Introduction. The availability of water for agricultural production is essential. The production of corn, subject to the rainy season, in Mexico exceeds 70%. In the agricultural regions of the Yucatan, productions are reported in conditions of low rainfall or very erratic precipitation, which can cause total losses. A critical condition for the establishment of a crop is to have the necessary humidity that allows germination. Objective. The aim of the present work was to evaluate maize materials under simulated water stress conditions through osmotic solutions in order to identify those that can tolerate these conditions. Materials and methods. The study was carried out in the Campo Experimental Mococha of the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, during 2017; including the germination and establishment phase. Twenty-five maize materials were used under a completely random design with a factorial arrangement. A germination test was performed under simulated two stress conditions by means of the PEG 8000 (-0.50 and -0,75 MPa), also a control (0 MPa) was used. Four replicates of twenty-five seeds were done. The seeds were exposed for 24 h to the PEG 8000, subsequent, irrigations were done with distilled water. The seeds were exposed for 24 h to PEG 8000, later, the seeds were irrigated with distilled water. The germinated seeds were counted on the seventh day and reported as germination percentage. In a sample, of ten seedlings of each repetition, length and weight were measured, separately, from the aerial part and the root. Results. From the evaluated materials, the hybrids H-563, H-565 and H-568 endured a stress of -0.5 MPa, and the H-520, H-567 and HEV3B hybrids presented germination with -0.75 MPa and stood out in all the variables evaluated. Conclusion. It is possible to identify materials that will tolerate stress conditions during the germination stage.

The elongation of the mesocotyl and the coleoptile and other seedling traits were analyzed from 16 hybrids of two seed sizes, five varieties and a control. Sowing was conducted in sand beds during the S-F 2020 cycle, where nine genotypes were identified that differed in the elongation of the mesocotyl: long (H-48, HS-2 and Promesa); medium (H-44-H-52 and H-70); and short (H-49 AE, H-40 and H-32). A total of 36 possible crosses were obtained between these nine parents, which were established in the S-S 2021 cycle, and on sand beds. Results show that seed size affected (p< 0.05) the speed and percentage of emergence, the elongation of mesocotyl–coleoptile, the biomass and the heterosis in parents and their crosses. The H-48 hybrid presented greater speed and percentage of emergence and elongation of the mesocotyl and the coleoptile with both seed sizes. The highest dry weight of mesocotyl, coleoptile, roots, and leaves was found in the hybrids Promesa and H-48. The crosses between parents with contrasting mesocotyl presented superior elongation and dry weight (p ≤ 0.05) compared to their parents, with the long × long (1 × 2, 1 × 3 and 2 × 3) crosses standing out for all the traits measured. A strong positive association was obtained (p ≤ 0.01) between the elongation of the mesocotyl–coleoptile, the percentage of emergence, and the production of total dry matter in parents and their crosses.

Introduction. The genus Cucurbita presents a wide diversity in Mexico, within the species that compose the genus have been selected for different purposes. This crop is an important part of the milpa complex in the Yucatan Peninsula. Objective. Evaluate some fruit and seed characteristics of six squash genotypes obtained in the Yucatan Peninsula from chihua squash. Materials and methods. Six collections of Cucurbita argyrosperma Huber, obtained in the Yucatan Peninsula, were evaluated in a randomized complete block design for two years. The number of fruits per plot, fruit weight and size, seed weight and number of total, empty and full-filled seeds per fruit and brix degrees of pulp were quantified. Results. Differences in fruit production were found between collections but not for years. The dominant fruit size was medium, fruits between 500 and 999 g, with the Chetumal collection standing out, while the variables of seed weight and number of seeds were affected between collections and between years, as a result of low rainfall during the production cycle of the second year, all collections recorded a reduction in weight and an increase in the number of empty seeds, with Yucatan rebounding. Slight variations were identified in the concentration of brix degrees in the pulp, with the Chetumal collection standing out above the rest. Conclusions. The evaluated collections present variability within them, which can be useful to select materials for different purposes and to obtain more benefits from this crop. Objective: To evaluate some fruit and seed characteristics of six chihua squash genotypes obtained in the Yucatan Peninsula. Materials and methods: Six collections of Cucurbita argyrosperma Huber, obtained in the Yucatan Peninsula, were evaluated in a randomized complete block design for two years. The number of fruits per plot, fruit weight and size, seed weight and number of total, empty and full-filled seeds per fruit were quantified, and degrees Brix of the pulp. Results: Differences in fruit production were found between collections. The dominant fruit size was medium, fruits between 500 and 999 g, with the Chetumal collection standing out, while the variables of seed weight and number of seeds were affected between collections and between years, because of low rainfall during the production cycle of the second year. All collections recorded a reduction in weight and an increase in the number of empty seeds. Slight variations were identified in the concentration of degrees Brix of the pulp, with the Chetumal collection standing out above the rest. Conclusions: The evaluated collections present variability within them, which can be useful to select materials for different purposes and to obtain more benefits from this crop

Corn germplasm with different mesocotyl elongation was characterized for High Valleys in Mexico by estimating the general combinatory aptitude (GCA), specific combinatory aptitude (SCA), heterosis (H), inbreeding depression (ID) and principal component aptitude (PCA), with the purpose of directing the improvement for deep sowing. The hypothesis was that the parents and crosses of mesocotyl present variability in seedling and adult plant traits based on deep sowing. The 36 F₁ and F₂ crosses—derived from nine parents, three with short mesocotyl (S), three medium (M) and three long (L), obtained through Griffing diallel II—plus the parents were planted in sand beds and polyethylene bags in a greenhouse during the spring–summer cycles of 2021 and 2022. The following traits were measured: length of mesocotyl (LM), length of coleoptile, total seedling dry matter and 10 cob traits in addition to total dry matter. In 11 of the 14 traits, there was a positive and significant correlation (p ≤ 0.05) between the GCA of the parents and their LM. The highest SCA, H and ID (p ≤ 0.05) were for crosses L × L for all the traits measured. When comparing the GCA/SCA proportions, this relation varied from 0.76 to 0.97, which points to practically equal additive effects with those of dominance; however, in parents and L × L crosses, this relation was on average 0.94, 1.07 in M × M, 0.22 in S × S and 0.36 in L × S. In both F₁ and F₂, the variation was explained by two principal components: 89.5% for GCA and 73.4% for SCA. In both generations, the parents with higher GCA were H-48, HS-2 and Promesa, the three with long mesocotyl, while those with the highest GCA were crosses between these three hybrids.

Haematoxylum campechianum L., conocido como palo de Campeche o palo de tinte y entre los pobladores mayas como éek, tooso boon che’ o palo, con alto valor comercial se encuentra creciendo como planta silvestre en la Península de Yucatán, esta especie es un taxón distribuido en la región, con valor con histórico, patrimonial y económico, debido a su comercialización como materia prima para extraer tinturas naturales. Los objetivos de esta investigación fueron determinar la morfometría, viabilidad y germinación de semillas de palo de tinte en campeche en función de la temperatura y periodo de almacenamiento, con la finalidad de incrementar su potencial de aprovechamiento forestal. Se recolectaron semillas en el municipio de Escárcega, Campeche, en el mes de marzo del año 2024. Se realizaron pruebas de germinación y viabilidad (prueba de tetrazolio) cada 30 días durante ocho meses, a diferentes temperaturas (-18 °C, 3 °C, 23 °C y temperatura ambiente ≈ de 31 °C). Se encontraron diferencias significativas (p< 0.05) del porcentaje de germinación (% G) de acuerdo con el tiempo de almacenamiento, donde el mayor porcentaje de germinación (90%) fue en la temperatura de 3 °C. La viabilidad se mantuvo durante 180 días, después fue disminuyendo gradualmente, por las características encontradas se infiere que las semillas de H. campechianum se clasifican como intermedias.

Objective: The effect of thermal and water stress on growth, biomass production and yield in native corn (Zea mays L.) was evaluated. Design/methodology/approach: The study grouped 17 native corn cultivars. Heat unit accumulation, leaf area growth, yield, total biomass dry weight, and other dry matter characteristics were evaluated. Individual analyses of variance and correlation were performed using SAS® statistical software. Means were compared using the Tukey test (P≤0.05). Results: The effect of thermal and water stress allowed to observe a significant variation in the growth of the leaf area and production of dry matter and yield of native corn; on average, better expression was obtained through the genotypes Saak dzit baakal and Kȁn Kȁn xnuc naal that presented greater growth, biomass and yield based on thermal and water stress. Limitations on study/implications: The study was limited to the application of water stress during the vegetative stage; it is suggested to cause stress during the reproductive stage. Findings/conclusions: The native corns Saak dzit baakal and Kȁn Kȁn xnuc naal showed greater tolerance to thermal and water stress by presenting greater acclimatization that allowed them to present greater growth, biomass production and grain yield.