Generation of the H74 hybrid

The corn hybrid Venado H74 generated from inbreds Mich 21 Comp.1-7-2-14-1-3 with level of inbreeding S₅, identified in its registry as M54 and Tlax. 151 SFC1-11-2-2-2 with inbreeding level S₄, registered as M55, both lines were generated by the pedigree method with per se selection. The origin of the M54 line is found in the creole variety called Michoacan 21, while that of the M55 line in the creole variety Tlaxcala-151. The crossing of these lines gave rise to the female progenitor M54 x M55. In the sources of germplasm Mich 21 and Tlax 151 there have been significant effects of general combinatorial aptitude (^{Balderrama et al., 1997}).

The CML456 line is also involved in the generation of this hybrid as a male parent, this was derived from the early pre-mature white population and has S₄ inbreeding level and three cycles of massive increase, this line was obtained by the International Center for the Improvement of Corn and Wheat (CIMMYT) and its genealogy is: (crosses simple high valleys of INIFAP x Batan 8585-6) -B-1-1-1-2-BTL-B, Batán 8585-6 comes from the population 85 precocious white semidetached. The combination of lines from sources Mich 21 and Tlax 151 by lines of the population 85 show favorable effects of specific combinatorial aptitude (^{Arellano, 1998}).

The process of derivation and selection of lines of the simple female crossbreed of the hybrid Venado H74 was carried out from 1946 to 1984. During the period from 1985 to 2009, experimental simple crosses of the female were obtained, evaluated and selected. The tri-linear hybrid Venado H74 was generated in 2009 and from 2010 to 2016, experimental evaluations and semi-commercial validation were carried out in localities of the High Valleys. In 2017, the documents required for official registration were submitted to the National Seed Inspection and Certification Service (SNICS).

In the Figure 1 shows the classical hybridization scheme for obtaining the hybrid Venado H74 from ears representative of the progenitors and the hybrid. It can be seen that the M54 progenitor is a small ear of conical type with round grain of semi-hardened texture and creamy color, while the M55 line is of long ear with irregular rows and thin pointed grain and semi-crystalline white. The crossing of both parents generates the female progenitor M55 X M54 that exhibits considerable heterosis in size and weight of the ear that is conical with grain of creamy white texture. While the male progenitor line CML456 has a small ear of conical shape with white semicrystalline type grain. The female parent when crossing with the male parent generates the combination that gave rise to the new trilinear hybrid Venado H74 of medium-sized cylindrical conical ear of regular rows with white semicrystalline type grain.

Figure 1 Schematic of obtaining the hybrid of early corn Venado H74 and phenotypic characteristics of the ears representative of the progenitors and the hybrid. 

Registration of the corn hybrid Venado H74 in the national catalog of plant varieties

Based on the Production, Certification and Seed Trade Act in force in Mexico and after having met the requirements for registration, the hybrid of Venado H74 corn was registered in 2017 in the National Catalog of Varieties of Vegetables (CNVV) with the Provisional registration number: 3567-MAZ-1884-310118 / C.

Description of the morphological characteristics of hybrid Venado H74 and its progenitors

In the Table 1 shows the main morphological characteristics of the Venado H74, the simple female cross (M54 x M55) and the male parent CML456 based on the technical guide for varietal description (^{SNICS, 2014}).

Agronomic behavior of the hybrid Venado H74 in localities of High Valleys

The agronomic behavior of the hybrid Venado H74 was evaluated experimentally and in batches of commercial production from 2008 to 2015 in 23 representative localities of environments of deficient, intermediate and favorable weather or with irrigation of aid, with the purpose of studying better the behavior of the global yield and that of the interaction genotype x environment of performance.

At a global level, the yields varied from 2.3 to 12.6 t ha^-1 and represent values of 90 to 126% with respect to the joint yield of commercial controls H-70 and variety creole. The number of days to male flowering ranged between 75 and 108, which correspond to sites located at altitudes of 2 250 and 2 650 meters above sea level, respectively, that is, at higher altitude, the emergence, development of the spike and dispersion of pollen is slower due to lower temperatures of the place. Regarding plant height, Venado H74 showed a plant size that varied from 170 to 230 cm, the highest plant height is usually associated with lower altitude environments and higher available humidity.

The planting that showed Venado H74 ranged between 5 and 10%, which represents minimum to moderate lodging values. The means through localities for yield, male flowering, plant height and planting were 8.2 t ha-1, 96.6 days, 203.5 cm and 7.1%, respectively. Throughout, the Venado H74 test environments were 14.2% higher in performance than the average commercial controls (Table 2). The response of this early hybrid to population densities of 60 to 100 thousand plants ha^-1 was detected in the town of Coatlinchan, State of Mexico with yields of 8.8 to 14.2 under irrigation and 7.1 to 8.9 t ha^-1 in rainy season, respectively (Table 2).

The agronomic management technology for the commercial production of the hybrid Venado H74 is indicated in technical brochure no. 13 for the production of H-70 (^{Arellano et al., 2011}).

Seed productivity of the progenitors of the hybrid Venado H74 in localities of High Valleys

In the Valley of Mexico Experimental Field located in the town of Coatlinchan, Texcoco, State of Mexico at 2 240 meters above sea level, experimental grain yields were recorded for progenitor lines M54, M55 and CML242 of 2.6, 2.5 and 3 t ha^-1, respectively. In terms of yield and seed vigor characters, the lines indicated above were classified as stable when evaluated in three locations of High Valleys and Bajio (^{Hernández, 2018}). Regarding the performance of the female progenitor M55 x M54 established in the field under irrigation at the planting date of May 20 in the town of Coatlinchán (2 230 meters above sea level), State of Mexico, a production of 10 t ha^-1 was recorded (^{Virgen et al, 2009}).

On the other hand, it was found that in plantings with producers from Espiritu Santo-Ixtacuixtla and Francisco Villa, both of Tlaxcala, located at altitudes of 2 430 and 2 530 m, respectively, the simple female cross gave 6.5 and 6.2 t^-1, respectively, with the population density of 83 thousand plants ha^-1 and date of planting on April 19, these yields exceeded 1.5 and 3 t ha^-1 of the female crosses of the commercial hybrids H40 and H50, respectively (^{Virgen et al., 2009}; ^{Virgen et al., 2010}). In the localities of Texoloc, Benito Juárez and San Nicolás Panotla, Tlaxcala at altitudes of 2 225, 2 530 and 2 200 m, respectively, the female progenitor (M54 x M55) yielded 8.6, 6.9 and 6.4 t ha^-1, respectively (^{Virgen et al., 2013}). The yield greater than 3 t ha^-1 of the CML-456 line was obtained in Coatlinchán, State of Mexico and Texoloc, Tlaxcala, reaching 4 t ha^-1 in planting on May 10 in Coatlinchán (^{Virgen et al., 2016}).

The previous results indicate the possibility of obtaining very favorable seed yields from the parents and from the Venado H74 hybrid in localities located between 2 200 and 2 600 meters above sea level, which makes reliable and profitable the multiplication of certified seed of this new corn hybrid in localities of the High Valleys.

The recommended sowing period for certified seed production in the Central Plateu of Mexico is established in April, while the female - male sowing ratio is 6:2, where the male parent should be planted a week before the female, both under the population density of 65 thousand plants per hectare. The beginning of the detasseling period marks the emergence of the spikes, it is recommended to carry out this activity in six days and to consider in the last one, the elimination of the spike (^{Arellano et al., 2011}).

Conclusions

In terms of the productive potential of the regions of the Central Plateau of Mexico and the adaptability of Venado H74, it is established that there are at least 75 thousand hectares in the state of Tlaxcala, 150 thousand in Puebla, 200 thousand in the State of Mexico and 90 in Hidalgo, where the new maize hybrid can participate successfully to increase yields under rainfed or irrigated crops.