The Use of DArTseq Technology to Identify Markers Related to the Heterosis Effects in Selected Traits in Maize

Genotype by year interaction and additive and epistasis gene effects for Fusarium stalk rot resistance in doubled haploid lines of maize (Zea mays L.)

Fusarium stalk rot is the main factor reducing the quality of maize grain and leads to significant yield losses, which that ranges from 20 to 100%, depending on the degree of infection and weather conditions. Understanding its genetic mechanism is key to improving grain quality and ultimate yield. An experiment with 26 doubled haploid (DH) lines of maize was conducted in the northern part of the Lower Silesia Province in Poland over a ten-year period (2013-2022). The study assessed resistance to Fusarium stalk rot. The objectives were to evaluate genotype-year interactions for resistance to Fusarium stalk rot in maize DH lines using the additive main effects and multiplicative interaction (AMMI) model, to select DH lines that are stable across all years of testing and specific to particular environmental conditions, and to estimate additive and epistatic effects. AMMI results demonstrated a significant effect of genotype, year, and their interaction on Fusarium stalk rot resistance. The KN16 line is recommended for inclusion in further research within the breeding program due to its excellent stability and high average resistance to Fusarium stalk rot. Estimates of additive gene action effects were statistically significant in each year of the study. Estimates of epistasis (total additive by additive interaction) effects for Fusarium stalk rot resistance were also statistically significant in all ten years of the study. Only in 2013 was the epistasis effect positive (0.168). These results indicate that achieving biological advances in resistance to Fusarium stalk rot should be an important focus of ongoing maize breeding programs.

Genome-wide association mapping in safflower (Carthamus tinctorius L.) for genetic dissection of drought tolerance using DArTseq markers

Understanding the genetic basis of drought tolerance in safflower (Carthamus tinctorius L.) is essential for developing resilient varieties. In this study, we performed a genome-wide association study (GWAS) using DArTseq markers to identify marker-trait associations (MTAs) linked to drought tolerance across 90 globally diverse safflower genotypes. These genotypes were evaluated under both rainfed (drought) and irrigated conditions over three consecutive years (2016-2018). Significant variation in seed yield and morphological traits was observed between genotypes and across environments, with notably reduced performance under rainfed conditions. A total of 66 MTAs were identified for key agronomic traits, including seed yield, 1000-seed weight, number of heads per plant, and days to maturity, with 45 MTAs showing significant associations with the stress-tolerance index (STI). Twelve MTAs were consistently detected across both stress and non-stress conditions, suggesting stable loci for breeding applications. BLAST searches indicated that several identified markers corresponded to genes involved in abiotic stress response, including biotin carboxylase, serine/threonine-protein kinase, and zinc finger domain proteins. The clustering of genotypes based on drought-tolerance coefficient (DC) and STI values grouped genotypes into drought-susceptible and drought-tolerant categories, with no strong correlation to geographic origin. These findings provide valuable insights into the genetic architecture of drought tolerance in safflower and highlight candidate loci for marker-assisted selection, supporting the development of drought-resilient varieties.

Transcriptomic Characterization of Genes Harboring Markers Linked to Maize Yield

BACKGROUND

It is currently believed that breeding priorities, including maize breeding, should focus on introducing varieties with greater utility value, specifically higher yields, into production. Global modern maize breeding relies on various molecular genetics techniques. Using the above mentioned technologies, we can identify regions of the genome that are associated with various phenotypic traits, including yield, which is of fundamental importance for understanding and manipulating these regions.

OBJECTIVES

The aim of the study was to analyze the expression of candidate genes associated with maize yield. To better understand the function of the analyzed genes in increasing maize yield, their expression in different organs and tissues was also assessed using publicly available transcriptome data.

METHODS

RT-qPCR analyses were performed using iTaq Universal SYBR Green Supermix (Bio-Rad, Hercules, CA, USA) and CFX96 Touch Real-Time PCR Detection System (Bio-Rad, Hercules, CA, USA). Each of the performed RT-qPCR experiments consisted of three biological replicates and three technical replicates, the results of which were averaged.

RESULTS

The research results allowed us to select three out of six candidate genes (cinnamoyl-CoA reductase 1-CCR1, aspartate aminotransferase-AAT and sucrose transporter 1-SUT1), which can significantly affect grain yield in maize. Not only our studies but also literature reports clearly indicate the participation of CCR1, AAT and SUT1 in the formation of yield. Identified molecular markers located within these genes can be used in breeding programs to select high yielding maize genotypes.

Extent and patterns of morphological and molecular genetic diversity and population structure of Nigerian Taro cultivars

BACKGROUND

Genetic diversity is crucial for conservation efforts as well as breeding programs targeted at the development of improved varieties. Taro, a climate-resilient crop, plays a vital role in the nutritional and economic livelihoods of many households in Nigeria, but its yield is very low due to inadequate genetic improvement efforts. A diversity assessment of Nigerian taro is therefore required to create a premise for its improvement in yield, quality and disease tolerance. In this study, the genetic diversity and population structure of 490 taro cultivars comprising two main gene pools: Dasheen (215) and Eddoe (275), collected from farmers and marketers across seven states in Nigeria was assessed using 3047 Diversity Array Technology single nucleotide polymorphism (DArT-SNP) markers. A subset of 114 taro cultivars, comprising 30 Dasheens and 84 Eddoes were further phenotyped using 24 agro-morphological descriptors.

RESULTS

Both phenotypic and molecular characterization revealed higher genetic diversity among the Eddoes than Dasheens. Estimates of gene flow (Nm = 0.353) revealed intermixing of cultivars among the States of collection, with the highest gene flow occurring between cultivars from Anambra and Ondo states and the lowest between Anambra and Kwara states. Population structure and Ward's minimum variance hierarchical cluster based on DArT-SNPs identified four groups, one comprising Dasheen and three comprising Eddoe cultivars. Hierarchical clustering based on phenotypic traits delineated three clusters. Variation between gene pools (49%) was higher than within gene pools (32%). Variation among States of collection was high (41%), while variation among individuals within gene pools (18%) and States of collection (19%) was relatively low. Correlation between phenotypic and genotypic diversity assessments was low (r = 0.01), indicating that both approaches were necessary for assessing genetic diversity in taro. However, genotypic assessment provided better information about genetic diversity of the taro cultivars.

CONCLUSION

This is the first study that represented germplasm collection across the major taro growing regions of Nigeria. The findings from this study based on agro-morphological characterization and DArT-SNP genotyping are critical for genetic characterization, conservation and breeding of taro in Nigeria, mainly initiating hybridization between the two genepools after careful assessment of ploidy levels of the accessions collected in this study. This will facilitate in developing improved taro varieties with desirable traits, such as higher yield, better disease resistance, and improved nutritional quality.

Identification of SNP and SilicoDArT Markers and Characterization of Their Linked Candidate Genes Associated with Maize Smut Resistance

The implementation of biological advancements in agricultural production is the response to the needs of the agricultural sector in the 21st century, enabling increased production and improved food quality. Biological progress in the maize breeding and seed industries is unique in terms of their social and ecological innovation aspects. It affects agricultural productivity and the adaptation of cultivated maize varieties to market demands and changing climate conditions without compromising the environment. Modern maize resistance breeding relies on a wide range of molecular genetic research techniques. These technologies enable the identification of genomic regions associated with maize smut resistance, which is crucial for characterizing and manipulating these regions. Therefore, the aim of this study was to identify molecular markers (SilicoDArT and SNP) linked to candidate genes responsible for maize smut resistance, utilizing next-generation sequencing, as well as association and physical mapping. By using next-generation sequencing (NGS) and statistical tools, the analyzed maize genotypes were divided into heterotic groups, which enabled the prediction of the hybrid formula in heterosis crosses. In addition, Illumina sequencing identified 60,436 SilicoDArT markers and 32,178 SNP markers (92,614 in total). For association mapping, 32,900 markers (26,234 SilicoDArT and 6666 SNP) meeting the criteria (MAF > 0.25 and the number of missing observations < 10%) were used. Among the selected markers, 61 were highly statistically significant (LOD > 2.3). Among the selected 61 highly statistically significant markers (LOD > 2.3), 10 were significantly associated with plant resistance to maize smut in two locations (Smolice and Kobierzyce). Of the 10 selected markers, 3 SilicoDArT (24016548, 2504588, 4578578) and 3 SNP (4779579, 2467511, 4584208) markers were located within genes. According to literature reports, of these six genes, three (ATAD3, EDM2, and CYP97A3) are characterized proteins that may play a role in the immune response that develops in response to corn smut infection. In the case of genotypes belonging to the same origin groups, markers linked to these genes can be used to select varieties resistant to corn smut. These markers will also be tested on genotypes belonging to other maize origin groups to demonstrate their universality.

Using NGS Technology and Association Mapping to Identify Candidate Genes Associated with Fusarium Stalk Rot Resistance

Stalk rot caused by Fusarium fungi is one of the most widespread and devastating diseases of maize, and the introduction of resistant genotypes is one of the most effective strategies for controlling the disease. Breeding genotypes with genetically determined resistance will also allow less use of crop protection products. The aim of the research was to identify molecular markers and associated candidate genes determining maize plant resistance to Fusarium stalk rot. The plant material for this study consisted of 122 maize hybrids. The experiment was conducted in two localities: Smolice and Kobierzyce. The Fusarium stalk rot values ranged from 1.65% (for genotype G01.10) to 31.18% (for genotype G03.07) in Kobierzyce and from 0.00% (for 58 genotypes) to 6.36% (G05.03) in Smolice. The analyzed genotypes were simultaneously subjected to next-generation sequencing using the Illumina platform. Illumina sequencing identified 60,436 SilicoDArT markers and 32,178 SNP markers (92,614 in total). For association mapping, 32,900 markers (26,234 SilicoDArT and 6666 SNP) meeting the criteria (MAF > 0.25 and the number of missing observations <10%) were used. The results of the observation of the degree of infection and sequencing were used for association mapping, which ultimately resulted in the selection of ten molecular markers important at both places. Among the identified markers, two SNP markers that are located inside candidate genes play an important role. Marker 4772836 is located inside the serine/threonine-protein kinase bsk3 gene, while marker 4765764 is located inside the histidine kinase 1 gene. Both genes can be associated with plant resistance to Fusarium stalk rot, and these genes can also be used in breeding programs to select resistant varieties.

Identification and Analysis of Candidate Genes Associated with Yield Structure Traits and Maize Yield Using Next-Generation Sequencing Technology

The main challenge of agriculture in the 21st century is the continuous increase in food production. In addition to ensuring food security, the goal of modern agriculture is the continued development and production of plant-derived biomaterials. Conventional plant breeding methods do not allow breeders to achieve satisfactory results in obtaining new varieties in a short time. Currently, advanced molecular biology tools play a significant role worldwide, markedly contributing to biological progress. The aim of this study was to identify new markers linked to candidate genes determining grain yield. Next-generation sequencing, gene association, and physical mapping were used to identify markers. An additional goal was to also optimize diagnostic procedures to identify molecular markers on reference materials. As a result of the conducted research, 19 SNP markers significantly associated with yield structure traits in maize were identified. Five of these markers (28629, 28625, 28640, 28649, and 29294) are located within genes that can be considered candidate genes associated with yield traits. For two markers (28639 and 29294), different amplification products were obtained on the electrophorograms. For marker 28629, a specific product of 189 bp was observed for genotypes 1, 4, and 10. For marker 29294, a specific product of 189 bp was observed for genotypes 1 and 10. Both markers can be used for the preliminary selection of well-yielding genotypes.