Context. Regular genetic monitoring of rice diversity provides informed direction for plant breeders when selecting parents in breeding programs.

Aims. The investigation was conducted to assess the trends of decade-wise genetic diversity in popular Indian rice (Oryza sativa L.) genotypes.

Methods. We screened 62 genotypes including popular rice varieties released from the 1970s to 2010s in India along with landraces, using gene-specific markers and some of the key yield and yield-contributing traits.

Key results. Using gene-specific markers, genetic diversity has shown a downward trend from landraces to the 2010s. Qualitative analysis revealed that more alleles were present in landraces than released varieties. The disappearance of alleles was prominently observed in varieties released in the 1970s and even more so in the 2010s, which suggests that present-day cultivars are losing several valuable alleles of the key yield genes. Genetic diversity assessed using phenotypic data also exhibited a downward trend towards the 2010s. Molecular and phenotypic data on genetic diversity were used to group the rice genotypes, revealing that genotypes with common parents grouped together.

Conclusions. Genetic diversity has shown a downward trend from landraces to the 2010s, as assessed using both gene-specific markers and phenotypic data, although with slight deviations among various decades.

Implications. This study reinforces the fact that assessment of temporal trends in genetic diversity at regular intervals is warranted to meet future food demands while conserving on-farm crop diversity.

Context. Wheat (Triticum aestivum L.) adaptation is highly dependent on crop lifecycle duration, particularly the time at which flowering occurs in a specific environment. Frost, low solar radiation, heat and drought can significantly reduce yield if a crop flowers too early or late. Wheat genotypes have different lifecycle durations determined by plant responses to temperature (thermal time accumulation and vernalisation) and photoperiod. These responses are largely controlled by five phenology genes (two PPD1 and three VRN1 genes). Advances in crop phenology modelling suggest that flowering time under field conditions could be accurately predicted with parameters derived from photoperiod and vernalisation responses obtained in controlled environments.

Aims. This study quantified photoperiod and vernalisation responses of 69 Australian wheat genotypes selected for diversity at the PPD1 and VRN1 loci.

Methods. Spring and winter genotypes were grown in four controlled environments at a constant temperature of 22°C with photoperiod (17 or 8 h) and vernalisation (0 or 8 weeks) treatments as factors.

Key results. Thermal time from coleoptile emergence to flowering in spring genotypes was typically decreased more by long photoperiod than by vernalisation; the opposite was true for winter genotypes. Spring genotypes that were sensitive to vernalisation contained a sensitive allele at the Vrn-A1 locus.

Conclusions. There is large diversity in phenological responses of wheat genotypes to photoperiod and vernalisation, including among those with matching multi-locus genotype.

Implications. Data from this study will be used to parameterise and test a wheat phenology model in a future study.

Context. Allelopathy is recognised as a potential technology to control weeds, and could also be a suitable approach for enhancement of crop yield.

Aims. The study was conducted to investigate the allelopathic role of Averrhoa carambola leaf extract on growth, anatomical and physiological features of three wheat lines, namely 3094, 7076 and A2011.

Methods. Three dilutions i.e. 0% (control), 15% and 30% of the leaf aqueous extract were applied at 15 day intervals (total five applications) on wheat lines until maturity.

Key results. All wheat lines showed differential behaviour to allelochemicals of A. carambola leaf extract. Increased root area was accompanied by a high proportion of storage parenchyma tissues and enlarged vascular bundles in line 3094. Disintegration of root cortical parenchyma and complete transformation of chlorenchyma into sclerenchyma in stem was recorded in all wheat lines, particularly at the highest concentration of leaf extract. Line 7076 showed very different behaviour, as it possessed a proportionally enlarged root cortex, enlarged stem vascular bundles and increased leaf thickness, primarily at the highest concentration of leaf extract. Line A2011 was relatively more sensitive, indicating a significant reduction (P < 0.05) in root and stem area and deformed leaves.

Conclusions. A low concentration (15%) of leaf extract promoted growth and development, whereas a higher concentration caused significant reduction in growth and anatomical attributes.

Implications. A lower dose of Averrhoa leaf extract promoted growth and development in all wheat lines, and hence can be used as a growth promoter. A higher concentration is important for eradicating unwanted plants.

Context. Intercropping maize with tropical forages is known to provide multiple benefits for the agricultural sustainability in the Brazilian savanna. Despite that, more studies are needed to define strategies to improve soil quality and increase crop yield of subsequent crops.

Aims. This study aimed to evaluate the impacts of cultivating maize in monoculture or in double- and triple-intercropping with brachiaria and crotalaria on the chemical and microbiological attributes of soil, nutritional status of soybean, and the productivity of soybean and millet in succession in the cerrado of eastern Maranhão.

Methods. The intercropping systems implemented in 2017 were as follows: maize (Zea mays) + Urochloa ruzizienses (brachiaria); maize + Crotalaria juncea (crotalaria); maize + brachiaria + crotalaria; and monoculture maize as a control. In 2018 and 2019, soybean and millet were cultivated on the same plots.

Key results. The triple-intercropping promoted immediate improvement in the biological and chemical attributes of the soil, especially when compared with monoculture maize. Intercropping maize with brachiaria, with or without crotalaria, increased soybean productivity by 21% and millet by 44% in the subsequent year, compared with monoculture maize system. Intercropping maize with brachiaria, with or without crotalaria, increased the leaf concentrations of nitrogen, potassium, magnesium, and sulfur of the subsequent soybean crop, suggesting improved nutrient cycling with intercropped forages.

Conclusions. Intercropping maize + forage, especially brachiaria, can be recommended for crop rotation and succession systems in the Brazilian savanna.

Implications. These results quantified the benefits of crop rotation following intercropping with maize and forage, which can be an alternative for farmers in the Brazilian savanna.

Context. Seed weight is an important agronomic trait for determining yield and appearance quality of soybean (Glycine max (L.) Merr.). Understanding the genetic basis of seed weight might lead to improvement of these traits in soybean by optimising different genes or alleles controlling seed weight.

Aims. A major quantitative trait locus (QTL) for seed weight, qSW17.1, was identified previously. In this study, we used progenies of cultivated soybean and wild soybean (Glycine soja Sieb. and Zucc.) for further validation and characterisation of qSW17.1.

Methods. A BC₄F₂ population, a heterogeneous inbred family (HIF) population, and a pair of qSW17.1 near-isogenic lines (NILs) developed from progenies of a cross between cultivated soybean variety Jackson and wild soybean accession JWS156-1 were cultivated under field conditions. QTL analysis and candidate gene mining were conducted.

Key results. A QTL corresponding to qSW17.1, which explained 19.84% and 31.71% of the total phenotypic variance in BC₄F₂ and HIF populations, respectively, was detected. The NIL with the cultivated soybean allele showed higher shoot biomass than the NIL with the wild soybean allele under hydroponic growth conditions, suggesting that the large-seed-size allele of qSW17.1 might be beneficial in soybean seedling establishment. qSW17.1 was delimited to a physical interval of 2515 kb on chromosome 17. Glyma.17G108500 showed a large (~3.27-fold) difference in expression between the two NILs, and was considered a candidate gene underlying qSW17.1.

Implications. Our results provide valuable information regarding the genetic basis of seed weight control in soybean and its utilisation in soybean molecular breeding.

Context. Class III acyl-CoA-binding proteins such as those from dicots (Arabidopsis and grapevine) play a role in defence against biotrophic pathogens. The overexpression of the monocot Oryza sativa (rice) OsACBP5 in Arabidopsis and rice has been demonstrated to enhance broad-spectrum disease resistance against selected phytopathogens in OsACBP5-overexpressing (OsACBP5-OE) lines.

Aims. We aimed to develop transgenic rapid-cycling Brassica napus (B. napus-RC) and canola cv. Westar OsACBP5-OEs using tissue culture-based Agrobacterium-mediated transformation and to evaluate transgenic plants for resistance against Alternaria blight, blackleg and Sclerotinia rot diseases.

Methods. Transgenic B. napus-RC and cv. Westar OsACBP5-OEs were generated through Agrobacterium-mediated transformation using Agrobacterium strain LBA4404 harbouring a plasmid with the rice complementary DNA encoding OsACBP5 driven by the cauliflower mosaic virus 35S promoter. Alternaria blight and blackleg pathogen assays were based on infecting young cotyledons, while detached leaf assay was used to test the tolerance of B. napus plants toward Sclerotinia sclerotiorum.

Key results. Average transformation efficiencies of 24.2% and 29.1% were obtained for B. napus-RC and B. napus cv. Westar cotyledons respectively. OsACBP5-OE plants exhibited resistance 5 days after inoculation with Alternaria brassicae, 12 days after inoculation with Leptosphaeria maculans, and 24 h after inoculation with S. sclerotiorum.

Conclusions. Transformation of B. napus-RC was shown herein to be an effective trait testing platform for canola. This study also provides an insight into the usefulness of OsACBP5 in enhancing resistance to necrotrophic phytopathogens.

Implications. OsACBP5 can be overexpressed in other crops to generate pathogen-resistant varieties.

Context. In Serbia, common bean (Phaseolus vulgaris L.) production largely relies on improved commercial cultivars; however, many farmers still grow and maintain landraces. Productivity assessment of common bean landraces from Serbia may enrich knowledge of bean diversity from Western Balkans, Europe and worldwide.

Aims. The study aims were to describe the underlying structure of a selected set of landraces and commercial cultivars of common bean, identify relatedness of accessions, and determine breeding values.

Methods and key results. Overall productivity was assessed through main yield components during a 2-year field trial. Average seed yield per plant was 7.9 g, with 1000-seed weight 425 g, 7.4 pods per plant and 22.9 seeds per plant. Accessions were classified according to seed colour and shape, with the Albus group generally showing highest productivity traits. Phenotypic and genotypic variability of the selected set was previously determined. Principal component analysis was used to assess bean germplasm structure, revealing subdivisions partially according to gene pool (Mesoamerican or Andean), evident through the existence of one larger Andean group. Relatedness of genotypes was assessed by hierarchical cluster analysis. Additional variation concentrated within the Andean gene pool was detected. Positive correlations were observed among numbers of pods and seeds per plant, yield per plant and plant height. According to the Mantel test, positive associations were observed among productivity trait distance, genetic distance and descriptive trait distance.

Conclusions. Substantial variation in productivity was observed for bean landraces, with differences among gene pools and seed forms, revealing their agronomic value. Acknowledged structure of agronomic traits and recognised stratification will assist in multilevel organisation of common bean breeding programs.

Implications. Combined information on phenotypic, genotypic and productivity value should benefit selection of promising parental lines associating good agronomic performance with sufficient variability, according to consumer preferences.

Context. Banana production in Australia is in three primary sub-regions within tropical North Queensland and the industry faces a variety of challenges including costs of production, disease and pests, and environmental impacts. The range of soil characteristics and banana leaf nutrient status on banana farms has not previously been systematically described. This knowledge gap makes it difficult to adapt research, management recommendations, and regulations to the needs of the three primary growing sub-regions.

Aims. In this work, we aimed to identify key soil factors that differentiate growing sub-regions, and provide context for future research and industry regulation.

Methods. We characterised soil and banana leaf samples from 28 banana farms on soil types accounting for >85% of Australia’s banana production.

Key results. Variation in soil properties and leaf nutrient concentrations were driven largely by site- (principal component 1 in both cases) and management-related variables (principal component 2 in both cases). Management-related foliar nutrient concentrations did not differ between regions despite differences in the associated soil variables. The most important site characteristics appeared to be soil parent material and climate. The Mareeba sub-region has basaltic soils, low rainfall and temperature, whereas the other two sub-regions are hotter, wetter and have a variety of soil parent materials. Leaf nitrogen concentrations were mostly below the regulated limit for additional nitrogen fertiliser application.

Implications. Our findings can facilitate sub-region-specific site selection for research, extension, and monitoring and more targeted regulation of banana production- and environment-related issues.

Context. Plant secondary metabolites are of increasing interest for agriculture due to their diverse beneficial ecological functions. The forage crop white clover (Trifolim repens L.) has been intensively studied for its heritable polymorphism in the production of hydrogen cyanide (HCN), a toxic defense phytochemical. In fodder production, white clover accessions are selected for biomass production, whereby HCN production is an unwanted trait.

Aim. Although white clover is a legume crop species of global importance, little is known about the linkage between cyanogenesis and growth traits, in particular in combination with resistance-related phytochemicals, such as flavonoids. We aimed to identify differences in biomass production, estimated leaf flavonoid content, and trait correlations in cyanogenic (HCN-producing) and acyanogenic (not HCN-producing) individuals and accessions of white clover.

Methods. We analysed 51 white clover accessions from a German germplasm collection for variability in selected traits: cyanogenesis as equivalent electrode potential, estimated leaf flavonoid content, root and shoot production, leaf area, specific leaf area, and number of leaves produced.

Key results. Most accessions considered as cyanogenic were heterogeneous for HCN production. Chemical–morphological trait correlations differed between cyanogenic and acyanogenic plants. Acyanogenic individuals and accessions produced more and larger leaves compared to cyanogenic ones. Within cyanogenic accessions, the higher the HCN level of a plant, the fewer but larger leaves were produced.

Conclusions. Our results highlight the variation in HCN production within the selected accessions, which calls for a consistent approach for cyanogenesis-based categorisation.

Implication. This study demonstrates the potential of combining phytochemical traits with biomass production in white clover when selecting material in a breeding program.