least Squares Regressions and Artificial Neural Networks
Get PDFCarbohydrate levels are important regulators of the growth and yield of tree crops. Current methods for measuring foliar carbohydrate concentrations are time consuming and laborious, but rapid imaging technologies have emerged with the potential to improve the effectiveness of tree nutrient management. Carbohydrate concentrations were predicted using hyperspectral imaging (400–1000 nm) of leaves of the evergreen tree crops, avocado, and macadamia. Models were developed using partial least squares regression (PLSR) and artificial neural network (ANN) algorithms to predict carbohydrate concentrations. PLSR models had R2 values of 0.51, 0.82, 0.86, and 0.85, and ANN models had R2 values of 0.83, 0.83, 0.78, and 0.86, in predicting starch, sucrose, glucose, and fructose concentrations, respectively, in avocado leaves. PLSR models had R2 values of 0.60, 0.64, 0.91, and 0.95, and ANN models had R2 values of 0.67, 0.82, 0.98, and 0.98, in predicting the same concentrations, respectively, in macadamia leaves. ANN only outperformed PLSR when predicting starch concentrations in avocado leaves and sucrose concentrations in macadamia leaves. Performance differences were possibly associated with nonlinear relationships between carbohydrate concentrations and reflectance values. This study demonstrates that PLSR and ANN models perform well in predicting carbohydrate concentrations in evergreen tree-crop leaves
Genetic diversity of soybean dwarf virus in two regions of mainland Australia
Get PDFSoybean dwarf virus (SbDV; family Tombusviridae, genus Luteovirus, species Luteovirus glycinis) is an RNA plant virus that is transmitted solely by aphids in a persistent, circulative and non-propagative manner. SbDV causes significant losses in cultivated Fabaceae, especially in subterranean clover (Trifolium subterraneum) pastures of mainland Australia. SbDV isolates are classified into four phenotypically distinguishable strains: YP, YS, DP, and DS. Y and D strains differ primarily in their host range, and P and S strains in their primary vector species. Genetically, Y and D strains separate into two clades in every genomic region except for the N-terminal region of the readthrough domain (N-RTD), in which P and S strains separate. SbDV diversity in Australia has yet to be investigated, so in this study, 41 isolates were collected from six different host species across two production regions of Australia: the south coast of Western Australia (‘south-west’) and northern New South Wales/southern Queensland (‘north-east’). A near-complete genome sequence of each isolate was obtained, and together with all 50 whole-genome sequences available in the GenBank database, underwent phylogenetic analysis of the whole genome nt and the N-RTD aa sequences. At the whole-genome level, the isolates separated into D and Y clades. At the N-RTD level, most of the isolates separated into P and S clades. All south-west isolates and 11 of the 31 north-east isolates were in the Y clade, and the remaining 20 north-east isolates were in the D clade. Except for one isolate that fell outside the P and S clades, all south-west and north-east isolates were in the P clade, suggesting that they are transmitted by Acyrthosiphon pisum and Myzus persicae. Available biological data largely supported the phenotypic inferences made from the phylogenetic analysis, suggesting that genetic data can provide critical epidemiological insights, provided that sufficient biological data have been collected
Exploring the cobia (Rachycentron canadum) genome: unveiling putative male heterogametic regions and identification of sex-specific markers
Get PDFCobia (Rachycentron canadum) is the only member of the Rachycentridae family and exhibits considerable sexual dimorphism in growth rate. Sex determination in teleosts has been a long-standing basic biological question, and the molecular mechanisms of sex determination/differentiation in cobia are completely unknown.Here, we reported 2 high-quality, chromosome-level annotated male and female cobia genomes with assembly sizes of 586.51 Mb (contig/scaffold N50: 86.0 kb/24.3 Mb) and 583.88 Mb (79.9 kb/22.5 Mb), respectively. Synteny inference among perciform genomes revealed that cobia and the remora Echeneis naucrates were sister groups. Further, whole-genome resequencing of 31 males and 60 females, genome-wide association study, and sequencing depth analysis identified 3 short male-specific regions within a 10.7-kb continuous genomic region on male chromosome 18, which hinted at an undifferentiated sex chromosome system with a putative XX/XY mode of sex determination in cobia. Importantly, the only 2 genes within/between the male-specific regions, epoxide hydrolase 1 (ephx1, renamed cephx1y) and transcription factor 24 (tcf24, renamed ctcf24y), showed testis-specific/biased gene expression, whereas their counterparts cephx1x and ctf24x, located in female chromosome 18, were similarly expressed in both sexes. In addition, male-specific PCR targeting the cephx1y gene revealed that this genomic feature is conserved in cobia populations from Panama, Brazil, Australia, and Japan.The first comprehensive genomic survey presented here is a valuable resource for future studies on cobia population structure and dynamics, conservation, and evolutionary history. Furthermore, it establishes evidence of putative male heterogametic regions with 2 genes playing a potential role in the sex determination of the species, and it provides further support for the rapid evolution of sex-determining mechanisms in teleost fish
Carbon-to-nitrogen stoichiometry of organic amendments regulates microbial biomass growth and nitrogen mineralization in soil
No full textThe carbon-to-nitrogen (C:N) ratio of organic amendments regulates nutrient cycling in soil through its influence on microbial activity. Where an organic amendment has a C:N ratio sparingly higher than that of soil microbes (C:N ratio 6.7—8.7), meeting microbial requirements of carbon and nitrogen may promote microbial biomass growth and nitrogen mineralization. Here we sought to understand the microbial response to the addition of organic amendments with varying C:N ratios and subsequent changes in nitrogen mineralization and plant nitrogen uptake. Dried insect larvae, beef feedlot manure and mixtures of beef feedlot manure with insect larvae or sugarcane residue were used as soil amendments to create a gradient of molar C:N ratios (Cm:Nm) ranging from 6 to 28. An untreated control treatment with a C:N ratio of 17 was also included. Sorghum (Sorghum bicolor L.) was grown in control and organic matter amended soils for 20 days after germination. The mixture of beef feedlot manure and insect larvae treatment (Cm:Nm = 9.7) had on average 68% higher microbial biomass compared with the other treatments. Beef feedlot manure with Cm:Nm ratio of 11 did not influence microbial biomass growth. The concentration of mineral nitrogen was highest in the insect larvae (Cm:Nm = 6) treatment, where 23% of the plant nitrogen was derived from the insect larvae as indicated by the δ15N of plant dry matter. We observed both carbon and nitrogen contents in the organic amendment determine microbial biomass growth and nitrogen mineralization in soil. The results presented here demonstrate that microbial response to organic amendments determines the availability of mineral nitrogen in soil
Centromeres are hotspots for chromosomal inversions and breeding traits in mango
No full textChromosomal inversions can preserve combinations of favorable alleles by suppressing recombination. Simultaneously, they reduce the effectiveness of purifying selection enabling deleterious alleles to accumulate. This study explores how areas of low recombination, including centromeric regions and chromosomal inversions, contribute to the accumulation of deleterious and favorable loci in 225 Mangifera indica genomes from the Australian Mango Breeding Program. Here, we identify 17 chromosomal inversions that cover 7.7% (29.7 Mb) of the M. indica genome: eight pericentric (inversion includes the centromere) and nine paracentric (inversion is on one arm of the chromosome). Our results show that these large pericentric inversions are accumulating deleterious loci, while the paracentric inversions show deleterious levels above and below the genome wide average. We find that despite their deleterious load, chromosomal inversions contain small effect loci linked to variation in crucial breeding traits. These results indicate that chromosomal inversions have likely facilitated the evolution of key mango breeding traits. Our study has important implications for selective breeding of favorable combinations of alleles in regions of low recombination
Management of glyphosate resistance in summer weeds
No full textIn Australia, glyphosate resistance continues to evolve in both summer and winter weeds and to date, several mechanisms of glyphosate resistance have been identified. Except for Lolium rigidum, each species appears to have a single mechanism across multiple populations. In the key summer weeds Chloris virgata, Conyza bonariensis, Echinochloa colona and Sonchus oleraceus, resistance appears to be conferred by target-site
mutations.
Amino acid substitutions at Proline106 in the EPSPS enzyme, the target of glyphosate, result in resistance, with different amino acid substitutions giving varying levels of resistance both within and across species. The ploidy level of the species can also affect resistance levels, where the effect of a resistance mutation in EPSPS on one subgenome can be diluted by susceptible forms of the gene on other subgenomes. Conversely, multiple subgenomes allow for the accumulation of two or more resistance mutations, leading to increased levels of resistance.
A series of field trials were established in south-east Queensland to measure the effect of different herbicide strategies and resistance mutations on changes in weed density and population genetics. The four summer species mentioned above were included and there were two or three populations of each species, with different glyphosate resistance mechanisms. Treatments were glyphosate alone and as a double knock, an alternative knockdown of 2,4-D or haloxyfop applied alone or as a double knock, and a residual herbicide treatment of either metolachlor or isoxaflutole.
Over three growing seasons, weed control has differed between treatments and followed the same trend for each weed species with control by residual herbicides > alternative double knock > glyphosate double knock > glyphosate alone. Weed seed samples have been collected over the duration of the trials and will be used to quantify the genetic makeup and shift in weed populations over time
Flesh colour as an indicator of total carotenoid concentration and the vitamin A precursor, beta-carotene in mangoes
No full textMangoes (Mangifera indica L.) can vary in flesh colour with it ranging from creamy-yellow to deep orange. The principal flesh pigment in mango is all-trans beta carotene, an orange carotenoid compound. This study reports the impact of the total carotenoid and all-trans beta-carotene concentrations on the final flesh colour of mangoes. A total of 27 cultivars of mangoes were objectively measured for their flesh colour (hue angle and chroma) and their corresponding carotenoid profile were determined using an ultra-high performance liquid chromatography coupled with diode array assay (UHPLC-DAD). It was observed that orange cultivars (low hue angle) tended to have greater total carotenoid concentration and this relationship when plotted demonstrated an exponential decline in carotenoid content as hue angle increased. The chroma also presented an exponential relationship indicating a rise in total carotenoid as the chroma increased, however, a stronger relationship was apparent in the hue angle and total carotenoid. The all-trans beta-carotene also showed similar relationships in both the hue angle and chroma, as it is the principal carotenoid in mangoes. The results of the study showed that the hue angle and chroma has the potential to be an indicator of both the total carotenoid and all-trans beta-carotene concentrations
Fruit Sorting Based on Maturity Reduces Internal Disorders in Vapor Heat-Treated ‘B74’ Mango
No full textPostharvest internal disorders (IDs) in mango fruit present a significant challenge to the industry, with their underlying causes still unclear. This study investigated the relationship between fruit maturity and the susceptibility of vapor heat-treated (VHT) ‘B74’ mangoes to IDs in three experiments. In the first experiment, fruit were categorized into three maturity groups based on dry matter content (DMC): 17%, using a handheld near-infrared device. Half of the fruit in each group underwent VHT, while the remainder were untreated controls. Flesh cavity with white patches (FCWP) was the only disorder observed exclusively in VHT fruit. The incidence and severity of FCWP was significantly higher (p < 0.05) in fruit with <15% DMC, with 12.4% incidence and a severity score of 0.2 on a 0–3 scale (0: healthy and 3: severely affected), compared to more mature fruit. In the second experiment, the fruits were harvested at early and late maturity stages, with average DMC values of 14.5% and 17.4%, respectively. The fruit was subjected to no VHT, VHT, and VHT following a 12 h pre-conditioning period at 37 ± 1 °C. Consistent with the first experiment, FCWP was observed only in VHT fruit, with early-harvested fruit displaying a significantly higher (p < 0.05) FCWP incidence (26.9%) and severity (0.3) compared to late-harvested fruit (8.3% incidence and 0.1 severity). Pre-conditioning significantly reduced FCWP, particularly in early-harvested fruit. In the third experiment, fruit maturity sorted based on density was assessed, followed by VHT and simulated sea freight under controlled (CA) and ambient atmospheres. Fruit density did not effectively differentiate maturity considering DMC as a maturity indicator. Storage conditions significantly reduced (p < 0.05) flesh browning incidence from 71.1% under ambient conditions to 33.3% under CA. This study highlights fruit maturity as a key factor in the susceptibility of ‘B74’ mangoes to postharvest IDs following VHT. Therefore, sorting fruit based on DMC at harvest or at the packing facility prior to VHT serves as a valuable decision support for reducing IDs in VHT fruit. Further research will explore advanced technologies to enable rapid and efficient fruit sorting based on DMC