Maize Genotypes Research Articles

Biochemical Study of maize (Zea mays L.) genotypes through total seed protein by SDS - PAGE

Maize (Zea mays L.) is one of the world's most important cereals, serving as a primary source of subsistence and industrial products. The remarkable phenotypic diversity exhibited by different maize genotypes depends on their complex biochemical compositions. In pursuit of a deeper understanding of the genetics and biochemistry of maize, this research explores the overall seed protein profiles of diverse maize genotypes using Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE). Primary objectives include comprehensive analysis and comparison of total seed protein composition between distinct maize genotypes, identification of protein differences associated with phenotypic differences, and insight into the genetic and environmental determinants of maize seed protein composition. Through state-of-the-art analytical techniques, including SDS-PAGE, This research examined protein supplements found in corn seeds. The results promise to reveal the genetic and environmental factors that shape the biochemistry of corn. The patterns of the total protein gave a number of 12 main bands, whose weights ranged between 17 kDa and 245 kDa. The total number of bands reached 108 bands, including 8 homogeneous bands and 6 heterogeneous bands. . The percentage of variation (difference) between the compositions was 32%, which indicates that the percentage of similarity (similarity) was 68%. The level of similarity is higher than the level of dissimilarity between the studied structures and this is due to the geographical origin of the structures and their genetic material, or that the plant is the result of hybridization between species, which ultimately benefits humanity’s quest to achieve sustainable agriculture and improved nutrition.

Nutrient and Microbiome-Mediated Plant-Soil Feedback in Domesticated and Wild Andropogoneae: Implications for Agroecosystems.

Plants influence the abiotic and biotic environment of the rhizosphere, affecting plant performance through plant-soil feedback (PSF). We compared the strength of nutrient and microbe-mediated PSF and its implications for plant performance in domesticated and wild grasses with a fully crossed greenhouse PSF experiment using four inbred maize genotypes (Zea mays ssp. mays b58, B73-wt, B73-rth3, and HP301), teosinte (Z. mays ssp. parviglumis), and two wild prairie grasses (Andropogon gerardii and Tripsacum dactyloides) to condition soils for three feedback species (maize B73-wt, teosinte, Andropogon gerardii). We found evidence of negative PSF based on growth, phenotypic traits, and foliar nutrient concentrations for maize B73-wt, which grew slower in maize-conditioned soil than prairie grass-conditioned soil. In contrast, teosinte and A. gerardii showed few consistent feedback responses. Both rhizobiome and nutrient-mediated mechanisms were implicated in PSF. Based on 16S rRNA gene amplicon sequencing, the rhizosphere bacterial community composition differed significantly after conditioning by prairie grass and maize plants, and the final soil nutrients were significantly influenced by conditioning, more so than by the feedback plants. These results suggest PSF-mediated soil domestication in agricultural settings can develop quickly and reduce crop productivity mediated by PSF involving changes to both the soil rhizobiomes and nutrient availability.

Altered fatty acid composition confers improved drought acclimation in maize

Drought induces alteration in membrane lipid composition in plants; however, still little is known about whether membrane lipid remodeling plays a role in plant drought acclimation, including both drought tolerance and recovery, especially in crops. Here, we imposed natural progressive drought and re-watering in 18 maize genotypes at the seedling stage, and analyzed the physiological responses, drought tolerance and drought acclimation capabilities, contents of lipids, and fatty acid compositions. The results showed that drought caused significant reductions in shoot dry weight, relative water content, Fv/Fm, total lipid content, and double bond index (DBI) in most genotypes, while re-watering partially recovered these reductions. Meanwhile, the total lipid content, fatty acid composition, and DBI were also changed obviously in response to drought and re-watering. In order to explore the relationship between membrane lipid change and plant drought response, we did a principal component analysis. The results showed that C18:3 fatty acid contributed greatly to drought tolerance, and C16:2 and C16:3 fatty acids were more responsible for drought recovery. Meanwhile, DBI showed significant positive correlations with shoot dry weight and relative water content, but a negative association with lipid peroxidation, and more importantly, DBI was important for both drought tolerance and recovery. These alterations in membrane lipid composition may facilitate increasing membrane fluidity and decreasing membrane damage, thus maintaining the high photosynthetic capability under drought. Our results suggest that lipid remodeling is important for drought tolerance and recovery in crops, and different fatty acid species have different roles in crop drought acclimation.

Macrospora leaf spot development conditions and resistance/tolerance of Brazilian commercially grown maize genotypes

Macrospora leaf spot (MLS), caused by the fungus Stenocarpella macrospora, is one of the most important diseases affecting maize in Brazil. However, there are no MLS-resistant cultivars commercially available. Therefore, this study aimed to investigate the lesion expansion rate of MLS in four maize genotypes, leaf wetness duration (0-, 6-, 12-, 18-, 24-, 30-, 36-, 42-, and 54-hour post-inoculation), disease development severity in three maize genotypes, and resistance/tolerance levels to MLS in 141 maize genotypes commercially grown in Brazil. The estimates were performed using logistic models adjusted to the parameters analyzed, except for resistance/tolerance levels, which were analyzed using proposed severity and resistance scales. The experiment was carried out at the Laboratory of Plant Phytopathology of the Epagri/Cepaf, Santa Catarina State, Brazil, from 2016 to 2020. Disease resistance was significantly different among genotypes and fungal isolates. However, none of the genotypes showed resistance or high tolerance levels to MLS. Leaf wetness duration influenced maximum disease severity, and lesion expansion rate differed significantly among the genotypes tested. All information generated in this study is essential for breeding programs of maize for MLS resistance

Standardisation of Temperature Induction Response Technique: A Promising Method for Screening of Maize Genotypes for Thermotolerance at Seed Level

Climate change adversely affects global agriculture. Heat stress is a major problem for crop production, which detrimentally affects plant growth and development. Maize is a diverse crop widely used as food, feed and fodder. Heat stress affects maize growth and development significantly, reducing the yield and quality of the crop. Crop improvement is critical for heat stress. With the advancement in omics technologies, developing tolerant genotypes has become a great option. The crop improvement involves screening and evaluation of the diverse maize genotypes, which is laborious and time-consuming. The temperature induction response technique (TIR) is one of the reliable and robust techniques that can be used for screening a large population of genotypes. It is based on the concept of acquired thermotolerance and lethal dose 50, but it is crop-specific. Hence, the present study standardized the TIR technique in maize at the seed level. The Lethal temperature standardised for maize seeds was 50°C for three hours, while the induction or sublethal temperature standardised was gradual exposure of maize seeds to 32-50°C for 4.5 hours. After a recovery period of 24 hours under room conditions, the seeds were tested for germination and recovery growth was measured as a means of thermotolerance. The standardized TIR in maize can be a reliable and robust technique for evaluating and screening the maize genotypes for thermotolerance at the seed stage itself.

Enabling genome editing in tropical maize lines through an improved, morphogenic regulator-assisted transformation protocol.

The recalcitrance exhibited by many maize (Zea mays) genotypes to traditional genetic transformation protocols poses a significant challenge to the large-scale application of genome editing (GE) in this major crop species. Although a few maize genotypes are widely used for genetic transformation, they prove unsuitable for agronomic tests in field trials or commercial applications. This challenge is exacerbated by the predominance of transformable maize lines adapted to temperate geographies, despite a considerable proportion of maize production occurring in the tropics. Ectopic expression of morphogenic regulators (MRs) stands out as a promising approach to overcome low efficiency and genotype dependency, aiming to achieve 'universal' transformation and GE capabilities in maize. Here, we report the successful GE of agronomically relevant tropical maize lines using a MR-based, Agrobacterium-mediated transformation protocol previously optimized for the B104 temperate inbred line. To this end, we used a CRISPR/Cas9-based construct aiming at the knockout of the VIRESCENT YELLOW-LIKE (VYL) gene, which results in an easily recognizable phenotype. Mutations at VYL were verified in protoplasts prepared from B104 and three tropical lines, regardless of the presence of a single nucleotide polymorphism (SNP) at the seed region of the VYL target site in two of the tropical lines. Three out of five tropical lines were amenable to transformation, with efficiencies reaching up to 6.63%. Remarkably, 97% of the recovered events presented indels at the target site, which were inherited by the next generation. We observed off-target activity of the CRISPR/Cas9-based construct towards the VYL paralog VYL-MODIFIER, which could be partly due to the expression of the WUSCHEL (WUS) MR. Our results demonstrate efficient GE of relevant tropical maize lines, expanding the current availability of GE-amenable genotypes of this major crop.

Agronomic performance of maize hybrids under Aspergillus flavus inoculation in Cameroon

Maize (Zea mays L.) is a major staple crop in most of the sub-Sahara Africa (SSA) region, constrained by a multitude of plant diseases, with the ear and kernel rots being the most widespread and difficult to manage on maize. The objective of this study was to access the agronomic performance of F1 maize hybrids exposed to Aspergillus flavus, under different agro-ecological conditions, in Cameroon. A total of 120 genotypes of maize, including four commercial hybrids, were evaluated under A. flavus infection at two sites; namely Bangangte in the Western Highlands and Mbalmayo, in the Bimodal Humid Forest Zone of Cameroon. The study was conducted during 2020 - 2021 cropping seasons. Results revealed that at Bangangte site, six (89343X88094, 88099X88094, 90204XExp 124, 89246X87036, TZI-5-1171XExp 124 and 90219X1368) out of the top 20 high yielding hybrids, had significantly high (p<0.001 tolerance (0% severity) to Aspergillus ear rot infection. At Mbalmayo site, eight (8923X88094, TZI-5-1171XExp124, 89343X88094, 90219X87036, 89243X87036, 87014X88094, TZSTR1150X87036 and 89248X88094) out of the top 20 high yielding hybrids also showed significant high (P<0.001) tolerance (0% severity) to Aspergillus ear rot infection. The interaction between hybrids and location was significant (P<0.05) for all measured traits, except ear height, grain texture, ear insect damage and husk cover (P>0.05). The pooled broad sense heritability of hybrids in the two locations varied from 5% for grain texture to 92% for days to 50% physiological maturity. Grain yield was negatively correlated with Aspergillus ear rot disease incidence and severity. Hence, promising high yielding maize hybrids with appreciable tolerance to Aspergillus ear rot disease could be selected among the tested genotypes.

Side Effects of Single-Transgene or Pyramided Genetically Modified Maize on the Generalist Endoparasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is an agricultural pest native to tropical and subtropical regions of the Americas, with considerable potential for global invasion and seasonal migration. Although genetically modified (GM) plants have shown positive impacts on the economy and the environment as they synthesize proteins that act as natural insecticides and are primarily intended to protect the crops from damage by specific pests, potential effects of Bt toxins on non-target organisms can occur. This experiment aimed to evaluate the potential impacts on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae), using the pupae of Spodoptera frugiperda (Lepidoptera: Noctuidae) as hosts, which were fed with transgenic maize genotypes such as Herculex®, expressing Cry1F protein, and PowerCore®, expressing Cry1F, Cry1A.105, and Cry2Ab2 proteins, or their non-transgenic isohybrid. The experiment was conducted in a completely randomized design with ten replicates. Spodoptera frugiperda larvae were fed ad libitum with transgenic and non-transgenic maize until the pupal stage and then individually exposed to six P. elaeisis females for 78 h. The total number of adults, emerged males, tibia size, cephalic capsule size, and parasitoid body size were not influenced by host feeding. However, the number of emerged females from the Herculex® and PowerCore® treatments was lower than that for the isohybrid treatment. The sex ratio and longevity of parasitoids emerging from PowerCore® were 1.05 and 1.26 times lower, respectively, than that of those from the isohybrid. Furthermore, the number of dead P. elaeisis within the host pupa was 10.56 times higher in the PowerCore® genotype. Combining Bt proteins within pyramided genotypes should cause minimal impacts and promote the conservation and integration of beneficial insects. The results of this study provide helpful information for developing effective and compatible integrated pest management (IPM) strategies.

Study of Genotypic and Phenotypic Correlation and Path Analysis Under Potassium Fertilization in Maize (Zea mays)

During the autumn season of 2018, a field experiment was carried out. The study’s goal was to evaluate phenotypic and genotypic correlation as well as path coefficient analysis under varied degrees of potassium fertilization. The study included nine different maize genotypes. Planted with three levels of potassium fertilization (75, 100, and 125 K2SO4 Kg Hectare-1). The split plot arrangement was done according to RCBD with three replications. The most important findings were summarized as follows: The genetic analysis revealed that genotypes differed significantly in all analyzed variables under the three levels of potassium fertilization. The grain yield genetically, phenotypically, and positively correlated with plant height, leaf area index, number of rows per ear, number of grain in a row and weight of 300 grain. The trait of a number of grains in a row showed genetic, phenotypic, and significant correlation with the three levels of potassium fertilization and the highest reached 0.95 and 0.89 respectively at the third level. Path analysis showed that the direct effects for a Leaf area index, number of rows per ear, Number of grains per row and weight of 300 grain were negative at the first level of potassium and highly positive at the other two levels. the direct selection for a number of rows per ear and Number of grains per row will incredibly effective in enhancing yield. However, the highest indirect effect for Number of grains per row was through plant height (1.76) at the first levels of potassium fertilization.

Proteomics Analysis Reveals Hormone Metabolic Process Involved in the Regulation of Kernel Water Content Induced by Exogenous Abscisic Acid in Maize

The water content of maize kernels during harvest is a critical factor influencing grain harvest practices globally. Abscisic acid (ABA) plays a pivotal role in grain development during the grain-filling process. Yet, there has been limited reporting on the regulatory mechanism of grain dehydration induced by exogenous ABA using proteomic techniques. In this study, two maize genotypes with distinct dehydration rates, DK517 (fast dehydration) and ZD1002 (slow dehydration), were treated with ABA after the heading stage. Results revealed a 20% lower yield in DK517 compared to ZD1002 following ABA application. Sixty days after pollination, the grain water content decreased to 23.55% in DK517 and 30.42% in ZD1002 due to ABA treatment. Through proteomic analysis, 861 and 118 differentially expressed proteins (DAPs) were identified in DK517 and ZD1002, respectively, as a result of ABA treatment. GO analysis indicated that the primary metabolic process, nitrogen compound metabolic process, and hormone metabolic process were significantly enriched among the DAPs in DK517 induced by ABA, while these pathways were absent in ZD1002. Twenty-four and fifteen overlapping DAPs showed contrasting responses in the two maize genotypes after ABA treatment. Notably, the expression levels of six known ABA signaling genes, including SnRK2 and DRE-like proteins, were downregulated in DK517 but remained unaltered in ZD1002 following ABA application. These findings underscore the distinct effects of exogenous ABA on the grain-filling characteristics of different maize genotypes, emphasizing the importance of the hormone metabolic process in regulating kernel water content induced by exogenous abscisic acid in maize.

Maize genotypes regulate the feedbacks between maize nitrogen uptake and soil nitrogen transformations

Maize (Zea mays L.) genotypes can directly affect gene expression and nitrogen (N) uptake capacity. However, the feedback between maize genotypes and soil gross N transformations, and their regulations on N uptake capacity are not well known. So, 15N tracing pot experiments were conducted in an acidic soil and an alkaline soil with six maize genotypes, i.e. Dika 007 (DK), Zhengda 999 (ZD1), Zhengdan 958 (ZD2), Jingke 968 (JK), Longdan 339 (LD), Liangyu 99 (LY). Maize N uptake and soil gross N transformation rates were quantified by the Ntraceplant tool to identify feedbacks between maize genotypes N uptake and soil N transformations and their mechanisms. Maize total N uptake rates (UTN) varied among genotypes and soils. UTN in alkaline soil was 1.1–2.1 times higher than that in acidic soil. NH4+ and NO3− uptake rates (UNH4 and UNO3, respectively) were regulated by specific N transport genes in acidic soil, supported by positive relationships between N uptake rates and relative expression of ZmNRT1.1, ZmNRT1.2 and ZmAMT1.1A genes. UTN, and UNO3 were positively correlated to soil gross N mineralization (M), and autotrophic nitrification (ONH4) rates, respectively. However, maize inhibited M compared to treatment without maize plantation (CK) due to effects on soil microbial community, and based on random forest analysis, the declined relative abundance of Acidicaldub, Gonytrichum and Nigrospora in acidic soil, Taeniolella in alkaline soil may cause the decrease of M by the presence of maize. Meanwhile, maize inhibited ONH4 to increase NH4+ residence time, which in turn was responsible for the positive relationship between UNH4 and ONH4. In contrast, the stimulation of heterotrophic nitrification (ONrec) by plants improved the NO3− availability. The maize genotypes, such as JK, could largely enhance N uptake by regulating the expression level of N transport genes in maize and stimulating soil N transformation to produce more inorganic N (Nmin) in the different soils. Our findings show that maize genotypes play a central role in regulating these feedbacks. These results are important for maize breeding and enhancing maize production.

Interactions between root hairs and the soil microbial community affect the growth of maize seedlings.

Root hairs are considered important for rhizosphere formation, which affects root system functioning. Through interactions with soil microorganisms mediated by root exudation, root hairs may affect the phenotypes and growth of young plants. We tested this hypothesis by integrating results from two experiments: (1) a factorial greenhouse seedling experiment with Zea mays B73-wt and its root-hairless mutant, B73-rth3, grown in live and autoclaved soil, quantifying 15 phenotypic traits, seven growth rates, and soil microbiomes and (2) a semi-hydroponic system quantifying root exudation of maize genotypes. Possibly as compensation for lacking root hairs, B73-rth3 seedlings allocated more biomass to roots and grew slower than B73-wt seedlings in live soil, whereas B73-wt seedlings grew slowest in autoclaved soil, suggesting root hairs can be costly and their benefits were realized with more complete soil microbial assemblages. There were substantial differences in root exudation between genotypes and in rhizosphere versus non-rhizosphere microbiomes. The microbial taxa enriched in the presence of root hairs generally enhanced growth compared to taxa enriched in their absence. Our findings suggest the root hairs' adaptive valueextends to plant-microbe interactions mediated byroot exudates, affecting plant phenotypes, and ultimately, growth.

Multilocus functional characterization of indigenous and exotic inbreds for dgat1-2, fatb, ge2 and wri1a genes affecting kernel oil and fatty acid profile in maize

Demand for maize oil is progressively increasing due to its diverse industrial applications, aside from its primary role in human nutrition and animal feed. Oil content and composition are two crucial determinants of maize oil in the international market. As kernel oil in maize is a complex quantitative trait, improving this trait presents a challenge for plant breeders and biotechnologists. Here, we characterized a set of 292 diverse maize inbreds of both indigenous and exotic origin by exploiting functional polymorphism of the dgat1-2, fatb, ge2, and wri1a genes governing kernel oil in maize. Genotyping using gene-based functional markers revealed a lower frequencies of dgat1-2 (0.15) and fatb (0.12) mutant alleles and a higher frequencies of wild-type alleles (Dgat1-2: 0.85; fatB: 0.88). The favorable wri1a allele was conserved across genotypes, while its wild-type allele (WRI1a) was not detected. In contrast, none of the genotypes possessed the ge2 favorable allele. The frequency of favorable alleles of both dgat1-2 and fatb decreased to 0.03 when considered together. Furthermore, pairwise protein-protein interactions among target gene products were conducted to understand the effect of one protein on another and their responses to kernel oil through functional enrichments. Thus, the identified maize genotypes with dgat1-2, fatb, and wri1a favourable alleles, along with insights gained through the protein-protein association network, serve as prominent and unique genetic resources for high-oil maize breeding programs. This is the first comprehensive report on the functional characterization of diverse genotypes at the molecular and protein levels.

Contamination of Fusarium spp. and mycotoxins at different ear physiological stages of maize in Argentina

Maize is one of the most important crops worldwide, being affected by several fungal species under field conditions. The study of plant-pathogen interaction plays a key role because fungal diseases are responsible for reducing grain yield and quality by increasing mycotoxin production. Thus, the present work aimed to evaluate the interaction of F. graminearum and F. verticillioides and mycotoxin production under field conditions along different physiological stages. During the 2019/2020 and 2020/2021 growing seasons, twelve maize genotypes were inoculated at the flowering stage (silking). Four treatments were applied using one isolate of each species: (i) F. graminearum; (ii) F. verticillioides; (iii) a combined inoculum (F. graminearum + F. verticillioides); (iv) and control treatment. Fungal diversity, disease evaluation, and mycotoxin contamination were evaluated at three different physiological stages: T1 (from R2 to R4), T2 (from R4 to R6), and T3 (at harvest time). A total of 15,907 Fusarium isolates were obtained. The results showed a predominance of F. verticillioides over F. graminearum in both years evaluated, reporting an increase in the occurrence of this species at late stages. Regarding mycotoxin contamination, no evidence was found supporting antagonism or synergism regarding isolates of both species used as inoculum under field conditions. The results reported in the present manuscript point out a major influence of climatic conditions on F. verticillioides predominance over F. graminearum, mainly during the late physiological stages. Furthermore, no clear relationship between mycotoxin concentration and physiological stages was established, suggesting that other grain factors, such as water activity and pH, could modulate mycotoxin production and accumulation under field conditions.

The influence of planting window on yield stability of maize genotypes in semi-arid areas

Maize is one of the most important field crops for feed, food, and raw material in South Africa. It is the main staple food for the majority of the people impoverished households in South Africa. Maize is susceptible to drought, and erratic rainfall and extreme climate variation are major maize production constraints in South Africa. This study aimed to determine the influence of planting dates on the grain yield stability of six maize genotypes in five environments for three (2019/20 to 2021/22) consecutive seasons. The additive main effect and multiplicative interaction (AMMI) model indicated that the environment contributed 59.20 % and 47.76 % of the total variation in grain yield at planting dates one (PD1) and two (PD2), respectively. The magnitudes of the genotype x environment interaction sum of squares were 5.20 for PD1 and 12.30 for PD2 times that of the genotype (genotype) sum of squares for the grain yield (GEI). The first principal component accounted for 53.14 % (PD1) and 47.76 % (PD2) of the total variation in the dataset. The AMMI genotype superiority measure (Pi), genotype and genotype by environment interaction (GGE), yield stability index, and AMMI stability value analyses identified genotypes DKC75–65BR and DKC78–45BRGEN as stable and high yielding across environments and planting dates. Genotype DKC71–44B was the least stable at both planting dates. Bothaville (E7) for PD1 and Coligny 2021/22(E13) for PD2 had high yield potential and were favorable environments, whereas Potchefstroom 2019/20 and 2021/22 were the least favorable environments for PD1 and PD2, respectively.

Variability in cadmium stress tolerance among four maize genotypes: Impacts on plant physiology, root morphology, and chloroplast microstructure

Cadmium (Cd) is detrimental to both plants and humans. Maize (Zea mays L.) genotypes exhibit variations in Cd accumulations. This study examined variations in Cd accumulation and tolerance among four maize genotypes with contrasting root morphology. The four maize genotypes were cultivated in a semi-hydroponic system with three Cd concentrations (0, 10, 20 μmol L−1). The effects of Cd on plant growth and physiology were assessed 39 days after transplanting. Results showed that root characteristics were positively correlated with root Cd accumulation and the bioconcentration factor under Cd20 treatment. Genotypes Shengrui999 and Zhengdan958 exhibited higher total Cd content than Xundan29 and Zhongke11 under Cd20 conditions. Cd toxicity led to membrane degradation of chloroplast mesophyll cells, loosening and swelling of grana lamella, and reduced starch reserves. The greater tolerance of Shengrui999 and Zhengdan958 was contributed to factors such as root biomass, shallower root depth, higher Cd content, accumulation of osmolyte such as soluble protein, antioxidant activities such as catalase (CAT), and the presence of phytohormone gibberellic acid. The study establishes a link between root morphology, Cd accumulation, and tolerance in maize plants, as demonstrated by the higher Cd accumulation and shallower root system in Cd-tolerant genotypes. This research provides a foundation for breeding maize cultivars better suited for adaptation to moderate Cd-contaminated environments.

The Cultured Microbiome of Pollinated Maize Silks Shifts after Infection with Fusarium graminearum and Varies by Distance from the Site of Pathogen Inoculation.

Styles transmit pollen-derived sperm nuclei from pollen to ovules, but also transmit environmental pathogens. The microbiomes of styles are likely important for reproduction/disease, yet few studies exist. Whether style microbiome compositions are spatially responsive to pathogens is unknown. The maize pathogen Fusarium graminearum enters developing grain through the style (silk). We hypothesized that F. graminearum treatment shifts the cultured transmitting silk microbiome (TSM) compared to healthy silks in a distance-dependent manner. Another objective of the study was to culture microbes for future application. Bacteria were cultured from husk-covered silks of 14 F. graminearum-treated diverse maize genotypes, proximal (tip) and distal (base) to the F. graminearum inoculation site. Long-read 16S sequences from 398 isolates spanned 35 genera, 71 species, and 238 OTUs. More bacteria were cultured from F. graminearum-inoculated tips (271 isolates) versus base (127 isolates); healthy silks were balanced. F. graminearum caused a collapse in diversity of ~20-25% across multiple taxonomic levels. Some species were cultured exclusively or, more often, from F. graminearum-treated silks (e.g., Delftia acidovorans, Klebsiella aerogenes, K. grimontii, Pantoea ananatis, Stenotrophomonas pavanii). Overall, the results suggest that F. graminearum alters the TSM in a distance-dependent manner. Many isolates matched taxa that were previously identified using V4-MiSeq (core and F. graminearum-induced), but long-read sequencing clarified the taxonomy and uncovered greater diversity than was initially predicted (e.g., within Pantoea). These isolates represent the first comprehensive cultured collection from pathogen-treated maize silks to facilitate biocontrol efforts and microbial marker-assisted breeding.

Analyzing the Variability in Maize (Zea mays L.) Genotypes Using Principal Component Analysis under Varied Ecosystems

Maize is a cereal cross-pollinated crop which belongs to the family poaceae. It is grown over a wider range of environment than any other cereal crop. The present study was conducted to study genetic variability using principal component analysis. Twenty maize genotypes were used in the study. Ten characters viz., plant height, ear height, days to 50 % tasselling, days to 50 % silking, ASI, cob length, number of rows per cob, hundred seed weight, shelling percentage and yield were recorded for the study. In the PCA, four principal components exhibited eigen value more than 1.0 exhibiting 84.54 percent of the variability for the characters under irrigated conditions. The PC1 negative loadings for the flowering traits, viz., days to 50 % silking (-0.3886), ASI (-0.3233) and days to 50 % tasselling (-0.2972) and positive loadings with higher contribution from cob length (0.4033), no of rows per cob (0.3480) followed by shelling percentage were observed. Positive loadings were exhibited by days to tasselling (0.4780), plant height (0.4670) and hundred seed weight (0.4518) in PC2. In PC3 positive loadings for the characters viz., number of rows per cob (0.5338), ASI (0.5226) and cob length (0.3299) and negative loadings for the traits grain yield (-0.3815), ear height (-0.2658) and plant height (-0.2437) and in PC4 positive loadings for plant height (0.4953), ear height (0.2546) and negative loadings were shown by days to grain yield (-0.6632), shelling percentage (-0.3751), ASI (-0.2369) and 50 % silking (-0.0648) were observed. In rainfed conditions, the two principal components had eigen value of more than 1. Under normal irrigated condition, PC1 and PC2 had eigen value of 5.689 and 1.6439. Plant height (0.3866), cob length (0.3726), number of rows per cob (0.3551), shelling % (0.3196), grain yield (0.2941), and hundred seed weight (0.2847) contributed positively to PC1. PC 2 had highest positive contributions from days to 50 % tasselling (0.5676), days to 50 % silking (0.5249), shelling % (0.3885), hundred seed weight (0.3763) and grain yield (0.2007). Negative loadings were shown by ear height (-0.1356) and plant height (-0.0093). Positive loadings were contributed by days to 50 % tasselling (0.5676), Days to 50 % silking, shelling percentage (0.3885) and hundred grain weight (0.3763).

Agronomic strategies to enhance the early vigor and yield of maize. Part I: the role of seed applied biostimulant, hybrid and starter fertilization on rhizosphere bacteria profile and diversity.

The sustainable intensification of maize-based systems may reduce greenhouse-gas emissions and the excessive use of non-renewable inputs. Considering the key role that the microbiological fertility has on crop growth and resilience, it is worth of interest studying the role of cropping system on the rhizosphere bacterial communities, that affect soil health and biological soil fertility. In this work we monitored and characterized the diversity and composition of native rhizosphere bacterial communities during the early growth phases of two maize genotypes of different early vigor, using a nitrogen (N)-phosphorus (P) starter fertilization and a biostimulant seed treatment, in a growth chamber experiment, by polymerase chain reaction-denaturing gradient gel electrophoresis of partial 16S rRNA gene and amplicon sequencing. Cluster analyses showed that the biostimulant treatment affected the rhizosphere bacterial microbiota of the ordinary hybrid more than that of the early vigor, both at plant emergence and at the 5-leaf stage. Moreover, the diversity indices calculated from the community profiles, revealed significant effects of NP fertilization on richness and the estimated effective number of species (H2) in both maize genotypes, while the biostimulant had a positive effect on plant growth promoting community of the ordinary hybrid, both at the plant emergence and at the fifth leaf stage. Our data showed that maize genotype was the major factor shaping rhizosphere bacterial community composition suggesting that the root system of the two maize hybrids recruited a different microbiota. Moreover, for the first time, we identified at the species and genus level the predominant native bacteria associated with two maize hybrids differing for vigor. These results pave the way for further studies to be performed on the effects of cropping system and specific crop practices, considering also the application of biostimulants, on beneficial rhizosphere microorganisms.

Variability for kernel starch components in Indian maize germplasm and identification of polymorphic molecular marker for selected waxy maize genotypes

Variability for kernel starch components in Indian maize germplasm and identification of polymorphic molecular marker for selected waxy maize genotypes