CG PICAÇO: a new cultivar of sudangrass with high forage performance and seed yield

Abstract

A new cultivar of sudangrass [Sorghum sudanense (Piper) Stapf.] was developed by the method of selection of individual plants with progeny testing. The most important traits are high forage performance, good leaf:stalk ratio, and high seed yield.

Sorghum sudanense (Piper) Stapf.; plant breeding; forage traits

INTRODUCTION

Numerous studies have been carried out to select and genetically improve forage crops, always seeking to associate high yields of dry matter with bromatological quality (Neumann et al. 2011). Therefore, the pressure of natural or artificial selection in species facing animal production aim at obtaining genotypes with emphasis on forage traits, mainly on green and total dry matter and leaf dry matter (Assis et al. 2008). Thus, studies hardly ever aim at a combined selection regarding genetic gain in seed yield (Lopes and Franke 2011).

In Brazil, few forage cultivars are currently commercially available, most derived from apomictic reproduction. Therefore, they are genetically homogeneous and do not generate new variation. This is a threat to national security due to the possible emergence of new pests and most serious diseases (Jank et al. 2011). On the other hand, most tropical forages of agronomic interest have large genetic variability, which can be exploited in the selection of new cultivars with desirable traits (Araújo et al. 2008). Sudangrass [Sorghum sudanense (Piper) Stapf.] is a forage species which has been increasingly used in southern Brazil. It presents annual cycle, and grows in tropical and temperate climates, being tolerant to acidity and low fertility soils, with high biomass yield and optimal recovery after cutting and grazing (Bibi et al. 2010).

The advancement of sudangrass in areas previously occupied by other annual species is a consequence of the high resistance of the species to water deficits, which notoriously occurs during the summer (Pacheco et al. 2013). This culture is widely used for ground cover due to its large biomass, and therefore, it leaves great amount of sudangrass trash on soil. Moreover, its use as forage is relatively new; thus, there are few cultivars registered (MAPA 2014). Its great potential for biomass yield, its tolerance to drought, heat, acid and low fertility soils, its disease resistance, and its ability to compete with weeds (Silva et al. 2014) have been notorious to the production of interspecific hybrids (Sorghum bicolor x Sorghum sudanense), combining the benefits of both species. Zamfir et al. (2001) reinforce that the biomass yield of sudangrass is superior to that of pearl millet and maize, and so is the ability on roots and shoots growth.

In addition, Tomich et al. (2004) did not find differences between the forage potential of sorghum hybrids compared with sudangrass; therefore, they present forage yield similar to a hybrid and with a significantly reduced cost for obtaining seeds.

PEDIGREE AND BREEDING METHODS

The cultivar CG PICAÇO was obtained by the method of selection of individual plants within the "common" original population with subsequent progeny test (VCU tests). In the year 2009, three populations of "common" sudangrass, originated from different edaphoclimatic regions, were sown in the field evidencing great genetic variability within and between populations. Two populations were collected in the fields of Cegil Agro Seeds Company, in São Borja-RS and in Campos de Júlio-MT, and another one was collected by farmers in the municipality of Melo (province of Cerro Largo, Uruguay). The seeds of each population were sown 0.45 m between plants and between lines, on a density of three to four seeds per pit-hole. The established order sought to force competition between plants in the pit-hole, and the one which expressed greater competitive ability in the vegetative stage would remain. There was selection pressure of approximately 3% in 1272 of plants obtained from three populations, based on forage traits and seed yield. In the field, the main trait of analysis was tillering, and it was selected plants which had at least 10 fertile tillers (viable panicles). These plants were cut close to the soil surface at the physiological maturity of seeds, separating the panicles for kiln drying (40 ^oC) until seed moisture reached close to 13%. The rest of the genotype of each plant was weighed in order to assume the potential for biomass yield. Before the cutting, the main panicle of each plant was identified, harvested and packed in paper bags for drying and taken to the laboratory for analysis of traits related to inflorescence components, such as panicle length, panicle mass, number of grains per panicle, mass of grains per panicle, fertility and panicle harvest index. Thus, after analysis of selected genotypes, plants with higher performance for the simultaneous production of forage and seeds were sown in the field, in 2010, in individual plots. In that year, selection occurred between plots, and the selected ones needed to present great uniformity and superior performance. The selected plots were submitted to value of cultivation and use (VCU) test in the following years. The cultivar was called CG 236AR09 in field.

PERFORMANCE

Due to its great potential in biomass and seed yield, in the years 2011 and 2012, CG 236AR09 line was tested in VCU tests, which were carried out at three different locations: Augusto Pestana (lat 28º 28' 51'' S, long 53º 58' 07'' W, alt 385m asl) and São Borja (lat 28º 54' 40'' S, long 55º 29' 06'' W, alt 137m asl), in Rio Grande do Sul, and São José do Cedro (lat 26º 27' 46'' S, long 53º 32' 53'' W, alt 627m asl), in Santa Catarina. Tests were carried out in a randomized block design with four replications. Each experimental unit, which included a genotype to be tested, consisted of 5 rows of 5 m of length, spaced 0.20 m apart, in order to compose a plot of 5 m². Seeding rate was 25 kg of seeds ha^-1 for cultivars of sudangrass and pearl millet, and 12 kg seed ha^-1 for sorghum cultivars. The evaluated traits was the total yield of fresh matter (TFM) by cutting 1 m² of each plot of which plants reached 60 - 65 cm height, leaving a residue of 10 cm above the soil. Samples of each genotype were weighed to obtain the TFM, and then, 100 grams were separated for performing botanical separation. Therefore, it was analyzed the fresh matter of leaves (FML) and fresh matter of stalks (FMS), and after, they were converted to kg ha^-1. Subsequently, samples were placed to dry in an oven with forced ventilation at 65 °C until constant weight to be analyzed again, obtaining estimates of total dry matter (TDM), dry matter of leaves (DML), and dry matter of stalks (DMS).

For analysis of seed yield, another experiment was carried out in order to obtain greater reliability of selection applied on components of seed yield of the cultivars. Thus, the experiment was carried out in randomized block design with three replications. Each experimental unit, which included a genotype to be tested, consisted of 5 rows of 5 m length, spaced 0.20 m apart to compose a plot of 5 m². The seeding rate was 25 kg seed ha^-1 for cultivars of sudangrass and pearl millet, and 12 kg seed ha^-1 for sorghum cultivars. To estimate the yield of seeds, it was carried out harvesting of the three central rows of each plot, comprising an area of 3 m², as soon as seeds reached the stage of physiological maturity. Panicles were weighed and threshed with estimated values in kg ha^-1. For not having available seeds of this cultivar (IPA Sudan 4202) registered at MAPA when the study was carried out, it was used as control, in both experiments, one pearl millet cultivar (ADR 500 - "SuperMassa"), two forage sorghum hybrid cultivars (AG2501C and JUMBO) and the sudangrass "common" population. In these same year in Augusto Pestana, the experiment was carried out with the purpose of doing the DHS tests (Differentiation, Homogeneity and Stability), comparing with the same cultivars control.

Table 1 presents the forage yield and seed yield of CG PICAÇO cultivar compared to controls. In 2011, in all environments evaluated, the new cultivar of sudangrass was superior to all the controls, including sorghum hybrid, for all forage traits analyzed, providing greater supply of total dry matter and leaf per hectare. However, for the seed yield, hybrids were more productive. Moreover, the CG PICAÇO cultivar showed higher yield performance compared to "common" sudangrass, indicating the highest genetic gain from selection process.

Table 1.
Performance of forage cultivars value for cultivation and use assay, carried out in 2011, in three different soil and climatic regions

• * TFM= Total Fresh Matter; FML= Fresh Matter of Leaves; FMS= Fresh Matter of Stalks; TDM= Total Dry Matter; DML= Dry Matter of Leaves; DMS= Dry Matter of Stalks; SY= Seed Yield.

In the second year of evaluation of VCU test (2012), due to the favorable year of production, all genotypes had higher performance than the previous year. This fact did not change the behavior of genotypes since the cultivar CG PICAÇO had forage performance superior to the other controls at all locations evaluated, and hybrids of sorghum obtained higher seed yield mean (Table 2).

Table 2.
Performance of forage cultivars value for cultivation and use assay, carried out in 2012 in three different soil and climatic regions

• * TFM= Total Fresh Matter; FML= Fresh Matter of Leaves; FMS= Fresh Matter of Stalks; TDM= Total Dry Matter; DML= Dry Matter of Leaves; DMS= Dry Matter of Stalks; SY= Seed Yield.

Table 3 presents the mean for each genotype in both years of evaluation for different environments. Thus, again, the cultivar CG PICAÇO was superior to the control cultivars at the three locations. In this sense, the environment Augusto Pestana was the most favorable for cultivars performance; however, the environment of São Borja was the most restrictive. In the overall analysis, gathering the means of years and locations, the best control was the hybrid cultivar of forage sorghum, called JUMBO, with mean yield of 74089 and 14602 kg of fresh and dry matter per hectare, respectively. On the other hand, the cultivar CG PICAÇO obtained yields of 92726 and 18486 kg of fresh and dry matter ha^-1, respectively, exceeding by 25 and 27% the control. However, despite producing greater amount of leaf ha^-1 and greater amount of dry matter ha^-1, CG PICAÇO presents lower leaf:stalk ratio (0.93:1) than sorghum AG2501C (0.95:1) and JUMBO (1,10:1), but much higher than the "common" sudan (0.77:1) and pearl millet ADR 500 (0.82:1). It is noteworthy that leaf:stalk ratio obtained for each cultivar is derived from values of MDL divided by the MDS overall analysis (Table 3). In relation to seed yield, the highest yield was obtained by AG2501C hybrid, with 3268 kg ha^-1, followed by JUMBO (3145 kg ha^-1) and CG PICAÇO (2955 kg ha^-1). When comparing cultivar CG PICAÇO with the "common" sudan, it is evident the great genetic gain from selection process, reaching 55% more seed yield, from 1907 to 2955 kg ha^-1. Moreover, it increased yield in 37 and 47% more on fresh and dry matter, and established better leaf:stalk ratio. It is important to note that, although the two years of evaluation are different, as well as the evaluation site, the cultivar CG PICAÇO showed better performance in forage traits in all environments, revealing an important technology product to be available to Brazilian farmers, especially to those that produce milk and meat on pasture.

Table 3.
Mean performance of cultivars of forage value for cultivation and use assay, carried out in the years of 2011 and 2012, in three different soil and climatic regions

• * TFM= Total Fresh Matter; FML= Fresh Matter of Leaves; FMS= Fresh Matter of Stalks; TDM= Total Dry Matter; DML= Dry Matter of Leaves; DMS= Dry Matter of Stalks; SY= Seed Yield.

SEED MAINTENANCE AND DISTRIBUTION

CG PICAÇO is registered in the Ministry of Agriculture, Livestock and Food Supply, number 32394 (MAPA 2014). Cegil Agro Seeds (Celso L. Arenhardt & Cia Ltda.) is responsible for maintaining the cultivar genetics and basic seeds. Seeds are sold to producers accredited by the company.

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Publication Dates

• Publication in this collection
  Mar 2015

History

• Received
  24 May 2014
• Accepted
  17 Aug 2014