Tropical Grasslands (2009) Volume 43, 139–150 139 Flowering dynamics and seed production of Arachis pintoi and Arachis repens in the Brazilian Cerrados M.A. CARVALHO1, E.A. PIZZARO JUNCAL2 Introduction and J.F.M. VALLS3 1Brazilian Agriculture Research Corporation The genus Arachis is a member of family (Embrapa), Embrapa Cerrados, Planaltina, DF Fabaceae, tribe Aeschynomeneae and subtribe Stylosanthinae. It is endemic in South America - Brazil and, at present, 69 species have been described 2 Pasturas de America, Montevideo, Uruguay (Krapovickas and Gregory 1994). 3Brazilian Agriculture Research Corporation Several species of Arachis have potential to (Embrapa), be incorporated into forage systems, notably Ara- Embrapa Recursos Genéticos e Biotecnologia, chis glabrata (section Rhizomatozae), A. pintoi Parque Estação Biológica, Brasília, DF - Brasil and A. repens (both section Caulorrhizae). These last 2 species, along with A. glabrata, appear as the most promising, since they produce large Abstract amounts of high quality forage and are prolific seeders (Valls and Simpson 1994). A. pintoi and Thirty-two accessions of the Caulorrhizae sec- A. repens (Krapovickas and Gregory 1994) are herbaceous, perennial plants, endemic in Brazil. tion of the genus Arachis were evaluated at 2 dif- They are considered multi-purpose legumes, ferent sites in the Brazilian Cerrados, in terms of being grown for forage, erosion control and orna- flowering period and intensity, seed yield and dis- mental purposes and as ground cover in orchards, tribution in the soil profile. Flowering occurred forests and low-tillage systems. between October and May with the accessions dif- The species of the Caulorrhizae section differ fering in the distribution, intensity and period of widely in terms of seed production. While most flowering. They exhibited a cyclic flowering pat- of the germplasm of A. pintoi can produce high tern, with various peaks of production of flowers. seed yields under natural conditions, A. repens rarely produces any seeds, even though it pro- Differences in maximum flowering intensity were duces abundant blooms (Valls 1992; Pizarro et al. also observed among sites. The average seed 1992; Cook et al. 1994). yield 18 months after planting was 948 kg/ha at Most of the agronomic data already published Location 1 (lowland area) and 327 kg/ha at Loca- on these species was obtained in studies con- tion 2 (well drained area). The accessions exhib- ducted under the coordination of, or with germ- ited great variability for this trait, with an average plasm distributed by, the International Center for broad-sense heritability (H²) value of 0.73. While Tropical Agriculture (CIAT), and represents data exclusively from only the originally collected 99% of the seeds were concentrated in the first accession (GK 12787 or CIAT 17434 or BRA– 6 cm of the soil profile, seeds were recovered to 013251). These results have stimulated the distri- 9 cm depth at Location 1 and to 12 cm at Loca- bution of this accession to several countries, and tion 2. Genetic variability was also observed for resulted in the release of Arachis pintoi selected this trait. from GK 12787 (CIAT 17434 or BRA–013251) in a number of countries, including Australia, Colombia, Costa Rica and Honduras and more Correspondence: M.A. Carvalho, Brazilian Agriculture recently Brazil. Research Corporation (Embrapa), Embrapa Cerrados, BR 020 Km 18, PO Box 08223, Planaltina, DF-Brazil 73310-970. Pizarro et al. (1992; 1993) in Brazil and Argel E-mail: [email protected] and Valério (1993) in Costa Rica demonstrated 140 M.A. Carvalho, E.A. Pizzaro Juncal and J.F.M. Valls great variability in seed yield among accessions 30˝W; elevation 1000 masl). Average annual tem- of A. pintoi, while Ferguson (1994) reported seed perature is 21.9°C, with average annual precip- yields of 7300 kg/ha in Colombia, on highly itation of 1540 mm, mostly occurring during fertile soils. In Australia, Cook and Franklin October – April. (1988) reported seed yields of 1400 kg/ha in cv. Two experiments were established in an Amarillo, 12 months after sowing, while Cook Akuult (low humic gley – Location 1) and in an and Loch (1993) obtained seed yields of 2800 kg/ Ustox (yellow red latosol – Location 2) with 26 ha in a commercial seed crop. accessions of A. pintoi and 6 of A. repens. Phys- The geocarpic characteristic of the genus, with ical and chemical characteristics of the soils are seed-set below the soil surface, makes seed har- presented in Table 1. Supplementary fertiliser vesting difficult and labour-intensive. At har- (44 kg/ha P and 50 kg/ha K) was applied before vesting, 97% of the seeds are not attached to planting. the plant, so the top 10 cm of the soil profile is The experimental design was a randomised revolved and screened on a sieve to collect the block with 2 replications. Plots measured 3.75 seed (Ferguson et al. 1992). m x 4.5 m (16.875 m2), and contained 4 rows The selection of sites with favourable climatic with inter-row spacing of 0.75 m and intra-row conditions, and fine-textured soils with medium spacing of 0.5 m. Plots were established vegeta- to high fertility and high organic matter levels, tively in December 1993. A list of the accessions, could lead to high seed yields. The association identification codes and sites of collection is pre- of the seed fields with other perennial crops, and sented in Table 2. During the first year, the area the development of equipment to mechanise the was mowed every 3 weeks in the rainy season seed-harvesting process, are some of the strate- (Oct – Apr) and every 6 weeks in the dry season gies that will be employed for commercial seed (May – Sep). production of A. pintoi and A. repens. The objective of this research was to evaluate characteristics related to the flowering dynamics Flowering dynamics (period and intensity), seed yield and distribu- tion in the soil profile of 32 accessions of sec- Flowering was observed from October to August. tion Caulorrhizae planted at 2 different sites in However, the data presented in detail in this the Brazilian Cerrados. research relate only to the period December – August, commencing 1 year after planting. Flower counts were taken every week in an Materials and methods area of 0.0625 m² (0.25 m x 0.25 m), randomly chosen in each plot. Numbers of flowers/m² for The work was conducted at the Cerrados the different accessions at both sites were plotted Research Center (CPAC) of the Brazilian Agri- against time to determine their flowering patterns cultural Research Corporation (EMBRAPA), and flowering was related to rainfall and average located in Planaltina, DF (15° 35´ 30˝S, 47° 42́ minimum temperature. Table 1. Physical and chemical characteristics of the low humic gley soil (Location 1) and the yellow red latosol (Location 2). Location Physical characteristics % clay % silt % sand Textural class 1 48 26 26 Clay 2 62 20 18 Clay Chemical characteristics 1 1 2 2 1 3 pH(H2O) Al Ca+Mg P K H+Al OM 1 5.3 0.97 4.34 5.7 77 9.46 0.20 2 4.7 0.56 2.90 1.0 38 6.24 0.18 1 meq/100cc. 2 mg/L. 3 % of organic matter. Flowering dynamics and seed production of Arachis 141 Seed yield Soil samples were taken using a soil core sam- pler (8.9 cm) (Soil moisture Equipment Corpora- Eighteen months after planting, plots were sam- tion, model no 212, Santa Barbara, CA, USA) to pled to assess seed production. Soil samples to a depth of 15 cm, and divided into 5 layers of 3 a depth of 0.25 m from an area of 0.5 m x 0.5 cm each. The soil was screened on a sieve with m were taken. The soil was screened on a sieve a 5 mm mesh to remove the pods, which were with a 5 mm mesh to remove the pods, which then dried at room temperature for 3 weeks and were then dried at room temperature for 3 weeks weighed. Yields of whole fruit (pericarp + seed) and weighed. Calculations were made to deter- per hectare for the different layers were deter- mine yields per hectare. The numbers reported in mined. this research represent the whole fruit (pericarp + seed). Statistical analyses Seed distribution in the soil profile Statistical analyses were performed using the sta- tistical package SAS (SAS Institute Inc. 1985). The 12 accessions with superior agronomic per- Seed yield data were analysed, initially, by loca- formance, in terms of dry matter (data not pre- tion, and then a combined analysis including both sented) and seed yield, were selected to evaluate locations was performed. Duncan’s test was used the seed distribution in the soil profile. At both to test differences between means at P<0.05. locations, 5 samples were taken in each plot, The statistical model used to perform the anal- totalling 10 samples per location. ysis by location was as follows: Table 2. Identification code and site of collection of the A. pintoi and A. repens accessions. Species/ Site of collection1 Lat. (S) Long. (W) Elevation Brazil code (BRA) (State and County) (masl) A. pintoi 013251 BA (Belmonte-Boca do Córrego) 15°52´ 39°08´ 50 015121 GO (Formosa - Faz. Genipapo) 15°26´ 47°21´ 700 015598 DF (Guará - QI 7) 15°49´ 47°58´ 1080 030252 MG (Berilo - Rio Araçuaí) 16°57´ 42°28´ 360 030261 MG (Araçuaí - Faz. Vera Cruz) - - 270 030325 MG (Itacarambi) 15°07´ 44°08´ 510 030333 GO (Formosa - próximo Itiquira) - - - 030368 MG (Unaí - Ribeirão Tamboril) 16°18´ 46°58´ 630 030376 MG (Unaí - Rib.