Effects of Different Wheat Tissues on the Population Parameters of the Fall Armyworm (Spodoptera frugiperda)

The fall armyworm (FAW), Spodoptera frugiperda, is an invasive migratory pest that prefers to feed on crops of the Gramineae family such as maize and wheat. It has been recorded in different locations in China since its invasion in 2019. To assess its effect on different wheat tissues and to provide a risk evaluation for wheat fields, FAW larvae were reared on the wheat seedling (WS), spike (SPK), peduncle (PDC), flag leaf blade (F-b), and blade of the first leaf under flag (F-1b). The population parameters were recorded, and the data were analyzed using the age-stage, two-sex life table method. The results showed that the FAW achieved successful development on all the substrates, although those fed on F-1b grew the slowest, had the smallest pupal weight, and deposited the fewest eggs. The larval survival rates of those fed on WS, SPK, and PDC were more than 80%, while for F-b and F-1b they were 56.58% and 32.03%, respectively. Feeding on leaf blades also resulted in lower fertility, reproductive capacity, life expectancy, net reproductive rate, intrinsic rate of increase, and finite rate of increase. These results indicated that feeding on WS, SPK, and PDC were more beneficial for development compared to F-b and F-1b alone. However, leaf blades alone can still support the full FAW lifecycle and thus could play an important role in nutrition, especially when quantities of the preferred host tissues are not sufficient. These results provide guidance for assessing the FAW risk in China.

Pathotype Identification and Virulence Variation in Cochliobolus sativus in China

Spot blotch caused by Cochliobolus sativus has become an important disease in the wheat-growing regions in China due to changes of regional climate, agricultural cultivation pattern and widely growing susceptible wheat varieties. Little information is available about virulence variability and pathogenic specialization of the C. sativus isolates from major wheat-growing regions in China. Here, 12 representative wheat varieties and foundation breeding stocks were selected to characterize the pathotypes of C. sativus isolates from infected wheat plants. Based on the infection phenotypes in the 12 differential genotypes at the seedling stage, 70 Chinese pathotypes were identified from 110 isolates and clustered into three virulence groups. The high virulence isolates were collected from wheat leaves, crowns, and roots, with most (10 of 14) from the Henan province in the Huang-Huai plain. No relationship was evident between virulence variability of C. sativus isolates and their geographic origins or types of diseased wheat tissues. Cochliobolus sativus showed a significant pathogenic specialization in hosts of wheat and barley. Most of the wheat isolates (50 of 65) were avirulent to all the differential barley genotypes, and a few were virulent only to highly susceptible barley genotypes. These results indicated that C. sativus isolates from the wheat-growing regions in China varied considerably for their virulence in wheat varieties, and showed significant pathogenic specialization to the wheat and barley hosts.

Characterization of the microbial communities in wheat tissues and rhizosphere soil caused by dwarf bunt of wheat

Dwarf bunt of wheat, which is caused by Tilletia controversa J.G. Kühn, is a soil-borne disease which may lead up to an 80% loss of yield together with degradation of the quality of the wheat flour by production of a fishy smell. In this study, high-throughput sequencing technology was employed to characterize the microbial composition of wheat tissues (roots, spikes, first stem under the ear, and stem base) and rhizosphere soil of wheat varieties that are resistant and susceptible to T. controversa. We observed that the soil fungal community abundance and diversity were higher in resistant varieties than in susceptible varieties in both inoculated and uninoculated wheat, and the abundances of Sordariomycetes and Mortierellomycetes increased in the resistant varieties infected with T. controversa, while the abundances of Dothideomycetes and Bacteroidia increased in the susceptible varieties. Regarding the bacteria present in wheat tissues, the abundances of Chloroflexi, Bacteroidetes, Gemmatimonadetes, Verrucomicrobia and Acidobacteria in the ear and the first stem under the ear were higher than those in other tissues. Our results indicated that the abundances of Sordariomycetes, Mortierellomycetes, Leotiomycetes, Chryseobacterium and Massilia were higher in T. controversa-infected resistant varieties than in their controls, that Dothideomycetes, Bacteroidia, Nocardioides and Pseudomonas showed higher abundances in T. controversa-infected susceptible varieties, and that Curtobacterium, Exiguobacterium, Planococcus, and Pantoea may have higher abundances in both T. controversa-infected susceptible and resistant varieties than in their own controls.

Co-expression network analysis of the genes associated with pistillody-stamen development in wheat

Background: Crop male sterility has great values in both theoretical research and breeding application. Wheat pistillody-stamen is an important male sterility phenomenon, and HTS-1 is an important pistillody-stamen material. However the molecular mechanism of HTS-1 stamens transformed into pistils or pistil-like structures remains a mystery. Weighted gene co-expression network analysis (WGCNA) are widely used to explore hub genes and gene interaction networks from high throughput data in various plants. Results: In the present study, for exploring gene networks associated with wheat pistillody-stamen development, WGCNA was employed to analyze 11 RNA-sequencing (RNA-seq) data of wheat tissues, including stamens of CSTP, pistils and pistillody-stamen of HTS-1. 19 out of 25 merged modules were highly associated with specific wheat tissues, and the MEdarkseagreen1 module was highly related to wheat pistillody-stamen (correlation with weight r =0.7, correlation p-value p =0.02). Then 180 genes about wheat flower development were identified from the MEdarkseagreen1 module by GO term analysis. Among 180 genes, the hub gene number associated with anther, filament, style, and ovary development were 12, 3, 3, and 10, respectively. We compared the published pistillody related proteins with proteins of HTS-1 by BLAST. A total of 58 pistillody-stamen development associated proteins were validated by BLAST. MADS-box and YABBY transcription factor about pistillody-stamen development were also analyzed in wheat flower. There were 47 of MADS-box and 17 of YABBY transcription factors were identified. BLAST program was used to align the published pistillody associated MADS-box and YABBY transcription factors with transcription factors identified in wheat flower. Totally, 36 of 47 MADS-box and 14 of 17 YABBY transcription factors were considered to regulate the development of pistillody-stamen, which had never been reported yet. Conclusion: These results have systematically identified the key candidate genes about the development of HTS-1 substructures flower. The tissue-specific correlation network analyses provide important insights into the molecular interactions underlying psitillody-stamen development.

Bacillus velezensis CC09: A Potential ‘Vaccine’ for Controlling Wheat Diseases

Biocontrol bacteria that can act like a “vaccine”, stimulating plant resistance to pathogenic diseases, are still not fully elucidated. In this study, an endophytic bacterium, Bacillus velezensis CC09, labeled with green fluorescent protein, was tested for its colonization, migration, and expression of genes encoding iturin A synthetase within wheat tissues and organs as well as for protective effects against wheat take-all and spot blotch diseases. The results showed that strain CC09 not only formed biofilm on the root surface but was also widely distributed in almost every tissue, including the epidermis, cortex, and xylem vessels, and even migrated to stems and leaves, resulting in 66.67% disease-control efficacy (DCE) of take-all and 21.64% DCE of spot blotch. Moreover, the gene cluster encoding iturin A synthase under the control of the pitu promoter is expressed in B. velezensis CC09 in wheat tissues, which indicates that iturin A might contribute to the in-vivo antifungal activity and leads to the disease control. All these data suggested that strain CC09 can act like a ‘vaccine’ in the control of wheat diseases, with a single treatment inoculated on roots through multiple mechanisms.

Elevated ozone level affects micronutrients bioavailability in soil and their concentrations in wheat tissues

To investigate the bioavailability of essential micronutrients (Fe, Mn, Cu, Zn) in soil-plant system, sequential scheme of weak acid soluble (WAS), reducible (RED) and oxidizable (OXI) fractions was used to evaluate the bioavailability of micronutrients in different soil depths. The results revealed that at the tillering stage elevated O₃ concentration significantly increased WAS-Fe at 0–5 cm and 10–15 cm soils by 69.11% and 59.72%, respectively. At the ripening stage, both WAS-Cu and RED-Cu were significantly increased in elevated O₃ treatment compared to control, while WAS-Mn only showed significant in 0–5 cm soil. In bulk soil, WAS-Zn and RED-Zn concentrations were generally greater than those in control, which was more evident at 10–15 cm soil. Besides, O₃ decreased the whole plant biomass by 14.63% and increased the root to shoot ratio. Elevated O₃ significantly increased grain Fe, Mn and Cu concentrations by 9.37, 36.68 and 48.18%, respectively, while it decreased Zn by 17.09%. It can be inferred that altered micronutrients bioavailability in soil and nutrients uptake in plants are likely associated with the changed soil chemical properties and plant physiology in response to the rising O₃ level.