Wendy Vance

Chickpea has become an increasingly popular healthy food worldwide. Aluminum (Al) toxicity is a major hurdle for chickpea cultivation and yield improvement in acidic soils. However, the genetic mechanism of Al-tolerance in chickpea remains poorly understood. Here, we performed a large-scale hydroponics screening and SNP chip array genotyping of 1154 diverse chickpea accessions. Root lengths after 6 days cultivation under hydroponics in control (T0: pH 4.2) and Al treatment (T1: pH4.2, 15/20 μM Al3+) were measured. Root tolerance index (RTI = T1/T0) ranking revealed significant variations in chickpea Al-tolerance, with common Australian chickpea cultivars positioned in the low to medium range. Genome-wide association analyses revealed eight QTLs on chromosomes ca1 (CaAlt1-1), ca3 (CaAlt3-1), ca4 (CaAlt4-1, CaAlt4-2), ca5(CaAlt5-1), ca6 (CaAlt6-1), and ca7 (CaAlt7-1, CaAlt7-2) associated with T1, implying a multigenic genetic basis for Al-tolerance in chickpea. Specifically, CaAlt7-2 was associated with both T1 and RTI, whilst CaAlt4-2 was detected for T1 uniquely in the HatTrick x CudiB22C population. Al- tolerant and sensitive haplotypes for the identified QTLs were also identified. Organic acid transporter genes CaMATE2, CaMATE4, and CaALMT1 were found in proximal genomic regions to CaAlt7-2, CaAlt4-1, and CaAlt6-1, respectively. Further qRT-PCR in parental chickpea lines (HatTrick, Slasher, Gunas, CudiB) confirmed that CaMATE2 and CaMATE4 were strongly induced upon Al treatment. Interestingly, CaMATE2 was preferentially expressed in the upper part of the root, whilst CaMATE4 preferentially in the root tips, implying a potential complementary role in Al resistance. Their direct roles in Al tolerance and the potential alternative candidate genes near the QTLs require further investigation. This first report of QTLs on Al-tolerance in chickpea has substantially advanced our understanding of the genetic basis of Al tolerance in chickpea and will facilitate the rapid breeding of Al-tolerant chickpea cultivars for previously un-accessible acidic soils.

Aims
Production of high yielding forage grasses on the extensive areas of tropical sandy soils in the Lower Mekong Basin is constrained by acidity, low soil nutrient concentrations, and potassium and sulfur depletion, limiting the ability of rural households in the region to meet the economic opportunities arising from the growing demand for livestock products in Asia. This research aimed to measure the response of forages grown in sandy soils that were provided with additional potassium sulfur, and lime inputs. It was hypothesized that additional potassium, sulfur and lime above local recommendations would increase biomass production and soil organic carbon concentrations.

Methods
An experiment was conducted over two years in the Lao PDR to compare the response and soil organic carbon accumulation of forage grasses grown in sandy soils that were either managed according to recommended fertilizer and manure additions, or provided with additional potassium and sulfur at four different rates, and lime.

Results
Yield increases of 25% were achieved with additional K and S but benefits were conditional on season and variety. Soil organic carbon concentration in the top 5 cm increased by up to 1.38 t ha−1 with forage production.

Conclusions
High yielding forages are likely to become limited by soil potassium. The imbalance of supplied nitrogen relative to potassium highlights inefficiencies in the recommended rates relative to forage production requirements, demonstrating potential to improve productivity and reduce nitrogenous waste. Increases in organic carbon stocks indicate the potential for improved forages to provide environment benefits.

Phenotype and genotype data collected from the GRDC-funded project UMU2303-003RTX (Developing genetic tools to facilitate breeder use and deployment of high value acid soils tolerant chickpea germplasm). The genotype data consisted of approximately 4,300 high-quality SNP markers of 520 chickpea accessions. The phenotype data, including the tolerance index, plant growth data and yield-related traits, were collected from multiple trials across Australia from 2023 to 2025.

The extent to which Conservation Agriculture (CA) practices alter nitrogen (N) balance in intensive rice-based cropping systems of the Eastern Indo-Gangetic Plain was examined, focusing on a legume dominated-system (LDS) and a cereal dominated-system (CDS) in north-west Bangladesh. Three crop establishment methods were imposed—strip planting (SP) and bed planting (BP) for non rice crops with non-puddled rice establishment; compared with conventional tillage (CT) for non rice crops along with puddled transplanting of rice. Two levels of crop residue retention were superimposed—high (HR) and low (LR - conventional farm practice) crop residue retention. The CA practices (SP and non-puddled rice with HR) increased total soil N concentrations, and the soil N-stocks at 0–0.075 m over CT and LR in both CDS and LDS sites after 2.5 years. At 0–0.15 m soil depth, total soil N concentrations increased over time under SP and BP, but decreased with CT. In LDS, annual soil N increase (65 kg N ha −1 ) occurred with SP while negligible N losses were observed under CT at both levels of residue retention at 0–0.15 m soil depth. The N accumulation rate under HR was 24.5 kg N ha −1 higher than LR. The N balance calculation over 2.5 years indicated an estimated soil N gain (8–11%) in SPHR and SPLR but a loss in CT. In CDS, neither treatments accumulated soil N but N losses were greater in CT. The effect of crop establishment methods on soil NH₄-N and NO₃-N at the early growth stage of cool dry season cropping was small and inconsistent. However, SP with HR maintained higher overall crop and system N uptake compared to CT and LR. Thus, CA practices altered the N balance which slowed the decline in soil N-stocks in the cereal-dominated rotation while resulting in a positive N balance in the legume-dominated rotation.

The tillage method determines several soil physical parameters that affect the emergence of post-rice chickpea (Cicer arietinum L.) in the Indo-Gangetic Plain of South Asia. Mechanised row-sowing with minimum soil disturbance and crop residue retention in medium-to-heavy-textured soils will alter the seedbed when compared to that prepared after traditional full tillage and broadcast sowing. Whilst minimum soil disturbance and timely sowing may alleviate the soil water constraint to crop establishment, other soil physical properties such as soil strength, bulk density, and aggregate size may still inhibit seedling emergence and root elongation. This study’s objective was to determine the limitations to chickpea crop establishment with increasing bulk density and soil strength, and different aggregate sizes below and above the seed. In two growth cabinet studies, chickpea seed was sown in clay soil with (i) a bulk density range of 1.3–1.9 Mg m−3 (Experiment 1) and (ii) the combination of bulk densities (1.3 and 1.8 Mg m−3) and aggregate sizes (<2 mm and >4 mm) above and below the seed (Experiment 2). Root length was significantly reduced with increasing bulk density (>1.4 Mg m−3), and soil strength impeded early root growth at >1 MPa. Where main root growth was impeded due to high bulk density and soil strength, a greater proportion of total root growth was associated with the elongation of lateral roots. The present study suggests that the soil above the seed needs to be loosely compacted (<1.3 Mg m−3) for seedling emergence to occur. Further research is needed to determine the size of the soil aggregates, which optimise germination and emergence. We conclude that soil strength values typical of field conditions in the Indo-Gangetic Plain at sowing will impede the root growth of chickpea seedlings. This effect can be minimised by changing tillage operations to produce seedbed conditions that are within the limiting thresholds of bulk density and soil strength.

Land development is rapidly occurring on sand-dominant soils that cover substantial areas of the Lower Mekong Basin (LMB). Sands are at risk of degradation on sloping uplands where agriculture is expanding and on lowland landscapes where intensification of cropping is occurring. Sandstone and granitic geology explain the prevalence of sand-dominant textures of profiles in the LMB. However, the sand terrains in uplands of Cambodia and Southern Laos mostly have not been mapped in detail and the diversity of their edaphic properties is poorly understood. On high-permeability sands, lowland rainfed rice crops are drought-prone, while nutrient losses from leaching are also a risk. Furthermore, waterlogging, inundation and subsoil hardpans are significant hazards that influence the choice of crops and forages for lowland soils. Soil acidity, low nutrient status, hard-setting and shallow rooting depth are significant constraints for crops and forages on sands in the lowlands. Land use change in the lowlands to alternative field crops and forages on sands is contingent on their profitability relative to rice, the amounts and reliability of early wet season rainfall, and the amounts of stored water available after harvesting rice. Low soil fertility and soil acidity are limitations to the productivity of farming systems on the sand profiles in uplands, while erosion, low soil organic matter levels and water balance are concerns for their sustainable use. Site-/soil-specific fertilizer and lime management, land suitability assessment and the use of conservation agriculture principles (minimum tillage and crop residue retention) can overcome some of these constraints.

Physical subsoil constraints, such as high soil strength, low porosity or unfavourable pore characteristics, impair crop water use, either through effects on water availability or the ability of the crop to access the water. By reducing the capacity of the soil to store water or by impeding infiltration or drainage, physical subsoil constraints can alter the availability of water to the crop. By delaying root exploration, reducing ultimate rooting depth or reducing the efficiency with which water is extracted from a soil zone, they can reduce the crop’s ability to access water present. The resultant impact on crop water use is modulated by factors including the amount and distribution of rainfall, the soil’s water holding capacity and the depth and severity of the constraint. While the processes by which subsoil constraints influence crop water uptake are generally well-understood, important aspects still need clarification or quantification. There are still many questions regarding processes of water transfer from the bulk soil to the roots’ vascular elements. New knowledge will need to be effectively linked with our understanding of water uptake at the scale of the crop or soil profile. There is also a need to improve knowledge of the influence of agronomic management on pore size distribution, continuity and stability in terms of their influence on root system development. Finally, simulation studies that evaluate the interaction of access to water with differing soil types and climatic zones will provide important extrapolation to allow the agronomic importance of subsoil constraints to be quantified in the context of inter-annual variation in rainfall distribution.

Aluminum (Al) toxicity poses a significant challenge for the yield improvement of chickpea, which is an economically important legume crop with high nutritional value in human diets. The genetic basis of Al-tolerance in chickpea remains unclear. Here, we assessed the Al-tolerance of 8 wild Cicer and one cultivated chickpea (PBA Pistol) accessions by measuring the root elongation in solution culture under control (0 μM Al3+) and Al treatments (15, 30 μM Al3+). Compared to PBA Pistol, the wild Cicer accessions displayed both tolerant and sensitive phenotypes, supporting wild Cicer as a potential genetic pool for Al-tolerance improvement. To identify potential genes related to Al-tolerance in chickpea, genome-wide screening of multidrug and toxic compound extrusion (MATE) encoding genes was performed. Fifty-six MATE genes were identified in total, which can be divided into 4 major phylogenetic groups. Four chickpea MATE genes (CaMATE1-4) were clustered with the previously characterized citrate transporters MtMATE66 and MtMATE69 in Medicago truncatula. Transcriptome data showed that CaMATE1-4 have diverse expression profiles, with CaMATE2 being root-specific. qRT-PCR analyses confirmed that CaMATE2 and CaMATE4 were highly expressed in root tips and were up-regulated upon Al treatment in all chickpea lines. Further measurement of carboxylic acids showed that malonic acid, instead of malate or citrate, is the major extruded acid by Cicer spp. root. Protein structural modeling analyses revealed that CaMATE2 has a divergent substrate-binding cavity from Arabidopsis AtFRD3, which may explain the different acid-secretion profile for chickpea. Pangenome survey showed that CaMATE1-4 have much higher genetic diversity in wild Cicer than that in cultivated chickpea. This first identification of CaMATE2 and CaMATE4 responsive to Al3+ treatment in Cicer paves the way for future functional characterization of MATE genes in Cicer spp., and to facilitate future design of gene-specific markers for Al-tolerant line selection in chickpea breeding programs.

Sustaining productivity of the rice-based cropping systems in the Eastern Indo-Gangetic Plain (EIGP) requires practices to reverse declining soil fertility resulting from excessive tillage and crop residue removal, while decreasing production costs and increasing farm profits. We hypothesize that the adoption of conservation agriculture (CA), involving minimum tillage, crop residue retention and crop rotation, can address most of these challenges. Therefore, the effects of crop establishment methods – strip planting (SP), bed planting (BP) and conventional tillage (CT); and levels of crop residue retention – high residue (HR) and low residue (LR) on individual crop yield, system yield and profitability were evaluated in a split-plot design over three cropping seasons in two field experiments (Alipur and Digram sites) with contrasting crops and soil types in the EIGP. The SP and BP of non-rice crops were rotated with non-puddled rice establishment; CT of non-rice crops was rotated with puddled transplanted rice. In the legume-dominated system (rice-lentil-mung bean), lentil yields were similar in SP and CT, while lower in BP in crop season 1. A positive effect of high residue over low residue was apparent by crop season 2 and persisted in crop season 3. In crop season 3, the lentil yield increased by 18–23% in SP and BP compared to CT. In the cereal-dominated system (rice-wheat-mung bean), significant yield increases of wheat in SP and BP (7–10%) over CT, and of HR (1–3%) over LR, were detected by crop season 3 but not before. Rice yields under CA practices (non-puddled and HR) were comparable with CT (puddled and LR) in both systems. Improved yield of lentil and wheat with CA was correlated with higher soil water content. The net income of SP increased by 25–28% for dry season crops as compared to CT and was equal with CT for rice cropping systems. Conservation agriculture practices provide opportunities for enhancing crop yield and profitability in intensive rice-based systems of the EIGP of Bangladesh.

Studies of rice-based systems in the Indo-Gangetic Plain (IGP) have demonstrated the beneficial effects of Conservation Agriculture on soil organic carbon (SOC) status, along with increased soil health and crop productivity. However, it remains unclear as to the time for such treatments to have a positive effect. In this study of lentil-mung bean-rice and wheat-mung-rice rotations in Bangladesh positive effects of strip planting or bed planting, along with residue return, on SOC pools were apparent after 1.5 years, compared with intensive conventional tillage and limited residue return. Conventional tillage resulted in higher CO2 emission compared with strip planting or bed planting as did high residue return. In the cereal-dominated rotation, the strip planting system sequestered carbon at a rate of 0.24–0.53 Mg C ha−1 year−1 (at 0–0.15 m depth) while conventional tillage was associated with a carbon loss of 0.52–0.82 Mg C ha−1 year−1. In the legume-dominated rotation, neither practice sequestered SOC. Under strip planting, a minimum annual crop residue input of 1.7 Mg C ha−1 for the cereal-dominated system and 5.2 Mg C ha−1 for the legume-dominated system was required to maintain SOC at equilibrium. We conclude that strip planting with high levels of crop residue return can be an effective and quick strategy in either slowing the loss of SOC or improving C sequestration in the intensive rice-based systems of the Eastern IGP.