Context. Salt stress harms plant growth and limits crop productivity. Autophagy is a material decomposition and metabolism pathway that is central to regulating plant responses to environmental stimuli and may be employed in plant breeding for stress tolerance. The autophagy-related gene ATG8 has become an essential tool for monitoring autophagic activity.

Aims. We aimed to determine the effects of increased autophagic activity via overexpression of ATG8 on tolerance of wheat (Triticum aestivum L.) seedlings to NaCl stress.

Methods. Salt-tolerant wheat cv. Jimai22 was used to produce TaATG8a-overexpressing wheat seedlings using Foxtail mosaic virus based virus-mediated overexpression technology. TaATG8a-overexpressing seedlings were exposed to NaCl stress for 6 days.

Key results. Overexpression of TaATG8a enhanced autophagic activity and improved salt stress tolerance of wheat seedlings. Overexpression of TaATG8a also reduced damage to photosystem II, reduced excess accumulation of reactive oxygen species, increased the activities of superoxide dismutase, peroxidase and catalase, and suppressed programmed cell death in wheat seedling leaves during NaCl treatment.

Conclusions. Overexpression of TaATG8a conferred higher tolerance of wheat seedlings to NaCl stress and suppressed salt-induced programmed cell death, accompanied by increased autophagic activity.

Implications. This study provides genetic resources and a theoretical basis for stress tolerance breeding in wheat.

Contexts. Increasing the availability of phosphorus fertiliser is needed for better crop production in acidic soils.

Aims. To observe how rice straw and its biochar affect phosphorus fertiliser recovery in an Ultisol and an Oxisol as a measure for the availability of phosphorus in acidic soils.

Methods. A 60-day incubation study was conducted using treatments comprising of straw (1.5%, w/w) and biochar produced at 400°C (1.5%, w/w), a mixture of each at the same rate, and a control with two phosphorus rates of 0 and 100 mg kg⁻¹.

Key results. The application of both the straw and the biochar alone and in combination raised the soil pH by 0.12, 0.20, 0.32, 0.17, 0.31 and 0.38 units, and cation exchange capacity by 2.06, 3.02, 2.72, 2.56, 6.28, and 8.40% compared to control for both the Ultisol and the Oxisol, respectively. Similarly, dissolved organic matter also increased by 74.19, 55.28, 84.63, 24.39 and 136.44%, respectively compared to control for the corresponding treatments and soils except the straw amended Ultisol. With an increase in the soil pH, the rate of phosphorus recovery increased by 11.73, 12.99, 23.89, 2.72, 5.23 and 6.28% compared to control for the corresponding treatments and soils, respectively. Phosphate adsorption by the soils became hindered by increased cation exchange capacity and dissolved organic matter but decreased exchangeable trivalent aluminium cations, which led to a greater phosphorus recovery in both the amended soils.

Conclusions. The combined application of rice straw and biochar would be the appropriate choice for increasing the applied phosphorus fertiliser availability in acid soils.

Context. Establishment of true heterotic pattern in maize germplasm can increase the efficiency of hybrid breeding. Heterosis is dependent on the genetic diversity of parents and the extent of dominance at different loci. Estimation of genetic diversity through use of molecular markers is routine practice in maize breeding.

Aims. The present study was designed to test whether simple sequence repeat (SSR) markers linked to yield-contributing traits are more reliable for heterotic grouping than random SSRs.

Methods. Diallel crosses developed among 19 inbred lines were evaluated at multi-locations. The genotypes were also grouped using polymorphic random (50) and linked (47) SSRs.

Key results. The crosses generated with lines belonging to different heterotic groups of linked SSR markers did not reveal any superiority over the crosses of the diallel set. By contrast, mean performance of inter-heterotic group crosses generated on the basis of random markers was superior to that of intra-heterotic crosses. Specific combining ability effects did not reveal any significant association with genetic distance of random or linked markers.

Conclusions. The lack of improved efficiency of linked markers over random markers can be attributed to factors including the quantitative nature of the trait, genotype × environment interactions, genetic background of germplasm in which the markers are expressed, and multiple alleles.

Implications. Markers linked to yield-contributing traits are no more reliable for heterotic grouping than random markers.

Context. Vicia sativa subsp. macrocarpa (V. macrocarpa), a large-seeded vetch, is underutilised and has been proposed as a putative source of seed feed along with V. sativa subsp. sativa (V. sativa, common vetch).

Aims. The study aimed to compare the two subspecies for a range of seed yield and quality traits.

Methods. Three accessions of each subspecies were grown under field conditions during two growing seasons. Measurements included pod and seed morphology, seed yield per plant, pod shattering and seed toughness, seed nutritional traits, and insect damage.

Key results. No significant differences were found for seed weight per plant (9.95–14.75 g); however, V. macrocarpa accessions showed lower emergence percentages (7–18%) and higher pod shattering (4.01% vs 0.17%) than V. sativa. The higher number of seeds per pod (8.50 vs 7.49) and larger seeds (70.63 vs 59.67 g) significantly contributed to yield of V. macrocarpa. Over the six accessions, seed weight per plant was significantly correlated with harvest index. The darker seeds of V. macrocarpa had lower seed protein concentration (25.96% vs 27.89%) and higher concentrations of antinutritional phenolic compounds (total phenols, total tannins, condensed tannins, flavonoids). Seeds of V. macrocarpa were enriched in manganese (17.72 vs 12.65 mg/kg) compared with V. sativa, but poorer in potassium (8.44 vs 10.50 g/kg). The high manganese and phenolics concentrations in seeds of V. macrocarpa were associated with lower percentages of bruchid-infected seeds and endoparasitoid (Triaspis thoracicus) damaged seeds, possibly due to toxic effects.

Conclusions. The two subspecies varied significantly in seed quality traits, but not yield.

Implications. More extensive comparisons between the two subspecies, with larger numbers of accessions, are needed in order to determine the potential of V. macrocarpa as a source of seed feed.

Context. Studies of Phoma black stem and leaf spot disease (caused by Phoma medicaginis) in annual medics (Medicago spp.) normally involve a ‘once-only’ inoculation not reflecting multiple pathogen infection and phytoestrogen production cycles in the field. Phytoestrogen production by plants can result in lower ovulation rates in grazing animals.

Aims. We aimed to determine whether sequential infections by P. medicaginis increase production of phytoestrogens in annual medics, and to measure the genetic diversity of isolates.

Methods. In a greenhouse experiment, pathogenicity and virulence were investigated across 32 isolates of P. medicaginis following one, two or three rounds of inoculation of M. polymorpha var. brevispina. Production of the phytoestrogens coumestrol and 4′-O-methyl coumestrol was measured, and correlation with disease parameters assessed. DNA sequencing using ITS, β-tubulin, calmodulin and P. medicaginis-specific EFNI-1α was applied for phylogenetic analysis of isolates from Western Australia and elsewhere.

Key results. Across isolates, highest leaf disease incidence was 76%, petiole disease incidence 61%, leaf disease severity 52% and petiole disease severity 53%. Stem coumestrol content range was 45–1247 mg kg⁻¹, and 4′-O-methyl coumestrol 0–344 mg kg⁻¹. All measures were highest after three rounds of inoculation. Overall, there was a positive correlation of leaf disease incidence with coumestrol content (P < 0.05) and of both leaf and petiole disease incidence with 4′-O-methylcoumestrol content (P < 0.01, P < 0.05, respectively). Phylogenetic analysis revealed a high degree of genetic similarity among Western Australian isolates, generally grouping into a single separate cluster across the four markers, and genetically distinct from isolates sourced outside Australia.

Conclusions. Leaf disease incidence was the best discriminating disease parameter for coumestrol and 4′-O-methylcoumestrol content. Western Australian isolates of P. medicaginis were genetically similar and unique, possibly due to geographic separation.

Implications. The study emphasised the importance of sequential inoculations when screening annual Medicago genotypes towards developing cultivars with superior disease resistance and enhanced animal reproductive outcomes.

Context. In the breeding of oilseed Brassica crops for human consumption and animal feed, the main objective is the expansion of commercial varieties with low erucic acid, low glucosinolates, and high oleic acid content. Indian cultivars are high in erucic acid and glucosinolates.

Aims. This study examined variation among species and genotypes of Brassica for early screening potential in breeding programs for enhanced oil quality of rapeseed mustard.

Methods. Seeds of 165 Brassica genotypes including exotic and indigenous collections from India were analysed for oil content, fatty acid composition of seed oil, and glucosinolate content in seed meal. Species represented were B. juncea (159 genotypes), B. rapa (2), B. napus (2), B. carinata (1) and Eruca sativa (1). Correlation, principal component and cluster analyses were performed.

Key results. Substantial genetic variability was detected among genotypes for all studied traits. Oil content ranged from 32% to 45%. Oleic (11.93–54.13%), linoleic (13.33–35.85%), linolenic (3.42–20.77%) and erucic (0–50.70%) acids were the dominant fatty acids. Erucic acid had a significant and negative association with oleic, linoleic, linolenic and eicosenoic acids. Glucosinolate content varied from 7.32 to 282.17 μmol/g in the defatted meal. The first two principal components accounted for 48.10% of cumulative variation. Genotypes were grouped into five major clusters. Genotypes of one cluster had high oleic acid (46.73%) and low erucic acid (1.72%).

Conclusions. Five promising genotypes were found with low glucosinolate (<30 μmol/g defatted meal) and low erucic acid (<2%) content (i.e. ‘00’ characteristics).

Implications. The inherent variation for seed oil quality traits across assessed Brassica genotypes suggests their potential for application in future breeding operations.

Context. Avena sterilis subsp. ludoviciana (wild oats) is one of the major winter weeds of the Northern Grains Region of Australia. The abundance of this weed increased dramatically after the adoption of no-tillage conservation agriculture (NTCA). However, information is lacking on the germination characteristics of the two types of seed (i.e. primary and secondary) that it produces.

Aims. We aimed to determine the light and temperature requirements for germination and the time to germination of primary and secondary seeds of A. ludoviciana, in order to find ways to manage this weed effectively under NTCA systems.

Methods. Primary and secondary seeds and caryopses from two southern and two northern biotypes were exposed to a range of temperature and light regimes in the glasshouse, and germination was assessed.

Key results. All biotypes had ∼25% higher germination from primary than secondary seeds. Removing the hull increased caryopsis germination by ∼70%. The use of a light/dark photoperiod stimulated germination of both types of seed and caryopses compared with continuous darkness. Based on data for caryopses, 7°C and 9°C were found to be optimal germination temperatures for southern and northern biotypes, respectively. At optimum germination temperature, primary caryopses germinated 7–20 days earlier than secondary caryopses. In addition, a light/dark environment resulted in germination 2–6 days earlier than continuous darkness.

Conclusions. In the Northern Grains Region, seeds retained on or close to the soil surface (i.e. in NTCA systems) can undergo maximum germination during May–June (late autumn–winter), when long-term average temperatures match optimum germination temperatures. This coincides with winter crop plantings.

Implications. The seasonal timing of germination and the difference in germination timing between primary and secondary seeds, which help to stagger emergence of this weed, are major issues that need to be addressed in NTCA systems.

Context. Lolium rigidum Gaudin (annual ryegrass) has remained the most problematic weed of crop production in Australia for more than 20 years. There is some evidence that this weed species can rapidly adapt to management practices including delayed crop sowing.

Aims. Studies were undertaken to determine genetic variation for seed dormancy within L. rigidum populations and its association with genes involved with gibberellic acid and abscisic acid synthesis.

Methodology. Populations of L. rigidum were grown in pots to select low and high dormancy cohorts. Seeds produced by these cohorts from each population were assessed for variation in seed dormancy. Seeds of high and low dormancy cohorts were concurrently assessed for seed dormancy and expression of LrABA1 and LrGA20ox genes, using quantitative real-time PCR.

Results. Presence of differences greater than two-fold in seed dormancy between populations from the same farm indicated in situ selection for seed dormancy, most likely in response to management. Low and high dormancy cohorts of all populations maintained clear differences in seed dormancy in both years of assessment. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with LrABA1 and LrGA20ox gene expression.

Conclusions. This investigation has provided clear evidence of the presence of genetic variation for seed dormancy within L. rigidum populations.

Implications. The presence of genetic variation for seed dormancy in L. rigidum populations will allow this weed to adapt rapidly to changes in weed management practices such as delayed sowing of crops.

Context. Bromus diandrus Roth is a serious weed of cereal-based cropping systems in South Australia. Its adaptation to local climate and production systems, prolific seed production and evolution of herbicide resistance have made this weed difficult to manage.

Aims. Studies were undertaken to determine genetic variation in seed dormancy within B. diandrus populations and its association with genes involved with gibberellic acid and abscisic acid synthesis.

Methodology. Seeds from five B. diandrus populations were sampled during 2017 from commercial fields and planted during 2018 in pots. Protracted seedling emergence in these populations allowed selection of low and high dormancy cohorts. Seeds produced by these cohorts from each population were evaluated for variation in seed dormancy in the following year. The process of cohort selection and seed dormancy evaluation was repeated. The mechanism regulating seed dormancy was investigated in 2020 by assessing seeds of low and high dormancy cohorts concurrently for dormancy and for expression of ABA1 and GA20ox genes, using quantitative real-time PCR.

Results. There was at least a two-fold difference in seed dormancy among populations collected from different farms. Low and high dormancy cohorts within each population maintained consistent differences in seed dormancy in both years of assessment, suggesting genetic control over this trait. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with ABA1 and GA20ox gene expression.

Conclusions. Large differences in seed dormancy exist between individuals in B. diandrus populations. The study has provided evidence of genetic variation for seed dormancy within B. diandrus populations, which was associated with ABA1 and GA20ox gene expression.

Implications. Presence of genetic variation for seed dormancy could play an important role in adaptation to escape pre-sowing weed-control tactics, meaning that B. diandrus could become an even greater problem in field crops grown in this region.

Context. Tropical pasture have been little explored for haymaking, due to lack of information regarding loss of nutrients and of forage dehydration.

Aims. This study aimed to evaluate the production aspects of tropical pasture hays.

Methods. To characterise forage dry mass yield and dehydration rate, we studied the grasses Marandú, Xaraés, Massai, Paredão, Planaltina and Tupã. The water soluble carbohydrates concentration curve, chemical composition and in situ rumen degradability of dry mass, crude protein and neutral detergent fibre were also determined.

Key results. The highest forage dry mass yield was observed in 2018, when Planaltina and Paredão performed best (6.28 and 5.26 ± 0.41 t of dry matter ha⁻¹, respectively). There was no genotype × dehydration time interaction (P = 0.81) on water soluble carbohydrates. Exposure to sun resulted in a linear decreasing effect (P < 0.01) on water soluble carbohydrates content, with loss of 5.03 g kg⁻¹ for each hour of exposure to the sun during the haymaking process. There was an interaction effect (P < 0.01) between type of material and genotype on the content of dry matter, mineral matter, crude protein and neutral detergent fibre (P < 0.01). In situ degradability of Massai grass dry mass was higher for the hay (758.0 and 253.8 ± 7.9 g kg⁻¹ for hay and in natura material, respectively).

Conclusions and implications. The greater amount of leaves in relation to stem indicates that Massai grass is more efficient in dehydration during the first hours of exposure to the sun, as well as sustaining lower losses.