ABSTRACT. Considering the expected genetic variability of elephant grass (Pennisetum purpureum), due to its cultivation in different continents, we characterized and estimated the genetic divergences between 46 accessions of elephant grass with different edaphoclimatic adaptations, using RAPD and ISSR markers. We evaluated, comparatively, the consistency of the information achieved with these markers. Twenty-six RAPD and 25 ISSR primers were employed. The RAPD markers produced 185 bands, 72% of which were polymorphic, with a mean of 5.11 polymorphic bands per primer. The 25 ISSR starters produced 216 bands; 76% were polymorphic, with a mean of 6.56 polymorphic bands per primer. The correlation between the genetic distances achieved by the RAPD and ISSR markers was 0.76, which is highly significant by the Mantel test. Based on UPGMA grouping, considering the point of sudden change, five and six groups were formed for the data from the RAPD and ISSR markers, respectively. Genetic diversity in elephant grass These markers provided partially concordant groups, indicating that these techniques can provide consistent information and consequently could be used in studies of genetic diversity among accessions.

At the International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia, 171 germplasm accessions of Napier grass were studied using 20 SSR markers with the objective of assessing the allelic richness and genetic diversity of the collections held at ILRI and the Brazilian Agricultural Research Corporation (EMBRAPA), and to determine distinct accessions to be introduced to enhance the diversity in each of the genebank collections. A total of 148 alleles were observed in the whole collection, of which 140 and 93 alleles were observed in the ILRI and EMBRAPA collections, respectively. Fifty-five and 8 alleles were found to be unique to the ILRI and EMBRAPA collections, respectively, while 85 alleles were shared between the collections. The number of alleles per marker ranged from 1 to 23 with an average value of 7.4 across both collections. The heterozygosity per locus ranged from 0.000 to 0.808 with an average value of 0.463. A principal coordinate analysis grouped accessions into 3 main groups, whereas a hierarchical cluster analysis indicated 4 main clusters. From a genebank management and conservation perspective, the marker profile of the accessions was used in the process of selecting and acquiring distinct lines to be added to the ILRI and EMBRAPA collections. Accordingly, 54 accessions and elite lines were selected and introduced from EMBRAPA to the ILRI collection, while 8 distinct accessions from ILRI were added to the EMBRAPA collection. In general, a useful marker profile of an expanded Napier grass collection has been generated which could be used to enhance the conservation, use and management of the available genetic resources of this important forage crop.

A study was carried out to evaluate the development of 12 tetraploid alfalfa cultivars exposed to Al toxicity in nutrient solution. Newly germinated seedlings of cultivars Alfa 200, Alto, Araucana, Costera, Crioula, Esmeralda, Falcon, F-708, Rio, Romagnola, Valley Plus, and Victoria, were exposed to either 0, 4, 8 or 12 mg·L^-1 Al³⁺. Plants were analyzed regarding root length (RL) and dry matter (RDM), aerial part length (APL), and dry matter (APDM), hypocotyl length (HypL) and dry matter (HypDM), epicotyl length (EpiL) and dry matter (EpiDM), and petiole length (PetL), and dry matter (PetDM). Results indicated that, although all genotypes exhibited detectable sensitivity to such a stress, cvs. Crioula, Victoria and Alpha-200 were tolerant to 4 mg·L^-1 Al³⁺ toxicity. It was also concluded that Al³⁺ levels up to the 4 mg·L^-1 will be effective for screening tetraploid alfalfa genotypes regarding this type of stress, when evaluations are made in nutrient solution. Finally, RL is the most suitable variable for conducting such evaluations, but all variables related to dry matter in the aerial part are also recommended

-The objective of this work was to evaluate the potential of allohexaploid pearl millet x elephantgrass (HGL) population for a recurrent selection program through open-pollinated progenies. Seventy-eight progenies, one representative sample of the population, and two commercial cultivars, Pioneiro and Paraíso, were evaluated in a 9x9 triple lattice design, in two sites. Plant height and dry matter yield were evaluated in three and four cuts, respectively. For plant height, the 17 best progenies were similar to both commercial controls, while for dry matter yield they were higher than 'Paraíso' and lower than 'Pioneiro'. The correlation between progenies and cuts indicated that the fourth cut represents the mean of all cuts, and the possibility of using early selection. Heritability estimates considering cuts and sites were 56.9% for plant height and 58.8% for dry matter yield, and the expected response to selection was 23.4% for dry matter yield and 18.1% for plant height. These results demonstrate the promising HGL population potential for a recurrent selection program.Index terms: Pennisetum, heritability, response to selection, split-plot lattice design. Potencial da população alohexaplóide de milheto x capim-elefante para um programa de seleção recorrenteResumo -O objetivo deste trabalho foi avaliar o potencial para programa de seleção recorrente, em uma população alohexaplóide de milheto x capim-elefante (HGL), por meio de progênies de polinização aberta. Setenta e oito progênies, uma testemunha representativa da população e duas cultivares comerciais, a Pioneiro e a Paraíso, foram avaliadas no delineamento látice triplo 9x9, em dois locais. Os caracteres altura de plantas e produtividade de matéria seca foram avaliados por três e quatro cortes, respectivamente. Quanto à altura de plantas, a média das 17 melhores progênies foi similar às das testemunhas comerciais e, quanto à produtividade de matéria seca, foi maior do que a da 'Paraíso' e menor do que a da 'Pioneiro'. A correlação entre progênies e colheitas mostrou que a quarta colheita representa a média de todas as colheitas e a possibilidade de seleção precoce. As estimativas de herdabilidade na média das colheitas e locais foram de 56,9% para altura de plantas e de 58,8% para produtividade de matéria seca, e a reposta esperada com a seleção foi de 23,4% para produtividade de matéria seca e 18,1% para altura de plantas. Esses resultados demonstram o potencial promissor da população HGL para programa de seleção recorrente.Termos para indexação: Pennisetum, herdabilidade, resposta à seleção, látice de parcelas subdividas.

ABSTRACT. Interspecific hybridization between Napier grass (Pennisetum purpureum), which is widely grown in Brazil for cattle forage, and pearl millet (Pennisetum glaucum) has been used as a breeding strategy for the development of improved cultivars. However, the hybrid between these two species is sterile due to its triploid condition (2n = 3x = 21 chromosomes), which hinders its use in crop breeding programs. It is known that genomic alterations result from the hybridization process. In order to measure the loss of DNA during embryo development, we used flow cytometry to estimate the nuclear DNA content of triploid and tetraploid embryos produced by interspecific hybridization between Napier grass and pearl millet. The triploid and tetraploid hybrids had a mean DNA content of 4.99-4.87 and 5.25-4.84 pg, at 10 and 30 days after pollination, respectively. The mean reduction in DNA content was higher in the tetraploid hybrids. The flow cytometry results revealed progressive genomic instability in these triploid and tetraploid hybrids, with this instability causing significant alterations in the DNA content of the hybrids.

The interference imposed by weeds is one of the most important factors limiting elephant grass forage yield. Two experiments were carried out in 2015/2016 and 2017 to evaluate the selectivity and weed control of 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides applied alone or in combination with atrazine in elephant grass. The treatments applied in the experiment conducted in Valença, Rio de Janeiro State, Brazil, were as follows: two rates of mesotrione (0.072 and 0.144 kg ha -1 + 0.5% v/v mineral oil -Assist®), two rates of tembotrione (0.075 and 0.100 kg ha -1 + 0.5% v/v mineral oil -Aureo®), atrazine + mesotrione (1.25 + 0.072 kg ha -1 + 0.5% v/v mineral oil -Assist®), atrazine + tembotrione (1.25 + 0.100 kg ha -1 + 0.5% v/v mineral oil -Aureo®), atrazine + mesotrione (1.25 + 0.072 kg ha -1 ), atrazine + tembotrione (1.25 + 0.100 kg ha -1 ) and two checks (weed-free check and weedy check). The same herbicide treatments and a check without application were applied in an experiment conducted in Coronel Pacheco, Minas Gerais State, Brazil. Two application rates of mesotrione with the addition of mineral oil or the tank mixture of atrazine plus mesotrione, with or without the addition of mineral oil, did not provide injuries capable to reduce elephant grass forage yield. Tembotrione was phytotoxic to elephant grass when applied with mineral oil. Atrazine plus tembotrione in a tank-mix, with or without mineral oil, were also phytotoxic to elephant grass. All treatments provided satisfactory weed control.

Elephant grass is a tropical forage crop highly used in dairy cattle production, in Brazil. It has been getting special attention, because of its bioenergy potential, medicinal properties, and bioremediation profile. The aim of the present study is to investigate the effects of thermotherapy based on clonal cleaning methods and meristem culture on the mineral content of elephant grass (Cenchrus purpureus (Schumach.) Morrone). Cultivars “Mineiro”, “Taiwan A-147” and “Pioneiro” were subjected to the following methods: thermotherapy (T) combined to meristem culture (MC), meristem culture and mature stems (control). The experiment assessed the mineral contents of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) at three cuttings, which were performed every 60 days, for 180 days. There was lack of effects from these methods on the mineral content of approximately 66% of the carried out assessments, standing out unanimity for all cultivars, methods, and most of the cuts. T+MC was the only method showing positive effect on P and Ca content, in all cuts, in the cultivars Taiwan A-147 and Pioneiro, respectively. There was clear negative effect of cleaning methods on P and Ca content, in all cuts, for cultivar Mineiro, and on Mg, for cultivar Taiwan A-147. These results, along with the positive effects observed in vegetative and nutritional parameters shown in other articles published in this Journal, show that the clonal cleaning methods are strongly recommended for cultivars with more than 15 years of ripe stem propagation.

Elephant grass plays important role in dairy cattle production and has received special attention due to its potential in bioenergy and phytoremediation, as well as to its medicinal properties. The aim was investigating the effects of thermotherapy and meristem culture on elephant grass (Cenchrus purpureus (Schumach.) Morrone) forage production and nutritional value. Cultivars “Mineiro”, “Taiwan A-147” and “Pioneiro” were subjected to the methods: thermotherapy plus meristem culture, meristem culture and mature stems (control). The experiment assessed the tiller number (TN), tiller height (TH), number of leaves/tiller (NLT), leaf/stem ratio (LSR), crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF), at three cuts performed every 60 days for 180 days. It was observed beneficial influence on the evaluated traits, which indicated how cleaning methods work. Cultivar “Mineiro”, with more than 20 years of use, was more sensitive to the cleaning methods showing than cultivars “Taiwan A-147” (15 years of use) and “Pioneiro” (less than 10 years). It was observed that methods have affected the NT, TH, SDM, LSR, LDM, CP, and NDF. And, that the cultivars genotype effect in a different way the NT, TH, NLT, SDM, LSR, and CP. Overall, Cleaning methods produced an increase in the evaluated parameters over 100% for the cultivars Mineiro and Taiwan when compared with the traditional method and presented low or negative effect for Pioneiro cultivar This evidenced that the traditional propagation method affects forage production and quality over generations in vegetative propagated species. Basic biotechnology techniques such as meristem culture associated or not with thermotherapy can restore the productive potential being recommended for old asexually propagated cultivars with more than fifteen years of cultivation.