1 Crop Breeding and Applied Biotechnology - 20(3): e309320310, 2020 UENF MSV2210 and UENF MS2208: Silage and green maize hybrids for Rio de Janeiro State, Brazil

: This study described the main characteristics of the maize cultivars UENF MSV2210 and UENF MS2208. Adapted to the North and Northwestern regions of the state of Rio de Janeiro, they have a high agronomic performance and were developed for both silage and green maize production.


INTRODUCTION
Maize (Zea mays L.) is a cereal cultivated in almost all agricultural regions of the world and is economically and socially extremely important.It is used in food, feed and fuel production as well as for industrial purposes (Sindmilho and Soja 2005).Worldwide, the USA is the largest maize producer, followed by China and Brazil, with an estimated output of 371.0, 259.1 and 68.5 million tons, respectively (FIESP 2018).According to estimates, the area of maize cultivation in the 2018/2019 growing seasons in Brazil was 17.242 thousand hectares, producing an estimated yield of 5.524 kg ha -1 , corresponding to an output of 95.254 thousand tons (CONAB 2019).
According to the Agricultural Census of 2017 in Brazil, around 5 million tons of green maize were produced in that year.The Southeast and Central-West regions accounted for about 3 and 94% of this total production, respectively (IBGE 2018).In the Southeast region, Rio de Janeiro is the state with the lowest number of agricultural production units.Of the 57 vegetables listed by IBGE (2018), green maize is the 15 th most produced.According to preliminary data of fodder maize of the Agricultural Census of Brazil in 2018, the largest growing regions (Southeast, South and Central-West) produced 210.535.393 million tons of silage maize (IBGE 2020).
Among the forages, maize is one of the most commonly used in animal feed.Around 70 to 80% of the production is used in animal diets, destined for animal protein production in, e.g., eggs, meat and milk (Alves et al. 2015).According MG Pereira et al. to Paziani et al. (2009), maize is the most commonly used crop for silage production because of its high nutritional value associated with high yields.However, to meet the standards, maize cultivars adapted to different environmental conditions must be used.
A major share of the current yield potential of this crop in Brazil is the result of significant advances in breeding programs.Over the years, these have progressively improved agronomic characteristics related to grain yield, disease resistance and adaptability to adverse conditions in the country (Pereira et al. 2019).In the North and Northwest of Rio de Janeiro, maize is an alternative income source for small and medium producers.The application of new scientific technologies to develop improved cultivars adapted to the climate conditions of the North and Northwestern state of Rio de Janeiro would provide an additional relevant increase in roughage production during the annual dry periods, aside from boosting the regional economy by the commercialization of green maize.
Not only in view of both the attractive growth prospects for silage maize on the market and of the complete dependence of Brazilian livestock on this additional forage source, but also because no Brazilian breeding programs have so far focused on forage species, nor are there any specific varieties available to meet the demand, this regionspecific research was urgently needed.
The Value for Cultivation and Use (VCU) tests are essential for the registration of new cultivars developed by plant breeding programs.Once registered by the Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA 2019a), the cultivar is available in the register of the National Register of Cultivars (RNC) and can thus be distributed to farmers.To foster the cultivation of silage and green maize in the North and Northwest of Rio de Janeiro, the State University of Northern Rio de Janeiro has been developing research in the area of maize breeding, with a view to the registration and release of region-specific cultivars with high agronomic potential.

BREEDING METHOD
Eight genotypes of the maize collection of the State University of Northern Rio de Janeiro were selected (UENF-2205, UENF-2198, UENF-2207, UENF-2208, UENF-2209, UENF-2210, UENF-2202, UENF-2191), all of the heterotic group "dent", from which the topcross hybrids were derived.Each genotype was crossed with a single tester, Piranão 12.The topcross hybrids were developed on an isolated field of the Experimental Station of Ilha Barra do Pomba-RJ.The topcross hybrids were selected based on the fresh matter yield, after four years of testing (Crevelari et al. 2017, Crevelari et al. 2018).
Of each genotype, five seeds per meter were planted in one 20.0-mrow (plant spacing 0.20 m, row spacing 1.0 m), with a total of 100 plants per row.During flowering, the plants used as female parents were detasseled before the ears released the style/stigma, to avoid undesirable crosses.In this way, the style/stigma received pollen only from the tester.Harvest was performed 120 days after sowing.The Value for Cultivation and Use (VCU) of the hybrids was tested during the main and second growing seasons, simultaneously at three locations: Antônio Sarlo State College of Agriculture, Campos dos Goytacazes, -RJ; Campus Cambuci of the Federal Institute of northern Rio de Janeiro (IFF-RJ) and at the Experimental Station of Ilha Barra do Pomba in Itaocara -RJ, in 2017/2018 and 2018/2018, i.e., in a total of six environments.
The experiment was arranged in a randomized complete block design with three replications, with 11 treatments each, eight topcross hybrids (UENF-2205, UENF-2198, UENF-2207, UENF-2208, UENF-2209, UENF-2210, UENF-2202 and UENF-2191) and three controls (AG 1051, BM 3061 and UENF 506-11).The experimental units consisted of one 8.0-m row (plant spacing 0.20 m, row spacing 1.0 m), resulting in a stand of 40 plants per plot.Cultural treatments were applied as recommended for the crop (Fancelli and Dourado Neto 2000).The plants were harvested by cutting at 20 cm above the ground, when the grains were in growth stage R4, called dough stage (3/4 milkline) for silage maize.At the milky grain growth stage (R2), another harvest was performed to determine ear yield without straw (EYWS) The characteristics were evaluated based on the Minimum Requirements for the determination of VCU of maize (Zea mays), for the inclusion in the National Register of Cultivars (MAPA 2019b).Combined analysis of variance and Tukey's mean test were performed with software Genes (Cruz 2013).

PERFORMANCE
Significant effects (p < 0.01) for all studied characteristics were observed, which indicated genetic variability between cultivars (Table 1).The experimental precision was concluded to be within normality and the variation coefficient varied from 8.63%, in fresh matter yield (FMY), to 11.54%, in ear yield without straw (EYWS).Meanbased heritability ranged from 94.04% FMY to 94.56% EYWS (Table 1).
The overall EYWS mean of cultivars UENF MSV2210 and UENF MS2208 was superior or equivalent to that of the controls UENF 506-11 and AG 1051 (Table 2).For this characteristic, the coefficient of experimental variation ranged from 8.96 to 13.22% between environments and periods, indicating high experimental accuracy (Table 2).
Interestingly, the overall FMY mean of the cultivars UENF MSV2210 and UENF MS2208 exceeded that of the commercial controls (Table 2).The experimental coefficient of variation ranged from 6.44 to 11.34%, indicating a high experimental precision for the evaluated trait (Table 2).
The agronomic performance of the cultivars UENF MSV2210 and UENF MS2208 was very good in most environments and evaluation periods, making them recommendable for silage and green maize production in the North/Northwestern region of Rio de Janeiro state.MG Pereira et al.

OTHER TRAITS
Additional characteristics were assessed based on a cultivar inscription form for registration by the National Cultivar Register of the Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA 2019b).
The morphological characteristics were assessed at different phenological stages, based on the standard maize descriptors.Those of the two cultivars UENF MSV2210 and UENF MS2208 were generally similar, most likely due to the parent in common.
Both cultivars have the following descriptive characteristics: pointed first leaf tip shape; small angle between leaf blade and stem, measured immediately above the upper ear; straight shape of leaf blade above the upper ear; medium tassel length of the main stem, measured as the distance from the point of origin to the tip of the main stem; medium angle between the main tassel stem and lateral branch, in the lower third of the tassel; absent anthocyanin staining of the stigma and dent grain type, measured in the middle third of the ear.
The cultivars UENF MSV2210 and UENF MS2208 have a super early to early cycle, with male and female flowering between 58 and 64 days after sowing.The plant height is medium to high (2.79 -2.96 m) and ear height (1.74 -1.97 m).This is however not a problem, since the lodging risks until harvest time are lower for green and silage than for dry grain maize.For mean ear length and diameter, respective variations of 18.80 -19.04 cm and 43.38 -47.14 mm were recorded for UENF MS 2208 and UENF MSV2210 (Table 3).Grain texture and color and husk coverage degree of the evaluated cultivars were classified as dent, medium yellow and tight, respectively (Table 3).
In terms of the main maize diseases, the cultivars UENF MSV2210 and UENF MS2208 were moderately resistant to Helminthosporium leaf spot and Southern corn rust.Two evaluations were carried out within a fortnight, assessing from flowering until the point called dough stage, based on the Agroceres (1996) evaluation scale.

SEED PRODUCTION AND DISTRIBUTION
The cultivars UENF MSV2210 and UENF MS2208 were registered by the Ministry of Agriculture, Livestock and Food Supply -MAPA on November 12, 2019, under number 41721 and 41705 respectively.The State University of Northern Rio de Janeiro, together with the seed company Rio Norte Sementes based in Campos dos Goytacazes -RJ, are responsible for the production and trade of hybrid seeds.

Table 1 .
Summary of the combined analysis of variance applied to two traits assessed in maize cultivars in three counties of the North and Northwest of Rio de Janeiro state, in the growing seasons 2017/2018 and 2018/2018

Table 2 .
Performance of the maize cultivars UENF MSV2210, UENF MS2208 and controls AG 1051 and UENF 506-11 at three locations of the North and Northwestern state of Rio de Janeiro, in the 2017/2018 and 2018/2018 growing seasons Means followed by the same letter in the same row do not differ statistically from each other by Tukey's test (p≤0.05).* Tukey's test was performed based on the 11 treatments evaluated in tests of the value for cultivation and use (VCU).

Table 3 .
Means of agronomic characteristics of the maize cultivars UENF MSV2210, UENF MS2208, and controls AG 1051 and UENF 506-11 in Value for Cultivation and Use (VCU) tests in three counties of the North and Northwestern state of Rio de Janeiro, in the 2017/2018 and 2018/2018 growing seasons