Transcriptome Profiles of Sporisorium reilianum during the Early Infection of Resistant and Susceptible Maize Isogenic Lines

The biotrophic fungus Sporisorium reilianum causes destructive head smut disease in maize (Zea mays L.). To explore the pathogenicity arsenal of this fungus, we tracked its transcriptome changes during infection of the maize seedling mesocotyls of two near-isogenic lines, HZ4 and HZ4R, differing solely in the disease resistance gene ZmWAK. Parasitic growth of S. reilianum resulted in thousands of differentially expressed genes (DEGs) compared with growth in axenic culture. The protein synthesis and energy metabolism of S. reilianum were predominantly enriched with down-regulated DEGs, consistent with the arrested hyphal growth observed following colonization. Nutrition-related metabolic processes were enriched with both up- and down-regulated DEGs, which, together with activated transmembrane transport, reflected a potential transition in nutrition uptake of S. reilianum once it invaded maize. Notably, genes encoding secreted proteins of S. reilianum were mostly up-regulated during biotrophy. ZmWAK-mediated resistance to head smut disease reduced the number of DEGs of S. reilianum, particularly those related to the secretome. These observations deepen our understanding of the mechanisms underlying S. reilianum pathogenicity and ZmWAK-induced innate immunity.

Gains in recurrent selection cycles for grain yield and resistance to head smut in maize

El basidiomiceto <em>Sporisorium reilianum</em> f. sp. <em>zeae</em> infecta al cultivo de maíz y causa importantes pérdidas en regiones donde existen condiciones propicias para el desarrollo de la enfermedad. En este trabajo se evaluó la respuesta a la selección de seis ciclos de selección recurrente de maíces de endospermo blanco y cinco ciclos de maíces de endospermo amarillo para caracteres agronómicos deseables, rendimiento de grano y resistencia al carbón de la espiga. Los diferentes ciclos en las dos poblaciones se obtuvieron siguiendo el método de selección recurrente de familias S1, los cuales fueron evaluados para determinar el avance genético. En un ensayo anexo, las poblaciones fueron inoculadas artificialmente para medir el progreso de la resistencia a la enfermedad y evaluar un nuevo método de inoculación. Se utilizó un diseño experimental de bloques completos al azar con tres repeticiones para el ensayo de rendimiento y dos repeticiones para el ensayo inoculado. Los ciclos evaluados en las dos poblaciones mostraron un incremento en la resistencia de 0.94 y 1.2% ciclo-1, una ganancia genética para rendimiento de grano de 272.9 y 620 kg ha-1 ciclo-1 para la población blanca y amarilla, respectivamente. Los resultados mostraron que la selección recurrente de familias S1 fue eficiente para mejorar el rendimiento de grano y resistencia al carbón de la espiga en ambas poblaciones.

Maize Head Smut: Pathogenesis, Epidemiology, and Management Options

Maize (Zea mays) head smut caused by Sphacelotheca reiliana, a basidiomycete with worldwide distribution, can cause devastating crop losses that pose a food security threat. While Kenya has experienced high incidences of the disease in the recent years, the seed certification regulation has a zero tolerance on S. reiliana. The spores of S. reiliana remain viable in soil for many years and serve as the main inoculum source as they germinate when the conditions are favourable and infect the host in the early stages of growth after germination. After penetration, the fungus grows systemically as the plant matures eventually transforming part or all of the inflorescence (ears and tassels) tissues into smut galls. The symptoms develop because the inflorescences have increased levels of reactive oxygen species, auxin, and misregulation of floral regulatory transcription factors. The most practical control strategy for maize head smut encompasses the use of resistant/tolerant cultivars, fungicide treatment (of seed or drenching of rows immediately after seeding), and field hygiene/ sanitation. Crop rotation may help when host crops are not planted for between 2-3 years or even more. Resistance genes, including ZmWAK, found in the major quantitative trait locus qHSR1/qHS2.09 regulate resistance of maize to head smut. The objective of this review paper is to provide an understanding of the head smut disease pathogenesis, epidemiology, and effective management options. Key words: Sphacelotheca reiliana, basidiomycete, seed certification, smut galls, resistance gene

The effectiveness of fungicides against blister smut and fusarium on the cobs in growing self-pollinated corn lines

In the Stavropol Territory and in the Kabardino-Balkarian Republic of late, the most harmful and dominant diseases of corn are blister smut and fusarium on the cob. It has been established that the most harmful damage to the ears, in which the productivity of plants decreases by 30-50%. Studies carried out in 2018-2019 showed that seed infections are due to a high (54-66%) prevalence of diseases of the ears, such as fusarium, blister and head smut. The severity of the blister smut depends on the stability of the hybrid, the timing of infection, which organ is affected and weather conditions.

Quantitative determination of trypsin inhibitor as a breeding marker in maize varieties with different resistance to fungal diseases

Determination of plant resistance to fungal pathogens is an important breeding component. Thus, the study of protein profiles from corn kernels (13 genotypes) revealed a constitutively pronounced 14 kDa protein, trypsin inhibitor (TI), which is present at a relatively high level of concentration in seven Aspergíllus flavus - resistant maize lines, but at low concentrations or is absent in six sensitive lines. The 14 kDa trypsin inhibitor (TI) also showed antifungal activity against other mycotoxicogenic species. In this regard, the task was to determine the content of TI in varieties of maize with known properties, resistance, or sensitivity to such fungal pathogens of maize as head smut, common smut, and Fusarium stalk rot. According to the data obtained, the content of TI varies in different varieties and can vary by 4 times. However, in disease-resistant varieties its content is increased, which may be the primary marker of resistance of the variety to fungal pathogens.