Fredolino G. Santos

Reaction of sorghum genotypes to the anthracnose fungus Colletotrichum graminicola

The reactions of 22 sorghum (Sorghum bicolor) genotypes to six previously identified races of the sorghum anthracnose fungus Colletotrichum graminicola, were evaluated under greenhouse and field conditions. Races were inoculated in separate tests in the greenhouse. In the field, spreader rows of a susceptible genotype were artificially inoculated with a mixture of the six races of the pathogen. In the greenhouse tests, nine genotypes showed resistance to all six races. In the field high levels of dilatory resistance was observed in the sorghum genotypes CMSXS169 and CMSXS373.

Differences in competitive ability among races of Colletotrichum graminicola in mixtures

Mixtures of races of Colletotrichum graminicola, causing sorghum (Sorghum bicolor) anthracnose and differing in their virulence range, were inoculated for five and six generations on the susceptible sorghum cultivar BR009 (Tx623), in two experiments in a greenhouse. In each generation a sample of 50 single spore isolates was obtained and inoculated on a standard differential set to determine the proportion of each race in the mixture. Isolates of the race 30A, with the narrowest virulence range, predominated over isolates of the more complex races 31B, 31C and 31E indicating the existence of differences in the survival ability among races of this pathogen.

Diversidade populacional de Colletotrichum sublineolum em seis localidades no Brasil

Foi objetivo deste trabalho caracterizar a populacao de Colletotrichum sublineolum Henn. por meio da avaliacao da virulencia de 289 isolados monosporicos do patogeno. Foram utilizadas como diferenciadoras 10 linhagens elites do programa de melhoramento genetico de sorgo da Embrapa Milho e Sorgo. Os isolados de C. sublineolum foram obtidos de folhas de sorgo provenientes de Palmeira de Goias e Goiânia, GO, Sete Lagoas, Ipiacu e Uberlândia, MG, e Jardinopolis, SP e designados de acordo com um sistema binario de classificacao de racas. As populacoes foram tambem caracterizadas quanto a diversidade fenotipica, por meio de indices de Shannon, de Gleason e de Simpson, e de um indice de complexidade, e quanto a sua distribuicao e frequencia nas seis localidades. Somente a raca 31.04 foi encontrada nos seis locais avaliados e foi a raca mais frequente em Uberlândia, Ipiacu e Palmeira de Goias. A raca mais complexa, 31.31, foi a mais frequente em Sete Lagoas e Goiânia e nao foi observada somente em Palmeira de Goias. Verificou-se que as racas mais frequentes em cada localidade apresentaram-se, em sua maioria, bem distribuidas nas seis regioes avaliadas. O local com maior diversidade fenotipica foi Jardinopolis, de acordo com os indices de Shannon, Simpson e Gleason. O maior indice de complexidade de racas foi encontrado em Sete Lagoas e Goiânia, seguidas por Jardinopolis, Ipiacu, Uberlândia e Palmeira de Goias, respectivamente. Houve correlacao entre os indices de Shannon e Gleason, mas nao entre os indices de diversidade e de complexidade.

Resíduos de sorgo e a mineralização do nitrogênio em LATOSSOLO VERMELHO fase cerrado

Management alterations induce significant modifications on organic matter quality and quantity, on N quantity and forms and on the mineralization process. The aim of this work was to study the influence of straw on the N mineralization rates of the N-NH4+ and N-NO3 forms during the decomposition of residues of two sorghum genotypes. The experimental design consisted of a 3x2x3 complete block outline, including two soil managements, three cultural residues and two nitrogen levels, with three replications. Percolation tubes were prepared with 20 g of soil mixed with 20 g of sand. Each tube with soil and sand received 0.1g residual straw from the two sorghum genotypes, with and without 50 mg N kg-1 in the form of ammonium nitrate. A control treatment was maintained without straw in the presence and absence of N. After an initial seven day incubation period, N was extracted weekly, over 49 days, using 100 mL of 0.01 mol L-1 CaCl2. The forms N-NH4+ and N-NO3- were determined spectroscoptically (UV/VIS) in the percolated extracts. N mineralization dependent on sorghum genotype and applied N. Sorghum straw influenced time and amount of N mineralized. The N-NH4+/ N-NO3- ratio showed variability during the incubation time as influenced by the incorporated residue. That ratio increased up to fifteen days of incubation time and decreased in subsequent periods. Without residues the mineralization potential was higher in the N-NO3 form.

Resistance of Commercial Hybrids and Lines of Sorghum, Sorghum bicolor (L.) Moench., to Diatraea saccharalis (Fabr.) (Lepidoptera: Pyralidae)

Commercial sorghum hybrids and Embrapas lines were evaluated regarding resistance to sugarcane borer. Two field experiments were conducted in Sete Lagoas, MG, under natural infestation, during the second cropping season in a randomized complete block with 3 replicates. The plants were evaluated regarding to stand, maturity cycle, plant height, and number of broken or lodging stalks and yield. The borer incidence, number of galleries, number of healthy and damaged nodes were also evaluated to calculate the Infestation Index and Intensity Infestation Index. Among the commercial sorghum hybrids, Br 304 and CMSXS 9701 were the least infested wile Z 732 and Esmeralda were the least damaged. Among the lines, the least infested was 9815017 and least damaged 9816003. The two indexes were correlated positively with plant height in both experiments and negatively correlated with the lines cycle. However, there was no correlation between the Indexes for the hybrids. Among the lines the data fit to a logarithmic curve. Although there is a significant variability among commercial sorghum hybrids regarding sugarcane borer susceptibility, under high borer density, a significant yield loss can be computed to all hybrids. On the other hand, the genetic variability regarding sugarcane borer resistance among the sorghum lines indicated a significant potential for use in a breeding program of resistant cultivars.

Identification of sources of resistance in sorghum to Peronosclerospora sorghi

The main objective of this work was to identify sources of resistance in sorghum (Sorghum bicolor) to Peronosclerospora sorghi, the causal agent of downy mildew, through the evaluation of 42 sorghum genotypes under natural infection in the field. Genotypes were planted in single row plots between two rows of the susceptible line SC283, planted 30 days before, to act as spreader rows, in two separate nurseries. The experimental design was a completely randomized block design with three replications. Sorghum genotypes CMSXS156, CMSXS157, CMSXS243, TxARG-1, 8902, 9902054, 9910032, 9910296, Tx430, QL-3, SC170-6-17, CMSXS762 and BR304 were classified as highly resistant in both nurseries. Among these, SC170-6-17 and 9910296 showed 0% systemic infection. Results indicated the possible occurrence of different pathotypes of P. sorghi in the two nurseries.

Evaluation of genetic mixtures of sorghum lines for anthracnose resistance management

The main objective of this work was to evaluate the diversification of sorghum (Sorghum bicolor) populations as a way to manage resistance to the sorghum anthracnose fungus Colletotrichum graminicola. A total of 18 three-way hybrids were obtained by crossing six single cross male-sterile F1 hybrids, derived by crossing A (non restorer sterile cytoplasm) and B (non restorer normal cytoplasm) lines, with three fertile R (restorer) lines, previously evaluated for their differential reaction to the pathogen. Variation in the level of resistance was observed, as indicated by the values of the area under the disease progress curve (AUDPC) obtained for each hybrid. Lines contributed differently to the level of resistance of each hybrid. All hybrids in which CMSXS169R was the male progenitor were classified as highly resistant. Some hybrids had a level of resistance superior to the maximum levels of each line component individually.

Variability of the anthracnose fungus Colletotrichum graminicola in sorghum genotype mixtures

This paper reports partial results obtained on the variability of Colletotrichum graminicola developed in response to the host diversity generated by three-line combination of sorghum (Sorghum bicolor) genotypes. Nine sorghum lines were used in this study: CMSXS210B, CMSXS112B, CMSXS215B, CMSXS221B, CMSXS169R, CMSXS180R, CMSXS182R, CMSXS227R, and CMSXS116R. A total of 39 treatments on mixtures and pure stands of the component lines were evaluated in the field for the development of anthracnose, as a natural epidemic. Samples of the single spore isolates of the pathogen of each treatment indicated a reduction in the phenotypic diversity and an increase in the frequency of more complex races in genotype mixtures in relation to the pure stands of each genotype.

Padrões eletroforéticos das proteínas de reserva em grãos de sorgo com presença e ausência de tanino

Muitos metodos para determinar a presenca de taninos sao descritos na literatura, mas nenhum deles e universalmente aceito como ideal ou utilizado de forma unânime. Alguns metodos colorimetricos nao diferenciam taninos de outros compostos fenolicos, outros utilizam substâncias que nao sao adequadas como padrao. Metodos que utilizam a capacidade dos taninos de precipitar as proteinas podem causar resultados divergentes devido as diferencas na conformacao dessas moleculas. Assim, objetivou-se, neste estudo, identificar a presenca de taninos em 10 hibridos de sorgo atraves da analise de padroes proteicos obtidos por eletroforese. O metodo colorimetrico Azul da Prussia foi utilizado para quantificar os taninos nas amostras. A precipitacao das proteinas pelos taninos permitiu identificar os genotipos de sorgo com tanino atraves dos padroes proteicos das fracoes albuminas, globulinas e prolaminas. A analise eletroforetica das prolaminas mostrou que as bandas produzidas pelo polipeptideo kafirina, podem ser utilizadas na identificacao de sorgo sem tanino no grao.