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Climate change is expected to intensify water restriction to crops, impacting on the yield potential of crops such as popcorn. This work aimed to evaluate the performance of 10 field cultivated popcorn inbred lines during two growing seasons, under well-watered (WW) and water stressed (WS) (ψsoil≥ −1.5 MPa) conditions. Water stress was applied by withholding irrigation in the phenological phase of male pre-anthesis. Additionally, two contrasting inbred lines, P7 (superior line) and L75 (low performer) were compared for grain yield (GY) and expanded popcorn volume (EPV), selected from previous studies, were tested under greenhouse conditions. In the field, no genotype x water condition x crop season (G×WC×CS) interaction was observed, whereas GY (−51%), EPV (−55%) and leaf greenness (SPAD index) measured 17 days after anthesis (DAA) (> −10%) were highly affected by water limitation. In general, root traits (angles, number, and density) presented G×WC×CS interaction, which did not support their use as selection parameters. In relation to leaf senescence, for both WS and WW conditions, the superior inbred lines maintained a stay-green condition (higher SPAD index) until physiological maturity, but maximum SPAD index values were observed later in WW (48.7 by 14 DAA) than in WS (43.9 by 7 DAA). Under both water conditions, negative associations were observed between SPAD index values 15 and 8 days before anthesis DBA), and GY and EPV (r ≥ −0.69), as well as between SPAD index 7, 17, and 22 DAA, and angles of brace root (AB), number of crown roots (NC) and crown root density (CD), in WS (r ≥ −0.69), and AB and CD, in WW (r ≥ −0.70). Lower NC and CD values may allow further root deepening in WS conditions. Under WS P7 maintained higher net photosynthesis values, stomatal conductance, and transpiration, than L75. Additionally, L75 exhibited a lower (i.e., more negative) carbon isotope composition value than P7 under WS, confirming a lower stomatal aperture in L75. In summary, besides leaf greenness, traits related to leaf photosynthetic status, and stomatal conductance were shown to be good indicators of the agronomic performance of popcorn under water constraint.

Southern corn leaf blight (SCLB), caused by the pathogen Bipolaris maydis, can cause significant damage to popcorn production. However, genetic resistance in maize germplasm offers a viable strategy for disease control. This work investigated the performance of popcorn lines for SCLB resistance and their potential for producing hybrids. Thirty-five lines were evaluated in two environments using a randomized block design with four replicates. Measurements of Bipolaris incidence (BI) and severity (BS) were taken 30 days after the beginning of flowering. Grain yield (GY) and popping expansion (PE) were evaluated at grain maturity. The data were analyzed using joint analysis of variance and the Scott-Knott test at a 5% significance level. Significant variation in all four parameters were observed for BI, BS, GY and PE, and the lines were grouped accordingly. Two lines with high levels of resistance to SCLB (L623 and L624) were identified. Five lines (L509, L204, L683, L292, L70) stand out as having high potential for breeding based on their levels of both popping expansion and SCLB resistance.

Popcorn is an important crop that is grown for consumption and snacks production in Nigeria however; it has low production and poor yield to meet the demand in the country. This study was conducted to determine the effect of magnetic treatment of irrigation water (MTIW) on the percentage germination (GP), growth rate (GR), popping-quality and yield of popcorn under deficit irrigation. MTIW was produced by passing the water through pipe surrounded with neodymium magnet rated 1.3 Tesla. Popcorn (FRESHTOP variety) was planted in 16 buckets for MTIW and 16 buckets for non-magnetic water (NMW, as control). Four levels of water application as the treatments with 100% water requirements (1.5 liters), 80% (1.2 liters), 60% (0.9 liters) and 50% (0.75 liters) were applied to the popcorn irrigated with MTIW or NMW and monitored for 100 days. The popcorn was thinned to 1 bucket-1 and grown in a garden shed of 5 by 5m and 3m high at the center and 2.5m at the edges. GP of the popcorn at 100%, 80%, 60% and 50% for MW were 75%, 88%, 75%, 63% and for NMW, were 50%, 63%, 50% and 50%, respectively. Mean grain yield after shelled for 100%, 80%%, 60% and 50% with MTIW were 43.43, 50.86, 39.65 and 35.80 g/bucket and corresponding grain yield for NMW were 29.20, 39.43, 37.27 and 28.41 gbucket-1. Water applied at 80% produced the highest yield. MTIW increased the yield of popcorn by 48.73%, 28.88%, 6.39% and 26.01% for 100%, 80%, 60% and 50%, respectively. MTIW is recommended for growing ‘FRESHTOP’ variety popcorn. 

The identification of the genes responsible for complex traits is highly promising to accelerate crop breeding, but such information is still limited for popcorn. Thus, in the present study, a mixed linear model-based association analysis (MLMA) was applied for six important popcorn traits: plant and ear height, 100-grain weight, popping expansion, grain yield and expanded popcorn volume per hectare. To this end, 196 plants of the open-pollinated popcorn population UENF-14 were sampled, selfed (S1), and then genotyped with a panel of 10,507 single nucleotide polymorphisms (SNPs) markers distributed throughout the genome. The six traits were studied under two environments [Campos dos Goytacazes-RJ (ENV1) and Itaocara-RJ (ENV2)] in an incomplete block design. Based on the phenotypic data of the S1 progenies and on the genetic characteristics of the parents, the MLMA was performed. Thereafter, genes annotated in the MaizeGDB platform were screened for potential linkage disequilibrium with the SNPs associated to the six evaluated traits. Overall, seven and eight genes were identified as associated with the traits in ENV1 and ENV2, respectively, and proteins encoded by these genes were evaluated for their function. The results obtained here contribute to increase knowledge on the genetic architecture of the six evaluated traits and might be used for marker-assisted selection in breeding programs.

Agricultural expansion and the need for sustainable cultivation are challenges faced by researchers involved in the generation of new cultivars that can adapt to abiotic stress. Knowledge of the genetic effects of characteristics related to efficiency and responsiveness to phosphorus use must be considered when implementing methods to obtain better genotypes. The aim of this study was to characterize and select popcorn hybrids based on their efficiency and responsiveness to phosphorus use, and estimate their combining abilities and genetic effects via diallel analysis to implement improvement programs for sustainable agriculture. Eight contrasting inbred lines were used to obtain simple hybrids for diallel analysis. Twenty-eight diallelic hybrids plus the popcorn parental lines were evaluated at two different sites under two contrasting environments for soil phosphorus availability (6 × 6 lattice design). Grain yield, popping expansion, and volume of expanded popcorn per hectare were measured. A combined analysis of variance and a test of means were performed. The classification and utilization of the phosphorus use efficiency index, according to the grain yield performance of the hybrids under contrasting environments, was considered. Through model 2 of the Griffing's diallel analysis method, the general and specific combining abilities were estimated, along with their environmental interactions. The best strategy to obtain genotypes that are efficient and responsive to phosphorus involves exploring popcorn hybrids using genitors that result in the accumulation of additive genes that promote popping expansion. Hybrids P7 × L80, P7 × L59, P7 × L76, and P6 × L80 presented promising results and may be evaluated as cultivation options in phosphorus-deficient soils.

Summary Kernel weight is a critical factor that essentially affects maize (Zea mays) yield. In natural inbred lines, popcorn kernels exhibit overtly smaller sizes compared to dent corn kernels, and kernel weight, which is controlled by multiple genetic loci, varies widely. Here, we characterized a major quantitative trait locus on chromosome 1, responsible for controlling kernel weight (qKW1) and size. The qKW1 locus encodes a protein containing a seven in absentia domain with E3 ubiquitin ligase activity, expressed prominently from the top to the middle region of the endosperm. The presence and function of qKW1 were confirmed through ZmKW1 gene editing, where the mutations in ZmKW1 within dent corn significantly increased kernel weight, consistent with alterations in kernel size, while overexpression of ZmKW1 had the opposite effect. ZmKW1 acts as a negative regulator of kernel weight and size by reducing both the number and size of the endosperm cells and impacting endosperm filling. Notably, the popcorn allele qKW1N and the dent corn allele qKW1D encode identical proteins; however, the differences in promoter activity arise due to the insertion of an Indel‐1346 sequence in the qKW1N promoter, resulting in higher expression levels compared to qKW1D, thus contributing to the variation in kernel weight and size between popcorn and dent corn kernels. Linkage disequilibrium analysis of the 2.8 kb promoter region of ZmKW1 in a dataset comprising 111 maize association panels identified two distinct haplotypes. Our results provide insight into the mechanisms underlying kernel development and yield regulation in dent corn and popcorn, with a specific focus on the role of the ubiquitination system.

Velvetleaf is an economically important weed in popcorn production fields in Nebraska. Many PRE herbicides in popcorn have limited residual activity or provide partial velvetleaf control. There are a limited number of herbicides applied POST in popcorn compared with field corn, necessitating the evaluation of POST herbicides for control of velvetleaf. The objectives of this study were to (1) evaluate the efficacy and crop safety of labeled POST herbicides for controlling velvetleaf that survived S-metolachlor/atrazine applied PRE and (2) determine the effect of velvetleaf height on POST herbicide efficacy, popcorn injury, and yield. Field experiments were conducted in 2018 and 2019 near Clay Center, Nebraska. The experiments were arranged in a split-plot design with four replications. The main plot treatments were velvetleaf height (≤15 cm and ≤30 cm) and subplot treatments included a no-POST herbicide control, and 11 POST herbicide programs. Fluthiacet-methyl, fluthiacet-methyl/mesotrione, carfentrazone-ethyl, dicamba, and dicamba/diflufenzopyr provided greater than 96% velvetleaf control 28 d after treatment (DAT), reduced velvetleaf density to fewer than 7 plants m–2, achieved 99% to 100% biomass reduction, and had no effect on popcorn yield. Herbicide programs tested in this study provided greater than 98% control of velvetleaf 28 DAT in 2019. Most POST herbicide programs in this study provided greater than 90% control of up to 15 cm and up to 30 cm velvetleaf and no differences between velvetleaf heights in density, biomass reduction, or popcorn yield were observed, except with topramezone and nicosulfuron/mesotrione 28 DAT in 2018. On the basis of contrast analysis, herbicide programs with fluthiacet-methyl or dicamba provided better control than herbicide programs without them at 28 DAT in 2018. It is concluded that POST herbicides are available for control of velvetleaf up to 30-cm tall in popcorn production fields. Nomenclature: Atrazine; carfentrazone-ethyl; dicamba; diflufenzopyr; fluthiacet-methyl; mesotrione; S-metolachlor; nicosulfuron; topramezone; velvetleaf; Abutilon theophrasti Medik; field corn, Zea mays L. var. indentata; popcorn, Zea mays L. var. everta

Drought is a common abiotic stress in tropical and subtropical regions that limits the growth and development of agricultural crops, mainly impacting grain yield. Acting through plant breeding is the most viable alternative for obtaining genotypes more tolerant of environments with stress. This work aims to select popcorn genotypes for environments with drought and to identify discriminating traits for the evaluation of drought tolerance in popcorn germplasm. Fifteen Latin American populations of popcorn were evaluated in water stress (WS) and well-watered (WW) conditions. The evaluated traits were based in morpho-agronomic, physiological and radicular descriptors. Data were submitted to individual and joint ANOVA and GT Biplot analysis. Variability was detected between populations for all traits in both conditions. The drought caused a reduction of 30.61% and 3.5% in grain yield and popping expansion, respectively. Based in GT biplot analysis, 880POP was the most stable in WS and WW, being indicated as a promising population for cultivation in environments with water limitation. This study is going to allow the establishment of a collection of great importance to maize germplasm and to provide information to facilitate the process of selection in breeding programs focused on drought tolerance.

The Northern corn leaf blight (NCLB) caused by the fungus Exserohilum turcicum is one of the oldest and most important leaf diseases of corn, occurring widely in Brazil and in the main producing regions of the world. The pathogen causes the devastating leaf disease that results in considerable losses in corn yield. The objective of this research was to identify genomic regions or associated SNPs involved in resistance to NCLB in a panel of field corn, popcorn, and sweet corn inbred lines. A genome-wide association study was carried out with phenotypic data collected in two environments on a panel of 320 maize inbred lines. The experiments were conducted in a 20 × 16 alpha-lattice experimental design, with three replications. The severity of NCLB was evaluated 25 days after the end of flowering. A set of 350, 643 high-quality polymorphic SNPs obtained using genotyping by sequencing were used, 14 of which were associated with E. turcicum resistance. The variation explained by each SNP ranged from 0.5 to 5.7%. In the first growing season, five SNPs explained 16.2% of the phenotypic variance, while during the second growing season, nine SNPs explained 16.5% of the total phenotypic variance. The candidate gene models GRMZM2G042920, GRMZM2G041774 and GRMZM2G056564 were the most promising, given that they were previously identified playing an important role in the response of corn to defense, abiotic and biotic stress through signaling mechanisms.

The current popcorn production in Mexico is insufficient to meet the demand for this grain, since there are no genotypes suitable for production within the country. The native popcorn varieties do not meet market standards; therefore, it is necessary to carry out genetic improvement on yield and popping expansion. The objective of this study was to estimate the response to selection on yield and popping expansion of popcorn under two modalities of mass selection. We used a population of popcorn from the first selection cycle (C1) of the cross between a commercial popcorn of the North American Yellow Pearl race and a native population of the Mexican race Palomero Toluqueño. An additional cycle of mass selection (C2) was carried out with stratification (MSS) and without stratification (MNSS) followed by a field trial that included the different cycles of selection. The parents of the initial cross and two controls, under a complete randomized block experimental design with 10 replications in two localities, and the genetic gain per cycle was calculated. Genotypes C2MSS, C2MNSS, C1MSS and the control Palomero Ixtenco showed the highest average grain yield with values of 4.9 t ha−1. For popping expansion, the Jack Superior control showed the best flake volume with 34.7 cm3 g−1, in contrast to the native popcorn Criollo Plaza with a value as low as 7.2 cm3 g−1. Chapingo was the locality with the highest grain yield, averaging 5.08 t ha−1, while in San Salvador Atenco, the yield was 2.78 t ha−1. Genetic gains were found with a popping expansion of 12.50% with stratification and 11.42% without stratification. For grain yield, a gain of 6.82% was obtained using stratification and 0.74% without stratification. Stratified visual mass selection is an efficient method for genetic advancement in popcorn yield, while popping mass selection is efficient regardless of stratification.