In 2016, the H-568 was registered, a hybrid of three lines, that shows great adaptability, and can be planted in the warm areas of the states of Guerrero, Michoacán, Chiapas, Tamaulipas, Morelos, Oaxaca and Puebla. It also complies with the commercial and industrial parameters for the preparation of tortillas by the traditional method, nixtamal-dough-tortilla and due to the characteristics of its grain it can also be channeled to the elaboration of nixtamalized flour. This new maize hybrid has a potential for grain yield of 11 t ha^-1 and in evaluations in different locations of the Low Tropic of México yields fluctuating from 5.6 to 9.5 t ha^-1 were obtained. Currently INIFAP makes it available to maiceros producers of the tropics this new hybrid, as well as its progenitors for the production of certified seed. The ‘H-568’ is a three-line hybrid; it was registered in 2016 before the National Seed Inspection and Certification Service (SNICS), it was assigned with the number 3389-MAZ-1783-1710616/C, its characterization was carried out at the INIFAP’s Iguala Experimental Field in the 2012/2013 and 2013/2014 OI sowing cycles based on the maize technical guide (^{UPOV, 2009}) and on the graphic manual for the varietal description of maize (^{Carballo and Benítez, 2003}). The structure of the hybrid is (T₄₈ x T₄₇) x T₄₉.

T₄₇. Comes from the original T₁₁ line generated in the 50’s in the INIFAP’s Cotaxtla Experimental Field, Veracruz. It was derived from the V-520 C variety, of the Tuxpeño breed collected in San Rafael, Veracruz, in a humid warm climate and its genealogy corresponds to Cap-348-4-1 (^{Martínez, 1988}; ^{Reyes, 1990}). T₁₁ line improving was made by selection per se to a lower plant and cob, using slow inbreeding in order to not lose it in the inbreeding process, since it derived from a completely native maize. The process consisted of alternating an inbreeding cycle by a recombination one, since it was a line of two self-fertilizations (S₂) and with high variability; after four self-fertilizations it was registered as T₄₇, its plant height was 200 cm on average and cob of 110 cm, the male flowering occurs at 58 days and the female occurs one day after.

T₄₈. Comes from the original T₁₂ line generated in the 50’s in the INIFAP’s Cotaxtla Experimental Field, Veracruz. It was derived from the collection made in Tamuín, San Luis Potosí, in a warm dry climate and its genealogy corresponds to SLP-20-34A-2-2-6#-1-3 (^{Martínez, 1988}; ^{Reyes, 1990}). After 10 years of convergent improvement in 2005 several versions of the recovered T₁₂ line were obtained, which were recombined to form a population from which new lines are derived, including the T₁₂ RC₉₃ line that was registered as T₄₈ (^{Gómez et al., 1992}; ^{Gómez, 1994}). Improved T₄₈ line is characterized by low height with 165-180 cm and a 65 to 80 cm cob, it has semierect leaves of plain green color, pods are lime-green, semi-open spike with straight long branches and pink stigmas; the cob is short with 10 to 15 cm of length of good coverage in the bracts, of cylindrical conical shape and with 12 to 14 straight rows; the grain is creamy white and semi-serrated textured. The average male flowering during the summer spring cycle (PV) occurs 57 days after sowing and the day after the female flowering occurs (^{Gómez et al., 2013}).

T₄₇ x T₄₈. The simple cross of these two lines (T₄₇ x T₄₈) generated an intermediate bearing and biological cycle hybrid with an average height of 285 cm and a 140 cm cob, male flowering occurs at 56 days and female at 57 days after sowing, its stigmas are light green-pink; the leaves are slightly curved of lime green color; the spike is compact, with long branches with 7 to 9 lateral branches and green color spikelets; cob is cylindrical with 17 to 20 cm long, with excellent coverage of bracts, having 14 to 16 rows regularly arranged, creamy white grain and serrated texture (^{Gómez et al., 2013}).

T₄₉. It was identified in 2010 as one of the best lines obtained in Iguala from a collection of advanced generations of commercial hybrids whose genealogy is HCF₂-91. It was selected for its very white grain and good size, it is currently actively participating in the new generation of hybrids for the Low Tropic of México.

This line is characterized by being of intermediate cycle, has a low plant and cob size, its male flowering occurs at 59 days and two days later the female, it has stigmas with anthocyanins of intermediate intensity, short cob with 12 to 14 grain rows in straight form, its grains are white and shows a split crown.

“H-568”. The hybrid is intermediate-high size and has a biological cycle of 125 to 130 days, it has a plant height ranging from 270 to 280 cm, tolerant to bending, slightly wavy rectilinear leaves of the laminar margin, medium green color, with male flowering at 58 days and two days later the female flowering; semi-open spike with 13 to 15 primary lateral branches, pink stigmas; cylindrical cob of good bracts coverage, it is 15 to 20 cm length with 14 to 18 straight rows and 31 to 40 grains per row of creamy white color and serrated texture, the appearance of plant and cob are shown in Figure 1. In addition, it shows good characteristics and properties for the production of corn and forage, it meets the commercial and industrial parameters for the preparation of tortillas by the traditional method, nixtamal-dough-tortilla.

Figure 1 H-568 plant and cob appearance. 

This new maize hybrid is very well adapted to the tropical region of the states of Guerrero, Michoacán, Oaxaca, Chiapas, Nayarit, Morelos, Veracruz and Tamaulipas with altitudes lower than 1 000 m, with a precipitation that fluctuates from 800 to 1 000 mm, average annual temperature of 24 to 27 °C and especially to soils of medium to high productivity. This hybrid has been evaluated in different states of the Tropic of México as well as in different countries of Central America, where grain yields from 5.6 to 9.5 t ha¹ have obtained sin owings under rainfed conditions; on the other hand, in the CIMMYT’s MasAgro strategy in its semi-commercial validation of white maize hybrids, carried out in thirty localities of the Mexican Republic during 2012, the H-568 was the best hybrid in grain yield, surpassing the control materials of transnational corporations.

Among the physical characteristics of the ‘H-568’ grain, it can be emphasized that they are of intermediate size (PCG< 33 g), with hectolitric weight of 76.7 kg hL^-1; and hard (IF 33%), characteristics that are in agreement with its percentage of corneal endosperm 42.41%; these values are within reported for tropical maize hybrids in Guerrero (^{Salinas et al., 2010}) and those demanded by the dough-tortilla industrials (IMT) and nixtamalized flour (IHN) (NMX-034), pedicel proportions of 1.55%, pericarp 5.3%, germ 13.3%, floury endosperm 37.4% and corneum endosperm 42.4%, place it within the parameters for commercial toothed maize (^{González, 2009}). Its high proportion of germ, increases the nutritional value of tortillas, since this structure contains protein and triglycerides rich in omega-6 fatty acids (^{Serna et al., 2013}). Higher proportions of oil also improves the texture of tortillas (^{Vázquez et al., 2015}.); however, for the nixtamalized flour industry it would be a limitation, since grains with germ proportions greater than 13% make the nixtamal grinding difficult, since the mills are jammed and cause a rapid deterioration of the flour, because they are quickly fermented.

As for the nixtamalera-tortillera quality, the humidity of its nixtamal is 48.6%, in dough 55.91%, in recently made tortillas is 42.1% and 24 hours after stored at 4 °C is 43%. This indicates that the grains of the ‘H-568’ hybrid are properly dampened with cooking time (45 min) and rest (18 h), reaching humidity similar to hybrids with greater hardness, which contributes to high dough yields, 1.93 kg kg^-1 maize and tortilla of 1.52 kg kg^-1 maize (^{Salinas et al., 2010}). Regarding the grain color and its tortillas, the luminosity in the grains was high 74.73, indicating that these are translucent and bright. In tortillas this value increased especially after two hours of elaboration, changes that are due to the gelatinization of the starches. The reduction of the values in the color in tortillas at 24 h, were minimal and are due to the cooling and retrogradation of the starches. As a result of the characteristics of its grain, the ‘H-568’ hybrid is a good choice for its use and consumption as tortilla, following the traditional dough- tortilla process, as well as channeled to the production of nixtamalized flour.

The seeds production of H-568 hybrid should be performed in a isolated batch following the standards set by the National Service for Inspection and Seed Certification (SNICS) regarding to isolation by distance or time (^{Coutiño, 1993}; ^{Vallejo et al., 2008}); the female:male ratio of 2:1 or 4:2 can be used, sowing the male and female progenitors at the same time. Densities of 60 000 and 70 000 plants ha^-1 are recommended of female and male respectively; thus it occurs on average 5 t ha^-1 of benefit seeds if there is a good agronomic management. INIFAP makes it available to producer organizations and micro-enterprises, the registered seed of the parents to produce the certified seed.