The oldest remains (8 700 years AP) of maize were found in the Iguala Valley, Guerrero, specifically in the shelter of Xihuatoxtla in the community of Tlaxmalac where explorations were made, because everything indicated that in the Balsas Basin is located the greatest diversity of Teocintle, Zea mayss ppparviglumis populations, recognized as the direct ancestor of maize (^{Hastorf, 2009}) and tripsacum, the other recognized ancestor of maize. In addition, 22 native maize races have been detected in the state, placing it as part of the center of origin and genetic diversity center (^{Hernández and Alanis, 1970}; ^{Sánchez et al., 2000}).

In regions of intermediate altitude (1 200 to 1 700 m) it is feasible to sow native materials with some level of improvement, mainly in valleys and lands with small hills; while on high hills grounds and thin soils and the best choice is still the use of native populations (^{Gómez et al.,1988}). In 1985, the Maize Genetic Improvement Program of INIFAP-Guerrero began the process of obtaining new materials that included native germplasm. Among other activities, native maize were combined with improved maize of wide adaptation, generating a series of varietal hybrids with greater genetic potential, better agronomic characteristics and with very good adaptation to medium potential environments of the semi-warm region.

Specifically, this research began with the evaluation of the improved native populations of subtropical origin sown in Iguala that were crossed with improved tropical populations in the adaptation process to Valles Altos for a period of ten years. For this purpose two groups of varieties were formed, the first one was composed of three improved native varieties adapted to the mountains of Guerrero that were used as masculine progenitors, the subtropical interracial complex (CIST), formed with germplasm of the Pepitilla, Tuxpeño, Celaya and Conic races in which recurrent half-sibling selection was applied during three selection cycles; VE-1, obtained from the crossing of V-531 with a semi-wide native maize; VE-3, obtained from the crossing of a drought resistant tropical experimental variety (a population integrated with Tuxpeño, ETO, Cristalino del Caribe and Costa Tropical germplasm) with a semi-broad maize from Quechultenango municipality, Guerrero, backcrossed to the native.

The second group was composed of four tropical varieties submitted for 10 years to a selection process for adaptation to Valles Altos (2 250 m altitude) that were used as female progenitors in the crossings; VS-521, synthetic variety obtained by selection of V compound, composed by 20 families of complete siblings (FHC) of the Costeño Estabilizado III of collections from Llera, Tamaulipas; VS-529, formed by the recombination of seven lines derived from the VS-521 and seven varieties of VS-524; SINT-3-HE, integrated experimental synthetic variety of eight erect leaf lines derived from B670 hybrid; HE-1, a female progenitor experimental hybrid of the H-516 hybrid, which led to advanced generations of recombination for its genetic stabilization.

With these seven populations, 12 intervarietal crosses (CI) were generated under a 3*4 factorial genetic design, which, together with its progenitors and controls, were evaluated in 16 intermediate altitude environments during the summer-autumn 2004 to 2008 cycles aiming to identify some CI of commercial value. With the information generated from these evaluations, the VS-529*VE-1 was identified as the best inter-varietal cross that gave rise to the new ‘HV-240’ maize genotype, which shows better agronomic characteristics than the native populations currently planted in the low mountain of Guerrero, it was registered in 2016 before the National Seed Inspection and Certification Service (SNICS), assigned with the number 3390-MAZ-1784-1710616/C, its characterization was carried out in the INIFAP’s Iguala Experimental Field (^{UPOV, 2009}) and in the graphic manual for the varietal description of maize (^{Carballo and Benítez, 2003}).

The commercial hybrid ‘HV-240’ with biological cycle of 125 days, has a plant height that varies from 250 to 270 cm, is tolerant to bending, has slightly curved leaves of medium green color, with male and female flowering at 64 days; compact spike with 13 to 15 primary lateral branches, light green stigmas; cylindrical cone cob with a good coverage of the bracts, is 15 to 20 cm long with 12 to 14 straight rows and 51 grains per row, its grain is creamy white with semi-toothed texture; the appereance of plant and cob are shown in Figure 1. In addition, it shows good characteristics and properties for the production of corn and forage, and it complies with the commercial and industrial parameters for the preparation of tortillas by the traditional, nixtamal-dough- tortilla method.

Figure 1 Appereance of plant and cob of the ‘HV-240’. 

Regarding to grain quality, the HV-240 intervarietal hybrid has white grains, intermediate size of 35.2 g, with a hectoliter weight of 74.9 kg hL^-1, a value that was slightly higher than that established by the NMX-034 (Part 1) for maize destined to the nixtamalization process. Its endosperm has hard texture (IF= 21% of floating). The dissection approval showed that with the exception of pedicel percentage (1.9%), the rest of the components are in the range accepted by the nixtamalized flour industry. The solubilized solids in the nejayote were on average 4.72%, while the nixtamal retained pericarp amounts from 39 to 51% (x= 44.3%), reaching an average humidity of 46.8%. The dough recorded an average moisture of 59.9%, associated with a dough yield of 2.1 kg kg^-1 maize.

The average yields of tortillas were 1.44 and 1.4 kg per kg of maize, which is good. The moisture of the tortillas at 2 (x= 42.2%) and 24 (x= 42.5%) hours after elaboration, were very similar between them. In the strength required for breaking tortillas (FZA), it is shown that two hours after processing, they required 310.5 gf and had a longer elongation (8.7 mm), 24 h after being packed in polyethylene bags and stored at 4 °C in the refrigerator, the force required was increased minimally (12.6%), and it was at 48 h where the hardness increased by 28%. The storage time increased the hardness of the tortillas and reduced the elongation or elasticity of the HV-240 tortillas. The tortillas, did not undergo color changes due to storage, an attribute that is demanded by the tortillas producing industries.

The ‘HV-240’ maize is very well adapted to the semi-warm areas of the states of Guerrero, Morelos, Oaxaca and Puebla, with altitudes from 1 200 to 1 700 m, precipitation from 850 to more than 1 000 mm, average annual temperature from 22 to 25 °C; is well adapted to soils of not so pronounced slopes and pH from 7.5 to 8.3. The results obtained in the different evaluations carried out in the period from 2011 to 2015 in more than 20 environments of Guerrero, the ‘HV-240’ exceeded the native corn with 15% of grain yield, corresponding from 600 to 800 kg ha^-1. On the other hand, in the work performed in the spring-summer cycle from 2005 to 2009 on stability, combinatorial ability, heterosis and agronomic behavior of the best intervarietal crosses, information that allowed the commercial liberation of the VS -529*VE-1 (HV-240) varietal hybrid was generated (^{Palemón et al., 2011}; ²⁰¹²).