Marcos Ventura Faria

The double haploid (DH) technique in maize ( Zea mays L.) relies on in vivo haploid induction, in which the identification of haploid seeds and seedlings represents a critical step in this technique that determines the efficiency of DH line production. This study aimed to evaluate the effects of endosperm texture, donor genotype, and inducer on putative haploid rates based on the R1-navajo ( R1-nj ) marker and the use of guard cell length and stomatal density as a tool to identify diploids among putative haploids. Eleven hybrids were assessed as donor genotypes and were pollinated with ten haploid inducers. The response was the number of putative haploid seeds based on R1-nj phenotype, evaluated across the total number of seeds. Previously classified seeds of two induced maize hybrids were grown, and epidermal impressions of the abaxial face of maize leaves were used to measure guard cell length (GCL) and stomatal density (SD). Plants were classified according to the real ploidy by the gold standard evaluation. The three-way cross inducer (UH400×UH401)×TAIL 9 achieved the highest putative haploid rate (PHR) with five donor hybrids. The magnitude of the differences presented for GCL and SD were sufficient for the efficiency in the classification of ploidy in maize by means of logistic regression. The AUC values obtained were 0.916 for GCL and 0.941 for SD, indicating that both tests under study can be integrated into maize breeding programs, which can be used for proper disposal of diploids among putative haploids.

Doubled haploid (DH) technology has been widely adopted in maize ( Zea mays L.) breeding programs due to its ability to reduce breeding cycle time and optimize costs. Early ploidy identification is essential for maximizing the efficiency of DH production, particularly prior to chromosome doubling. This study aimed to evaluate the use of maize seedling traits as a strategy for discriminating haploids and diploids derived from in vivo haploid induction. Three commercial maize hybrids were crossed with 10 haploid inducers, and seeds were initially classified using the R1‐navajo ( R1‐nj ) marker. Seedlings were germinated on paper rolls and, after 96 h under controlled conditions, were evaluated for coleoptile length (CL), radicle length (RL), coleoptile diameter (CD), radicle diameter (RD) and number of lateral seminal roots (NLSR). Subsequently, seedlings were transplanted to the field, and true ploidy was determined at flowering based on gold standard phenotypic evaluation of vigour and tassel fertility. All seedling traits presented significant effects of hybrid and ploidy level, with diploid plants exhibiting greater values than haploids for the morphological traits. A random forest classifier integrating all seedling traits achieved a high area under the ROC curve (AUC) (0.892), accuracy (0.812), sensitivity (0.788) and specificity (0.858) for the overall model, englobing all three hybrids in a repeated stratified cross‐validation scheme. The error rates for the overall model were 8.4% for false discovery rate (FDR) and 21.2% for false negative rate (FNR), showing that the model was more effective at identifying true diploid seedlings. These results demonstrate that seedling phenotyping, when used integrated with machine learning, provides a complementary tool for early ploidy identification, improving efficiency of resource use in maize DH breeding programs.

Despite their economic relevance, studies on the physical, chemical, and sensory traits of green corn are still scarce. Therefore, this work aimed to identify superior hybrid combinations for post-harvest traits. For this purpose, 36 genotypes were evaluated in two different seasons, including 34 experimental hybrids and 2 testers (AG1051 and FT2015). AG1051 is a double hybrid of green corn, and FT2015 is a single hybrid of sweet corn. pH and °Brix in raw and cooked grains and weight loss were evaluated. It is concluded that there are promising crosses for the evaluated post-harvest traits. The crosses L111 x FT2015 and L33 x FT2015 showed high °Brix values in raw (means of 9.83 and 7.00) and cooked (means of 8.08 and 7.08) grains, low pH values in raw (means of 7.21 and 7.29) and cooked (means of 7.04 and 7.22) grains, and low weight loss (means of 1.66 g and 1.49 g).

Corn bacterial leaf streak is an emerging disease, and there are few studies related to its management. Therefore, it is necessary to know alternative hosts of this pathogen that may interfere with its survival during the off-season. The aim of this work was to evaluate different genotypes of oats, barley, and wheat as secondary hosts to the pathogen Xanthomonas vasicola pv. vasculorum. The experiments were carried out in Guarapuava, PR, Brazil, in the 2019 and 2022 seasons, in a greenhouse, with completely randomized design and five replications. Eight different cultivars of winter cereals widespread in the region were inoculated, and susceptible corn hybrid was used as a control. Disease incidence evaluations were performed to calculate the area under the disease progress curve (AUDPC). In the 2019 season, relative humidity averages at ten days after inoculation were between 54 and 68%, and only TBIO Audaz wheat cultivar, in addition to the control, showed symptoms related to the disease. In the 2022 season, when relative humidity remained around 70% throughout the experiment, all genotypes tested showed symptoms. However, cultivars Danielle (barley), TBIO Audaz, and ORS Vintecinco (wheat) did not differ from the susceptible corn control, with the highest AUDPC values. These results indicated that winter cereals are hosts of X. vasicola pv. vasculorum, and that relative humidity affects the expression of disease symptoms.

Low phosphorus (P) availability in tropical soils is one of the main constraints to agricultural productivity and the sustainability of cropping systems. In this study, we evaluated the functional potential of four bacterial strains, including those present in two commercial inoculants: Nodubiophos (Ag87-CCT 8090 and Ag94-CCT 8108), and Biomaphos (B119 and B2084), focusing on their production of phosphatase and phytase enzymes, organic acids, and their agronomic efficacy in soybean cultivation. In vitro assays showed that all strains exhibited phytase and both acid and alkaline phosphatase activities, with B2084 and Ag94 standing out in phytase-mediated mineralization. In contrast, B119 and B2084 showed the highest phosphatase activity. Organic acid production varied among strains and was influenced by the phosphate source, indicating a highly responsive metabolic regulation. Strains Ag87 and Ag94 were particularly effective in producing lactic, malic, and gluconic acids, displaying distinct profiles modulated by the available P source. In field trials, combined inoculation with Ag87 and Ag94 led to increased soybean yield, achieving performance comparable to conventional fertilization at 50% and 100% of the recommended P rate, despite applying only 30% of the total P. The results highlight complementary metabolic strategies among the evaluated strains, with the ability to solubilize and mineralize phosphorus through different mechanisms. They support their potential use as bioinoculants to enhance nutrient use efficiency and reduce fertilizer dependency in soybean cultivation.

Corn plant components play a key role in determining silage quality and yield. The aim of this work was to assess the importance of the structural component of the plant and grain in defining whole plant quality, thereby supporting the selection of topcross maize hybrids for silage. Eighty-four topcross hybrids were evaluated at the silage point. The qualitative traits of forage evaluated were the neutral detergent fiber of the whole plant (NDF-WP), acid detergent fiber of the whole plant (ADF-WP), lignin of the whole plant (LIG-WP), dry mass digestibility of the whole plant (DIG-WP), neutral detergent fiber of the plant without ear (NDF-WE), acid detergent fiber of the plant without ear (ADF-WE), lignin of the plant without ear (LIG-WE) and dry mass digestibility of the plant without ear (DIG-WE). The data were subjected to a joint analysis of variance; the genotypic correlation coefficients between traits were estimated, and a path analysis was conducted. The means of selected hybrids for NDF ranged from 51 to 60 %, for NDF-WE from 69 to 75 %, for ADF-WP from 25 to 32 %, for ADF-WE from 41 to 47 %, for DIG-WP from 51 to 63 %, for DIG-WE from 45 to 52 % and the yield at the silage point ranged from 11 to 16 t ha–1. The DIG-WE and grain vitreousness can be used for selecting genotypes with high digestibility of dry mass yield (DDMY) and high quality fiber. However, when the fiber quality of the vegetative parts is low, grain traits become the primary determinant of DDMY.

The objectives were to evaluate genetic divergence in 59 Solanum lycopersicum var. cerasiforme lines correlating with the country of origin, and to estimate the combining ability of 13 selected lines based on high soluble solids contents (°Brix). The DNA of the 59 lines was amplified using nine inter-simple sequence repeat (ISSR) primers. Shannon’s diversity index (I = 0.47) and Nei’s genetic diversity (h = 0.30) indicated high genetic diversity. Genetic differentiation coefficient (G_ST) = 0.035 suggested low genetic differentiation between populations and analysis of molecular variance (AMOVA) showed that high variability was not confined to any single country of origin. Principal coordinates analysis (PCoA) clustered the genotypes into three main groups, and a dendrogram confirmed no apparent relationship between the origin and the genetic profiles of the lines. Genetic classification of the mini tomato lines based on their country of origin is not feasible using ISSR markers. The 78 hybrids obtained from the crosses among the 13 selected lines were evaluated in a complete diallel scheme over two seasons, considering the number of bunches, number of fruits per bunch, average fruit weight, fruit length and width, peduncular scar, °Brix, productive cycle, and yield. Average fruit weight and yield were the traits that most influenced the genetic diversity of these 13 parental lines. Based on general combining ability (GCA) we identified lines with good performance for each trait, while specific combining ability (SCA) revealed crosses that exhibited outstanding performance. Promising lines and hybrids were selected for mini tomato breeding program advancement.

Damage caused by diseases, pests, or adverse weather conditions in the reproductive stages of corn crops results in reduced grain yield. However, studying the contribution of leaves in new hybrids is an alternative that makes it possible to reduce this damage. Therefore, this study aimed to contrast the effect of artificial defoliation at the R1 stage on the agronomic traits of four corn hybrids in a high-altitude region in two sowing seasons. The experimental design was randomized blocks in a 4 × 4 × 2 factorial scheme, referring to four defoliation levels (1- no removal of the leaf blade; 2- removal of all leaves; 3- removal of all leaves above the ear, and 4- removal of all leaves below the ear) × four hybrids (P1225 VYH, P3016 VYHR, DKB 345 PRO3, and P4285 VYHR) x two sowing dates (October and November), with four replicates. The loss of leaf area above the ear decreases the number of grains per ear by 19.5%, 1000-grain weight by 11%, and grain yield by 44.5% for the hybrids and sowing seasons studied in a high-altitude region. Grain yield was increased by sowing in October by 23% compared to November. The hybrid DKB 345 PRO3 obtained the highest grain yield at all defoliation levels at the R1 stage under the conditions of Guarapuava, PR.

The objective of this work was to select experimental corn lines genetically resistant to the bacterial leaf streak caused by Xanthomonas vasicola pv. vasculorum, in two growing seasons. The treatments were carried out in an experimental randomized block design in the 2019/2020 and 2020/2021 growing seasons, under a covered environment, with open ventilation, with four replicates. Seven lines resistant to and seven susceptible to foliar diseases were evaluated, in addition to two commercial hybrids used as checks. At the corn flowering stage, an artificial inoculation containing 3.78x10¹⁰ CFU mL⁻¹ of bacterial suspension was performed, and disease incidence and severity were assessed, based on a diagrammatic scale, every seven days. From these evaluations, the areas under the disease progress curve for each line were calculated, and individual and joint analyses of variance were performed. There is genetic variability among the corn genotypes for reaction to bacterial leaf streak, with a significant effect for the areas under the disease progress curve for incidence (AUDPCI) and severity (AUDPCS) between genotypes and between growing seasons, and for the genotype x season interaction. Lines LV1 and L14 are possible source genotypes for genetic resistance to the bacterial leaf streak.