Genome-wide Association Study of Kernel Black Point Resistance in Chinese Wheat Landraces

Black point (BP) disease of wheat has become a noticeable problem in China. The symptoms are brown to black in color around the wheat kernel embryo or in the endosperm, resulting in a significant reduction of wheat grain quality. Here, we evaluated 272 Chinese wheat landraces for BP reaction and performed a genome-wide association study (GWAS) to identify BP resistance quantitative trait loci (QTL) in five field environments without artificial inoculation. The BP incidence data showed continuous distributions and had low to moderate correlations between environments (r = 0.094 – 0.314). Among the 272 landraces, 11 had 0.1% to 4.9%, 144 had 5% to 14.9%, and 100 had 15% to 29.9%, and 17 had over 30% incidence. We found three resistant accessions: WH094 (3.33%), AS661463 (2.67%), and AS661231 (2.67%), which can be used in breeding programs to enhance BP resistance. We identified 11 QTL, which explained 8.22% to 10.99% phenotypic BP variation and mapped them to eight wheat chromosomes. Three of the QTL were novel. The molecular markers for the BP resistance could facilitate molecular breeding for developing BP resistant cultivars.

Black point of winter wheat seeds

Goal. To study infection of seeds of winter wheat varieties by «black point» and to establish the phytopathogenic composition of pathogens in the Right Bank Forest-Steppe of Ukraine. Methods. Laboratory — macroscopic analysis was performed according to DSTU 4138-2002, phytopathogenic composition was identified using nutrient medium, statistical analysis of the obtained data — calculation of the degree of pathogen severity, LSD. Results. A collection of 27 varieties of soft winter wheat was studied to determine the degree of seed infection. The highest percentage of infection was found in varieties Vodogray Bilotserkivsky (Ukraine), Adele (Russia), Balitus (Austria), Viglanka (Slovakia), Sefeg-2 (Azerbaijan). The least susceptible to the disease are varieties Daria (Croatia), Bodycek (France), Gratsia Bilotserkivska (Ukraine, Bila Tserkva DSS), Azano (Sweden), Gospodarka (Ukraine), Kozyr (Ukraine), Morozko (Russia), the number of grains with signs of darkening in the embryonic zone for these varieties did not exceed 1%. The sowing qualities of the diseased seeds were determined. The species composition of phytopathogens that cause the disease has been established. The phytopathogenic complex of seeds with the «black point» included fungi of the genera Alternaria, Fusarium, Curvularia, Bipolaris, Aspergillus, Acremoniella, Stemphillium, Sordaria and Epicoccum. Most often, the seeds were colonized by fungi of the genus Alternaria Nees. Their share in the years of research was 76.6—83.1%. Conclusions. The infection of seeds of winter wheat varieties by black point under conditions of the Right-Bank Forest-Steppe of Ukraine in 2018—2019 ranged from 0 to 19.8% depending on the variety and year of research. The phytopathogenic complex included 13 species of fungi from 9 genera: Alternaria, Fusarium, Curvularia, Bipolaris, Aspergillus, Acremoniella, Stemphillium, Sordaria, Epicoccum. The part of Alternaria spp. in the years of research was over 75%, the most common species were A. tenuissima and A. infectoria. The percentage of species from other genera was insignificant and did not exceed 4.6%.

Fetal Congenital Anomalies in Africa: Diagnostic and Management Challenges

There is paucity of knowledge on the causes, diagnosis, management and prevention of fetal congenital anomalies in Africa. The chapter will highlight on the general causes and specific factors concerning congenital anomalies in Africa. The problems of diagnosis and management of congenital anomalies will be extensively discussed. There is also going to be a discussion on how fetal anomalies contribute to maternal and perinatal mortality and morbidity. Screening of congenital anomalies is another black point and will be discussed emphasizing on simple strategies applicable in resource constrained environment. A section will be dedicated on prevention of fetal congenital anomalies, particularly prevention of specific factors that increase the risk of fetal anomalies in Africa. Finally, there will also be discussion on collaborative care as a panacea in the management of fetal congenital fetal anomalies, including my experience in this area. Specific examples will be given to illustrate the utility of collaborative in resource limited countries.

Molecular Mapping and Characterization of QBp.caas-3BL for Black Point Resistance in Wheat (Triticum Aestivum L.)

Wheat black point, which occurs in most wheat growing regions of the world, is detrimental to grain appearance, processing and nutrient quality. Mining and characterization of genetic loci for black point resistance is helpful for breeding resistant wheat cultivars. We previously identified a major QTL QBp.caas-3BL in a recombinant inbred line (RIL) population of Linmai 2/Zhong 892 across five environments. Here we confirmed the QTL in two additional environments. The genetic region of QBp.caas-3BL was enriched with newly developed markers. Using four sets of near isogenic lines QBp.caas-3BL was narrowed down to a physical interval of approximately 1.7 Mb, including five annotated genes according to IWGSC reference genome. TraesCS3B02G404300, TraesCS3B02G404600 and TraesCS3B02G404700 were predicted as candidate genes based on the analyses of sequence polymorphisms and differential expression. We also converted a SNP of TraesCS3B02G404700 into a breeding-applicable KASP marker and verified its efficacy for marker-assisted breeding in a panel of germplasm. The findings not only lay a foundation for map-based cloning of QBp.caas-3BL but also provide a useful marker for selection of resistant cultivars genotypes in wheat breeding.

Transcriptome-based analysis of resistance mechanism to black point caused by Bipolaris sorokiniana in wheat

Black point is a cereal disease caused by complex pathogens, of which the pathogenicity of Bipolaris sorokiniana is the most serious in wheat. Resistance to black point is quantitative in nature, and thus the mechanism is poorly understood. We conducted a comparative transcriptome analysis to identify differentially expressed genes (DEGs) in black point-slightly susceptible and -highly susceptible wheat lines at different timepoints following B. sorokiniana inoculation. DEGs associated with photosynthesis were upregulated in black point-slightly susceptible lines. The top Gene Ontology enrichment terms for biological processes were oxidation–reduction, response to cold, salt stress, oxidative stress, and cadmium ion; terms for cellular component genes were mainly involved in plasma membrane and cytoplasmic membrane-bounded vesicle, whereas those for molecular function were heme binding and peroxidase activity. Moreover, activities of antioxidant enzymes superoxide dismutase, catalase, and peroxidase were higher in slightly susceptible lines than those in highly susceptible lines (except peroxidase 12–24 days post-inoculation). Thus, resistance to B. sorokiniana-caused black point in wheat was mainly related to counteracting oxidative stress, although the specific metabolic pathways require further study. This study presents new insights for understanding resistance mechanisms of selected wheat lines to black point.