A two-year experiment was carried out at Shenyang Agricultural University’s research field area in China to evaluate the impact of the combined application of straw mulch (0 and 8 t ha⁻¹) and biochar (0, 4, 12, and 36 t ha⁻¹) on the morphological traits and grain development of rainfed maize during 2018 and 2019. The results showed that straw mulch and different biochar application rates significantly impacted the maize growth index. Compared to non-biochar-treated soils, the introduction of straw mulch improved plant height, stem diameter, leaf area index (LAI), leaves, stem, root, and crop growth rate (CGR), and dry weight of rainfed maize crop. The highest plant height, stem diameter, LAI, leaves, stem, root growth rate, CGR, and dry weight of rainfed maize crop were reported when soil was treated with a higher rate of biochar (36 t ha⁻¹). Biochar increased grain filling rate while decreasing grain filling duration in rainfed maize crops. Our results indicate that straw mulch and biochar-based soil management strategies can improve the rainfed maize growth with the environmental benefits of global warming mitigation. However, due to the wide range of biochar properties, the interactions between straw mulch and biochar should be given special consideration in the maize cropping system.

Understanding the origins of variation in agricultural pathogens is of fundamental interest and practical importance, especially for diseases that threaten food security. Fusarium oxysporum is among the most important of soil-borne pathogens, with a global distribution and an extensive host range. The pathogen is considered to be asexual, with horizontal transfer of chromosomes providing an analog of assortment by meiotic recombination. Here, we challenge those assumptions based on the results of population genomic analyses, describing the pathogen’s diversity and inferring its origins and functional consequences in the context of a single, long-standing agricultural system. We identify simultaneously low nucleotide distance among strains, and unexpectedly high levels of genetic and genomic variability. We determine that these features arise from a combination of genome-scale recombination, best explained by widespread sexual reproduction, and presence–absence variation consistent with chromosomal rearrangement. Pangenome analyses document an accessory genome more than twice the size of the core genome, with contrasting evolutionary dynamics. The core genome is stable, with low diversity and high genetic differentiation across geographic space, while the accessory genome is paradoxically more diverse and unstable but with lower genetic differentiation and hallmarks of contemporary gene flow at local scales. We suggest a model in which episodic sexual reproduction generates haplotypes that are selected and then maintained through clone-like dynamics, followed by contemporary genomic rearrangements that reassort the accessory genome among sympatric strains. Taken together, these processes contribute unique genome content, including reassortment of virulence determinants that may explain observed variation in pathogenic potential.

Pakistan is among the top 15 citrus producing countries in the world, with an area of 199,000 ha and 19.7 MT annual citrus production. In 2014, a survey was conducted in three major citrus growing areas (Sargodha, Khushab and Bhalwal) of Punjab province, where 94% of Pakistan’s citrus production is concentrated (Tahir, 2014). Severe dieback was observed in orchards, resulting in 40% yield losses. Dead twigs of Citrus reticulata cv. Kinnow produced small black pustules. Other symptoms included leaf chlorosis that eventually affected the whole plant. Samples were collected from twigs of symptomatic plants with more than 40% canopy infection from different orchards. Short segments encompassing lesion margins were excised, surface-sterilized with 70% ethanol, placed on potato dextrose agar (PDA), and incubated at 30 ± 1°C for 3 days with 12 h alternate light and dark cycle. Two different fungal morphotypes were recovered in a 2:1 frequency ratio. To obtain pure cultures, hyphal tips were transferred onto fres...