Context. Mungbean (Vigna radiata (L.) Wilczek) is an important grain legume for food, feed, and green manure. Mungbean yield is highly variable due to fluctuating temperature and unpredictable rainfall.

Aims. To improve yield stability, it is critical to utilise a model that can simulate mungbean phenology, biomass, and yield accurately.

Methods. A thorough understanding of the physiological determinants of growth and yield is required to advance existing mungbean crop modelling capability. Currently, there is limited understanding of the physiological determinants of canopy and reproductive development and their variation in mungbean germplasm. Two experiments (controlled and field environments) were conducted at Gatton, Queensland, in 2018–19. Six Australian mungbean genotypes and one black gram (Vigna mungo L.) were grown under non-limiting conditions. Plant phenotypic traits (canopy development, time to first, 50% flowering, duration of flowering and podding, flower appearance, pod addition rates) were recorded.

Key results. Genotypes M10403 and Satin II had significantly higher leaf appearance rate (LAR). Genotypes with a greater LAR had higher number of leaves but lower individual leaf area. Genotypes varied significantly in time to first and 50% flowering, with Onyx-AU (black gram) and Celera II-AU flowering earliest. Flowering and podding rates, and duration of these phenological phases varied among genotypes. Total plant leaf area (TPLA) approached its maximum at mid-podding stage.

Implications. This study quantified the key phenotypic and physiological relationships associated with canopy and reproductive development, critical for the improvement of mungbean crop modelling required to accurately simulate growth and development and inform possible canopy constraints that are limiting mungbean productivity.

Aims and methods. An experiment was established in Australia in 2008 with 34 varieties of sugarcane, to determine disease development over the crop classes, and the relationship between resistance category and yield loss from sugarcane smut.

Key results. Yield loss was related to incidence and disease severity in different varieties. Susceptible varieties had > 40% smut infected plants in the plant crop whereas little smut infection was observed on intermediate and resistant varieties. Smut disease across all varieties increased from 5% incidence and 7% severity in the plant crop to 46% and 19% incidence and severity respectively in the first ratoon (first regrowth crop) and to 59% and 27% incidence and severity respectively in the second ratoon (second regrowth) crops. Strong negative correlations were observed for smut incidence (r = −0.57) and severity (r = −0.62) with cane yield in the second ratoon crop. For every percent of increase in smut incidence and severity, a loss of 574 kg and 756 kg of cane per hectare were estimated, respectively. Similarly, the losses of tonnes of sugar per hectare were estimated to 96 kg and 128 kg for each 1% increase in smut incidence and smut severity.

Conclusion. Regression analysis showed that yield loss can be reduced from > 40% for susceptible varieties to < 6% for resistant varieties.

Implications A relationship of different resistance categories and yield loss due to sugarcane smut has been established to develop a guide for growers in selecting appropriate varieties for a particular agroclimatic zone.

Megathyrsus maximus (Gatton panic) is a tropical grass highly valued both for its use as forage and for its biofuel potential. A major constraint in establishing pastures of this cultivar is the low viability and germination of seeds and the poor initial seedling establishment. We used non-thermal plasma (NTP, partially ionised gas) as a novel technology to treat seeds of this grass, aiming to improve their quality (i.e. germination traits). We also followed the performance of seedlings grown from NTP-treated seeds under field conditions by assessing seedling establishment, biomass production and forage quality during the first regrowth period, which is the critical period for pasture establishment. Two NTP treatments were performed through dielectric barrier discharges employing N₂ as carrier gas. Non-treated seeds served as the control. Results showed that the viability of NTP-treated seeds was, on average, 1.5-fold higher than the control, and that germination energy and germination percentage of treated seeds was superior to the control by 2.1-fold and 2.2-fold, respectively. A field experiment showed that seedling establishment parameters (dynamics of cumulative emergence, emergence coefficient, and weighted average emergence rate) and pasture early productivity (represented by shoot dry matter) were enhanced by NTP treatment (phenolic sheet–polyester film barrier and 3 min exposure), showing 1.4–2.6-fold higher values than the control, confirming the results of the laboratory assays. Although NTP markedly increased the shoot dry matter production of the pasture, which was related to higher tiller population density and greater tiller weight, it did not affect the forage quality of the plants grown in the field. We conclude that NTP technology is suitable to improve seed germination of Gatton panic, in turn leading to improvements in seedling establishment and biomass production under field conditions without compromising forage quality.

Context. Leaves at different heights in a canopy have differential roles on photosynthetic characteristics and yield but have not been compared systematically under plastic film mulching with drip irrigation.

Aims. To determine the temporal and spatial variation of morpho-physiological characteristics in relation to the benefit of mulched drip irrigation in spring maize growth.

Methods. Field experiments were conducted in northeastern China during 2017 and 2018 that included mulched drip irrigation (MD), non-mulched drip irrigation (ND), and traditional non-mulched rain-fed (CK) treatments.

Key results. MD significantly increased lower leaf area by 13.1–62.3%, upper leaf N content (N_mass) by 6.3–13.0%, and upper leaf photosynthetic capacity (A_max) and maximum carboxylation rate (V_cmax) by 13.4–42.3% and by 4.7–11.6%, respectively. There were close correlations between leaf physiological parameters (N_mass, carbon isotope discrimination (Δ), A_max, and V_cmax), and also between morphological parameters (leaf area (LA) with leaf mass per area (LMA), and LMA with leaf dry matter content (LDMC). As for time scale, leaf morphological parameters (LA, LMA, and LDMC) in the reproductive stage (R-stage) were higher than those in the vegetative stage (V-stage), while physiological parameters (N_mass, A_max, and V_cmax) were higher in the V-stage. This study indicated that MD treatment increased the photosynthetic area of lower leaves and the photosynthetic capacity of upper and middle leaves compared with non-mulched rainfed CK. In addition, an increase of net radiation absorbed by the canopy in MD was likely to correspond to a higher net photosynthetic rate, which was beneficial to yield accumulation in the treatment.

Conclusions. This study provided relevant information for the simulation of water and carbon flux under mulched drip irrigation.

ImplicationsThe research explained that the morpho-physiological characteristics of leaves at different canopy heights played different role on affecting maize yields under plastic film mulched drip irrigation.

Context. Salinity is a major cause of yield loss in wheat globally.

Aims and methods. To investigate the potential of silicon to minimise the effect of salinity in wheat, experiments were conducted using outdoor pots subjected to seven salinity treatments. Silicon (as potassium silicate K₂SiO₃) was applied as both a priming agent and foliar spray. Selected response functions were used to quantify wheat response to salinity as affected by silicon application.

Key results. Concentration of chlorophyll a, chlorophyll b and carotenoid decreased by 4.2, 3.6 and 1.4 mg/g FW respectively with increasing salinity up to an electrical conductivity of 14 dS/m. Increasing salinity levels increased maximum variable chlorophyll fluorescence yield in a dark-adapted state and decreased the photochemical quenching coefficient, the nonphotochemical quenching coefficient, non-photochemical quenching, actual quantum yield of PSII electron transport in the light-adapted state, and the apparent photosynthetic electron transport rate. The maximal efficiency of PSII photochemistry in the dark-adapted state was not significantly influenced by salinity. The response functions showed that the salinity threshold value and the salinity at which a given trait was reduced by 50% (EC₅₀) were 5.7 and 12.1 dS/m, respectively.

Conclusions. The combined treatment of silicon (priming × foliar spray) was found to be the most effective, increasing salinity threshold value and EC₅₀ by 32 and 2% respectively.

Implications. These findings give insight into the effects of salinity on wheat and demonstrate the potential of silicon applications to promote crop health in saline environments.

Context. Among biotic factors, bean anthracnose caused by Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara is one of the most destructive diseases of common bean (Phaseolus vulgaris L.). Resistance in common bean genotypes is controlled by anthracnose resistance loci (designated Co).

Aims. The objective of this study was to evaluate the presence of Co resistance genes in common bean genotypes from Turkey and to examine promising genotypes as candidates for parent plants in breeding studies.

Methods. The presence of Co resistance genes in 693 common bean genotypes from 35 provinces of Turkey was determined by 12 SCAR (sequence characterised amplified region), RAPD (random amplified polymorphic DNA), STS (sequence-tagged site) and CAPS (cleaved amplified polymorphic sequence) markers. The disease reaction of 40 agronomically promising genotypes to different pathogen isolates was evaluated in a pot study.

Key results. The results indicated the presence of Co-1, Co-1⁴, Co-1⁵, Co-2, Co-3³, Co-4, Co-4², Co-6, Co-10, Co-11 and Co-13 resistance genes, alone or in combination; Co-5 was not detected in any of the genotypes. Among the genotypes, Co-1⁵ was the most frequent resistance source, followed by Co-4, Co-6 and Co-11, respectively. Common bean genotypes carrying Co-1⁴, Co-2, Co-3³, Co-11 and Co-13 have been identified for the first time in Turkish germplasm. Five genotypes carrying the various combinations of Co-1, Co-1⁵, Co-4, Co-6, Co-10, Co-11 and Co-13 were resistant to all isolates in pathogenicity tests.

Conclusions. This study is the most comprehensive to date on Co genes linked to the resistance of common bean genotypes throughout Turkey and provides an important gene pool for breeding studies into bean anthracnose. Resistant genotypes identified will be useful as parent plants in resistance breeding studies.

Implications. Resistance genotypes carrying different Co genes to bean anthracnose will contribute significantly to the disease management strategy.

Waterlogging tolerance of eight C₄ and seven C₃ perennial forage grasses was reviewed. The median waterlogging duration was similar between species’ type, ranging between 18 and 21 days. Inter- and intra-species variability was found in shoot and root biomass in response to waterlogging. Urochloa brizantha (C₄), Brachiaria hybrid (C₄) and Dactylis glomerata (C₃) were the less tolerant species to waterlogging (shoot biomass median of 45%, 53% and 80% of controls), while U. humidicola (C₄), Paspalum dilatatum (C₄), Festuca arundinacea (C₃) and Lolium perenne (C₃) were the most tolerant (shoot biomass median of 97%, 101%, 87% and 94% of controls). A similar ranking of responses was found among species for root biomass. The formation of aerenchyma/root porosity (a key trait for waterlogging tolerance) was evaluated mainly in U. humidicola and P. dilatatum (C₄ waterlogging-tolerant species), which showed considerable constitutive porosity (13% and 32%) and final values of 30% and 41% under waterlogging. Net photosynthesis and stomatal conductance as typical leaf physiological responses matched species’ waterlogging tolerance, with the impact of hypoxia higher in C₃ than in C₄ species. Gaps in knowledge about waterlogging tolerance in forage grasses are: (i) additional studies on C₃ perennial grasses for temperate pasture areas prone to waterlogging, (ii) identification of traits and responses aiding plant recovery after waterlogging (and also during the stress), (iii) reassessment of waterlogging tolerance considering plant developmental stage (e.g. adult vs young plants), and (iv) evaluation of sequential (i.e. waterlogging − drought) and combined (i.e. waterlogging + salinity) stresses, which often co-occur in pasture lands.

Rotations and associated management practices in rainfed farming systems of southwest Australia have shifted towards intensified cropping. Survey data from 184 fields spanning 14 Mha of southwest Australia were used to document water use efficiency (WUE) and water-limited yield potential (WLYP) of commercial crops and crop sequences and identify biophysical variables influencing WUE. WUE achieved in commercial wheat crops was 10.7 kg grain/ha.mm. Using a boundary function Ywl = 25 × (WU − 45), farmers achieved 54% of WLYP. Climate variables affected WUE more than management and biotic variates, the highest latitude region having WUE of 9.0 kg grain/ha.mm, compared to 11.8 kg grain/ha.mm for regions further south. Increased soil nitrogen and nitrogen fertiliser increased WUE, as did sowing earlier; in keeping with farmers in southern Australia sowing crops earlier and trebling fertiliser nitrogen usage since 1990. Wheat yield and WUE increased a small amount after break crop or pasture (12.5 kg grain/ha.mm) compared to wheat grown after wheat (11.2 kg grain/ha.mm), due to good weed and root pathogen control, and high fertiliser nitrogen application. However, WUE of wheat declined to 8.4 kg grain/ha.mm when more than three wheat crops were grown in succession. Farmers continue to improve WUE with increased inputs and new technologies replacing some traditional functions of break crops and pasture. However, break crops and pastures are still required within the rotation to maintain WUE and break effects need to be measured over several years.

Context. A transgenic variety of soybean (Glycine max (L.) Merr.), H57, has been developed from wild-type variety Jack, with host-induced gene silencing of a chitin synthase gene (CHS) in soybean cyst nematode (SCN, Heterodera glycines Ichinohe), a devastating pathogen in soybean. H57 needs to be characterised for suitability to manage SCN, especially because rhizosphere microbial communities may be sensitive to genetically modified crops.

Aims. We aimed to evaluate the SCN resistance of H57 at the T₇ generation, and analyse the impact on the rhizosphere microbial community of planting H57 into SCN-infected soil.

Methods. Infection with SCN was assessed at 60 days after planting of H57 and Jack into SCN-infected soil by examining recovered cysts from rhizosphere soil and comparing with an infected bulk soil control. For analysis of rhizosphere microbial communities (bacterial and fungal), 16S and ITS amplicons were identified by high-throughput sequencing, and bioinformatic analysis was used to define operational taxonomic units. Alpha diversity, using five indexes, and relative abundance were determined.

Key results. Soybean H57 showed significantly enhanced and heritable resistance to SCN compared with Jack. The diversity and richness (abundance) of the bacterial community of H57 and Jack were significantly and similarly increased relative to the bulk soil. The fungal community of H57 had considerably lower abundance than both other treatments, and lower diversity than the bulk soil. The relative abundance of only two bacterial phyla (Acidobacteria and Actinobacteria) and one fungal phylum (Glomeromycota), and three bacterial genera (Candidatus_Solibacter, Candidatus_Udaeobacter and Bryobacter) and one fungal genus (Aspergillus), differed significantly between rhizosphere soils of H57 and Jack.

Conclusions. Host-induced gene silencing of SCN-CHS substantially and heritably enhanced SCN resistance in soybean, did not significantly alter the rhizosphere bacterial community, but greatly suppressed the abundance of the rhizosphere fungal community, which was likely associated with boosted SCN resistance.

Implications. This study established a basis for interaction research between soybean with SCN-CHS host-induced gene silencing and the rhizosphere microbial community, and for potentially planting soybean H57 to manage SCN.