Genetic Similarity Among Accessions of Paspalum notatum Flügge (Poaceae): a Potential to Parental Selection

HIGHLIGHTS Low genetic similarity in Paspalum notatum accessions. High genetic distance among diploid accessions. The accessions have good potential to breeding program.

Abstract Paspalum notatum is an important forage grass contributing significantly to the coverage of the natural fields of Southern Brazil. Simple sequence repeat (SSR) markers were used to evaluate the genetic similarity of strains within a P. notatum collection. Genomic DNA was extracted in bulk from young leaves of five plants from each accession obtained from the USDA. In the molecular analysis, the eight SSR markers evaluated formed seven distinct groups, and two isolated genotypes, with an average similarity index of 0.29, ranging from zero to 0.83. All the loci were polymorphic and the polymorphism information content ranging from 0.41 to 0.69. The results evidenced a low genetic similarity, which can be explored via parental selection in a breeding program.

Temperatures and substrates for germination and vigor ofErythroxylum pauferrense Plowman seeds

Erythroxylum pauferrense is an endemic understory plant species of the Northeast Region of Brazil. The species is of great importance to the region and so ecophysiological studies are needed for its preservation. The objective of the present study was to determine the best substrates and temperatures for testing germination and seed vigor of E. pauferrense. An experiment was performed comprising a completely randomized design in a 5 x 4 factorial scheme, with five temperature regimes (20, 25, 30, 35°C constant and 20-30°C alternating) and four types of substrates (paper, vermiculite, sand and commercial substrate). The following characteristics were evaluated: germination percentage, first germination count, germination speed index, mean germination time, seedling length and dry mass (root and shoot). Paper and vermiculite substrates combined with constant temperatures of 20, 25, 30 and alternated between 20-30°C, provide greater seed germination and vigor while 35°C reduces seed physiological quality.

Evaluation of fitness in F2 generations of Africa Biofortified Sorghum event 188 and weedy Sorghum bicolor ssp. drummondii

Background: Introgression of transgenes from crops to their wild species may enhance the adaptive advantage and therefore the invasiveness of and weedy forms. The study evaluated the effect of Africa Biofortified Sorghum (ABS) genes from ABS event 188 on the vegetative and reproductive features of the F2 populations derived from crosses with Sorghum bicolor subsp. drummondii. Results: F1 populations were obtained from reciprocal crosses involving ABS event 188 and its null segregant with inbred weedy parents from S. bicolor subsp. drummondii. Four F2 populations and four parental populations were raised in RCBD with 4 replications in a confined field plot for two seasons. Vegetative and reproductive traits were evaluated. The vigour shown in the F2 populations from the reciprocal crosses involving ABS event 188 and S. bicolor subsp. drummondii was similar to that in the crosses involving the null segregant and S. bicolor subsp. drummondii. Differences in vegetative and reproductive parameters were observed between the parental controls and the F2 populations. Examination of the above and below ground vegetative biomass showed lack of novel weedy related features like rhizomes. Conclusions: Therefore, release of crops with ABS 188 transgenes into cropping systems is not likely to pose a risk of conferring additional adaptive advantage in the introgressing populations. The interaction of ABS genes in weedy backgrounds will also not have an effect towards enhancing the weedy features in these populations.

Taxa de fertilidade de novilhas de diferentes grupos genéticos com primeiro serviço aos 14 meses de idade / Fertility rate of heifers of different genetic groups with 1st service at 14 months of age

Foram avaliadas as taxas de reconcepção de 98 novilhas primíparas (34 Guzerá - G, 32, 1/2 Guzerá x 1/2 Nelore - GN e 32,1/2 Red Angus x 1/2 Nelore - AN) com 14 meses de idade e peso médio de aproximadamente 249,65kg, criadas em pastos de Brachiaria brizantha cv Marandu. Na segunda estação de monta (EM), foram utilizadas apenas as 36 primíparas gestantes na primeira EM (três G, nove GN e 24 AN), com média de idade de 26 meses e peso corporal de 313,67±25,01kg, 336,50±45,84kg e 399,86±44,45kg, respectivamente, para as fêmeas dos grupos G, GN e AN. O grupo AN apresentou ganho médio diário (GMD) de 0,30±0,06 (kg/dia) e maiores taxas (58,33) de reconcepção (P<0,05), comprovando que a heterose resultante do cruzamento entre raças distintas com maior distância genética (Bos taurus taurus x Bos taurus indicus) proporciona maior desempenho produtivo e reprodutivo.

A total of 98 heifers of three genetic groups: 34 Guzerá (G), 32, 1/2 Guzerá x 1/2 Nelore (GN) and 32 1/2 Red Angus x 1/2 Nelore (AN), 14 month old and average body weight of 249,65kg, raised in Brachiaria brizantha cv Marandu were used to evaluate reconception rates. In the second breeding season (BS), only those 36 pregnant in the first BS (three G, nine GN and 24 AN), age 26 months and body weight of 313.67±25.01kg, 336.50±45.84kg and 399.86±44.45kg, respectively, G , GN and AN were evaluated. The highest reconception rate (58.33%, P<0.05) was registered for the AN group and showed that average daily gain of 0.30±0.06kg, showing that crosses between Bos taurus taurus x Bos taurus indicus leads to higher reproductive and productive performances.

Performance of beef cows of different genetic groups in natural and cultivated pastures / Pastagens naturais e cultivadas no desempenho de vacas de corte de diferentes grupos genéticos

The objective was to assess the performance of 96 pregnant cows of the genetic groups (GG) Charolais (C), Nellore (N), ½ CN and ½ NC, subjected to the following treatments: kept exclusively in natural pastures (NP) throughout the experimental period; kept in cultivated pastures (CP) from July 15 to Setp 15 (CPNP) or from Sept 15 to Nov 15 (NPCP) and the remainder of the experimental period in NP. The weight at the end of the first grazing period (Sept 15) was higher for the CPNP cows than those of the NPCP and NP. The weight at the end of the second period (Nov 15) was 456, 428 and 392 kg respectively for NPCP, CPNP and NP. At calving, the heaviest cows were the CPNP, followed by the NPCP and the NP. At weaning, 90 days postpartum, the heaviest were the NPCP, followed by the CPNP and NP. Nelore cows were less heavy in all evaluations, followed by C, with the F1s' weight higher than the purebreds. The grazing sequences did not affect the percentages of the cows in estrus and pregnancy, but did influence the invervals between calving and first estrus postpartum (ICE). The GG influenced the rate of cows in estrus, pregnant and the ICE which was lower in the F1 (103 days), followed by the C (109 days) and had the largest interval N (119 days). The grazing sequences affect the average daily weight gain (ADG) of calves until weaning at 90 days of age. The GG of the calf affected the ADG at to 210 days.

Objetivou-se determinar o desempenho de 96 vacas prenhas dos grupos genéticos (GG) Charolês (C), Nelore (N), ½ CN e ½ NC, submetidos aos seguintes tratamentos: mantidas exclusivamente em pastagens naturais (PN) durante todo o período experimental; mantidas em pastagens cultivadas (PC) a partir de 15 de julho a 15 de setembro (PCPN) ou a partir de 15 de setembro a 15 de novembro (PNPC) e o restante do período experimental em PN. O peso no final do primeiro período de pastejo (15 de setembro) foi maior para as vacas PCPN que as do PNPC e PN. O peso no final do segundo período (15 de novembro) foi de 456, 428 e 392 kg, respectivamente, para PNPC, PCPN e PN. No parto as vacas da PCPN foram mais pesadas, seguidas pela PNPC e a PN. Ao desmame 90 dias de pós-parto o grupo mais pesado era de vacas da PNPC, seguido pelo PCPN e PN. Vacas N foram menos pesadas em todas as avaliações, seguidas pelas C, com o peso dos F1s maior do que os puros. As seqüências de pastagem não afetaram os percentuais de vacas em cio e prenhes, mas influenciou os intervalos entre partos e pós-parto ao primeiro cio (IPC). O GG influenciou a taxa de vacas em estro, prenhes e IPC que foi menor nas F1 (103 dias), seguidas das C (109 dias) e as N tiveram o maior intervalo (119 dias). As sequencias de pastejo influenciaram o ganho de peso médio diário (GMD) de bezerros até a idade do desmame aos 90 dias de idade. O GG do bezerro afetou a GMD até os 210 dias.

Matrizes ovinas cruzadas são sempre mais eficientes do que as matrizes puras? / Are sheep crosses always more efficient than pure sheep?

Foi estudado o desempenho reprodutivo de 482 ovelhas multíparas (3/4 Texel x 1/4 Corriedale: TXC, 1/2 Romney Marsh x 1/2 Corriedale: RMC, 3/4 Poll Dorset x 1/4 Corriedale: PDC, 1/2 Finnish Landrace x 1/2 Merino Australiano: FLMA e Merino Australiano puras: MA), as características do crescimento de 585 cordeiros provenientes de carneiros Dorper e ovelhas: TXC (n = 68); RMC (n = 64); PDC (n = 68); FLMA (n = 183) e MA (n = 202) e os quilogramas de carne de cordeiros produzidos/kg de ovelha colocadas em cobertura (como indicador de eficiência), pastoreando campo natural e pastagens cultivadas. As ovelhas FLMA e TXC apresentaram as maiores taxas de parição (167,89 e 174,36%, respectivamente) em relação às demais cruzas, as quais não diferiram entre si (121,43 e 125,49%, PDC e RMC, respectivamente; P>0,05), porém foram superiores as MA (88,99%), sendo esse resultado uma consequência da maior quantidade de cordeiros nascidos/ovelha parida, que influenciou mais do que sua maior taxa de fertilidade. O genótipo da ovelha também afetou (P<0,0001) o crescimento dos cordeiros até o momento da sua venda com 41,6 ±6,7kg aos 206±7,25 dias de idade. Os cordeiros filhos das ovelhas TXC, PDC e RMC apresentaram maiores ganhos de peso diário que os filhos de FLMA, e esses maiores do que os MA. No entanto, de todas as cruzas avaliadas, somente a FLMA foi mais eficiente que a MA.

The reproductive performance of 482 multiparous ewes, with growth characteristics of 585 lambs from Dorper rams and ewes: 3/4 Texel x 1/4 Corriedale (TXC, n = 68); 1/2 Romney Marsh x 1/2 Corriedale (RMC, n = 64); 3/4 Poll Dorset x 1/4 Corriedale (PDC, n = 68); 1/2 Finnish Landrace x Australian Merino (FLAM, n = 183) and Australian Merino pure ewes (AM, n = 202) and kg of lamb produced/kg of sheep used in the service (as an indicator of efficiency), grazing natural and sown pastures, were studied. The TXC and FLAM sheep had the highest lambing percentage (167.89 and 174.36%, respectively) compared to the rest of the other crosses, and did not differ from each other (121.43 and 125.49%, PDC and RMC respectively, P>0.05), but were higher than AM (88.99%), due to the greater number of lambs born / ewe calving rather than their higher fertility. The type of ewe also affected (P<0.0001) lamb growth until its sale at 41.6±6.7 kg to 206±7.25 days of age, showing mothers of TXC lambs, PDC and RMC had higher daily gains than the FLAM and these more than those of MA. However, in all crosses tested, only FLAM was more efficient than MA.

Genetic divergence among maize hybrids in cerrado-pantanal ecotone / Divergência genética entre híbridos de milho no ecótono cerrado-pantanal

In maize breeding programs can arise difficulties in relation to combination capacity studies for determination of heterotic groups, which are highly correlated with genetic divergence among the parents. The aim of this study was to estimate the genetic divergence measured for nine quantitative morphological traits in eleven single-cross hybrids of maize cultivated in the Cerrado-Pantanal ecotone. The experiment was conducted at Universidade Estadual de Mato Grosso do Sul ­ University Unit of Aquidauana. The experimental design was a randomized blocks with four replications. At harvest time, it were measured the following traits: plant height, ear insertion height, ear length, ear diameter, stem diameter, number of kernels per rows, number of rows per ear, weight of hundred grains and grain yield. In the application of hybrids cluster technique was adopted the Mahalanobis's generalized distance as dissimilarity measure, and for establishment of similar groups was applied the Tocher's method. The results indicated the existence of genetic variability among tested hybrids. The greatest genetic divergence was observed among the pairs MAXIMUS and XB6012, implying in heterotic gains. Crossings of lines extracted from hybrids 2B587HX and XB6012 with lines obtained from the other hybrids provide greater heterosis. The traits grain yield and ear insertion height were those who more and less contributed, respectively, for genetic divergence among hybrids.

Em programas de melhoramento em milho podem surgir dificuldades quanto a estudos de capacidade de combinação para determinação de grupos heretóticos, que estão altamente correlacionados com a divergência genética entre os genitores. O objetivo deste trabalho foi estimar a divergência genética mensurada para nove descritores morfológicos quantitativos em onze híbridos simples de milho cultivado no ecótono Cerrado-Pantanal. O experimento foi conduzido na área experimental da Universidade Estadual de Mato Grosso do Sul, Aquidauana (MS). O delineamento experimental utilizado foi o de blocos casualizados com quatro repetições. No momento da colheita, foram mensurados os seguintes descritores: altura de planta, altura de inserção da primeira espiga, diâmetro da espiga, diâmetro do colmo, número de grãos por fileira, número de fileiras por espiga, massa de cem grãos e rendimento de grãos. Na aplicação da técnica de agrupamento de híbridos foi adotada a distância generalizada de Mahalanobis como medida de dissimilaridade, e para o estabelecimento de grupos similares foi aplicado o método de Tocher. Os resultados indicaram a existência de variabilidade genética entre os híbridos testados. A maior divergência genética foi observada entre os pares MAXIMUS e XB6012, implicando em ganho heterótico. Cruzamentos de linhagens extraídas dos híbridos 2B587HX e XB6012 com linhagens obtidas a partir dos demais híbridos proporcionaram maior heterose. Os descritores rendimento de grãos e altura de inserção da espiga foram os que mais e menos contribuíram, respectivamente, para a divergência genética entre os híbridos.

Capacidade de combinação e heterose em maracujazeiro amarelo / Combining ability and heterosis in yellow passion fruit

O objetivo deste trabalho foi determinar a capacidade geral (CGC) e específica (CEC) de combinação, bem como a heterose relacionada à produtividade e qualidade de frutos de maracujazeiro amarelo. Onze parentais foram cruzados em esquema de dialelo parcial (6 x 5). Os parentais e seus híbridos foram avaliados para as características: produtividade (PROD); número de frutos por parcela (NF); massa média de frutos (MF); rendimento de suco (REND); produtividade de suco (PRSUC) e teor de sólidos solúveis totais (SST). Foram observadas diferenças significativas para CGC, apenas dentro do grupo de parentais para todas as características, à exceção de PROD. Por outro lado, para CEC observou-se diferença significativa para todas as características. Dentre os componentes heteróticos, a heterose específica apresentou-se como mais expressiva, indicando presença de dominância e divergência genética entre alguns parentais dos dois grupos. Observou-se que os híbridos com maior heterose não foram os de maior média para a maioria das características. Como as interações que envolvem efeitos dominantes não são herdáveis, depreende-se que a exploração do uso de híbridos é uma estratégia viável no maracujazeiro amarelo, considerando a maioria das características relacionadas ao potencial produtivo e de qualidade de frutos.

The objective of this work was to determine the general (GCA) and specific combining ability (SCA), as well as the heterosis related to yield and fruit quality of yellow passion-fruit. Eleven progenitors were crossed in partial diallel squeme (6 x 5). Progenitors and hybrids were evaluated for: fruit productivity (FP); number of fruits per plot (NF); average fruit weight (FW); juice yield (JY); juice productivity per area (JPA) and total soluble solids (TSS). Significant differences were observed for GCA only within the group of progenitors for all characteristics, except for FP. However, for SCA, significant differences were observed for all characteristics. Among the heterotic components, the specific heterosis was the most important, pointing out the presence of dominance and genetic divergence among some progenitors of both groups. In many cases, it was also observed that the hybrids with high heterosis showed medium to low average for the traits. Since interactions with dominant effects are not inherited, the exploration of heterosis is a feasible strategy of yellow passion-fruit considering the most traits related to yield potential and fruit quality.

Inclusão da epistasia em modelo de avaliação genética de bovinos de corte compostos / The effect of the inclusion of epistasis on the genetic evaluation model of beef cattle composite

Dados de bovinos compostos foram analisados para avaliar o efeito da epistasia nos modelos de avaliação genética. As características analisadas foram os pesos aos 205 (P205) e 390 dias (P390) e perímetro escrotal aos 390 dias (PE390). As análises foram realizadas pela metodologia de máxima verossimilhança considerando-se dois modelos: o modelo 1 incluiu como covariáveis os efeitos aditivos diretos e maternos, e os não aditivos das heterozigoses para os efeitos diretos e para o materno total, e o modelo 2 considerou também o efeito direto de epistasia. Para comparação dos modelos, foram utilizados o critério de informação de Akaike (AIC) e o critério de informação Bayesiano de Schwartz (BIC), e o teste de razão de verossimilhança. A inclusão da epistasia no modelo de avaliação genética pouco alterou as estimativas de componentes de (co)variâncias genéticas aditivas e, consequentemente, as herdabilidades. O teste de verossimilhança e o critério de Akaike sugeriram que o modelo 2, que inclui a epistasia, apresentou maior aderência aos dados para todas as características analisadas. O critério BIC indicou este modelo como o melhor apenas para P205. Para análise genética dessa população, o modelo que considerou o efeito de epistasia foi o mais adequado.

Composite bovine data was analyzed with the objective of evaluating the effect of the epistasis parameter in the models of genetic evaluation. The analyzed characteristics were weight at 205 (W205) and 390 days (P390), and scrotal circumference at 390 days (SC390). The analysis were done by the maximum likelihood method, considering two models: model 1, which included as covariates the direct and maternal additive effects, and non-additive of the heterozygosis for the direct and total maternal, and model 2, which also considered the direct epistasis direct. The Akaike Information Criteria (AIC) and the Bayesiano of Schwartz Information Criteria (BIC) were used for the comparison of the models and the test of ratio of likelihood. The inclusion of the epistasis effects on the model of the genetic evaluation did not alter much the estimation of the genetic additive (co)variances components and, consequently the heritability. However, it was significantly superior by the likelihood ratio test for the studied characteristics. Through the BIC, model 2 was more adequate only for W205. For the genetic analysis of that population the model that considers the epitasis is the more adequate.

Combining ability of summer-squash lines with different degrees of parthenocarpy and PRSV-W resistance

The aim was to assess heterosis in a set of 16 summer-squash hybrids, and evaluate the combining capacity of the respective parental lines, which differed as to the degree of parthenocarpy and resistance to PRSV-W (Papaya Ringspot Virus-Watermelon strain). The hybrids were obtained using a partial diallel cross design (4 x 4). The lines of parental group I were 1 = ABX-037G-77-03-05-01-01-bulk, 2 = ABX-037G-77-03-05-03-10-bulk, 3 = ABX-037G77-03-05-01-04-bulk and 4 = ABX-037G-77-03-05-05-01-bulk, and of group II, 1' = ABX-037G-77-03-05-04-08-bulk, 2' = ABX-037G-77-03-05-02-11-bulk, 3' = Clarice and 4' = Caserta. The 16 hybrids and eight parental lines were evaluated for PRSV-W resistance, parthenocarpic expression and yield in randomized complete-block designs, with three replications. Parthenocarpy and the resistance to PRSV-W were rated by means of a scale from 1 to 5, where 1 = non-parthenocarpic or high resistance to PRSV-W, and 5 = parthenocarpic or high susceptibility to PRSV-W. Both additive and non-additive gene effects were important in the expression of parthenocarpy and resistance to PRSV-W. Whereas estimates of heterosis in parthenocarpy usually tended towards a higher degree, resistance to PRSV-W was towards higher susceptibility. At least one F1 hybrid was identified with a satisfactory degree of parthenocarpy, resistance to PRSV-W and high fruit-yield.

Embriões F1 (Hol X Gir) produzidos in vitro utilizados a fresco em rebanhos leiteiros comerciais e controlado / F1 Holstein (Friesan x Gir) embryos produced in vitro used fresh in commercial dairy herds and controlled herds

A importância do (F1) para o Brasil é notória, associando rusticidade e produtividade, porém é grande a dificuldade do produtor em manter seu rebanho nesse grau de sangue. No laboratório da Embrapa Gado de Leite em Juiz de Fora, MG foram produzidos in vitro 266 embriões (F1), a partir de complexos cumulus-oócitos (CCO's) de vacas Gir puncionadas e fecundadas com sêmen de touro Holandês. Destes, 53 embriões foram transferidos a fresco para receptoras de rebanhos comerciais de uma Cooperativa da Zona da Mata, MG, enquanto 72 embriões foram inovulados em rebanho controlado da Embrapa Campo Experimental de Coronel Pacheco. A produção de embriões F1 por fecundação in vitro apresentou taxa de produção de blastocisto de 15,58%. A taxa de gestação obtida foi de 26,4% no rebanho comercial e 40,2% no rebanho da Embrapa. Considerando-se o nascimento de 50% de machos e fêmeas, conclui-se que em rebanhos de 100 vacas seriam obtidas 13 fêmeas (13% de reposição) nos rebanhos comerciais e 20 fêmeas (20% de reposição) no rebanho da Embrapa. Foram muitas as dificuldades de operacionalização para o uso de dessa biotecnologia que requer um mínimo de escrituração zootécnica, controle sanitário, observação de cios e manejo reprodutivo.

The importance of (F1) to Brazil is notable, associating productivity and rusticity, it is difficult to the producer maintaining the herd in this blood degree. In Embrapa's Gado de Leite, laboratory in the city of Juiz de Fora, M.G., 266 embryos (F1) were produced in vitro from the oocytes of Gir cows, punched and fecundated with Holstein Friesan bull semen. Out of these, 53 embryos were transferred at natural into recipient cows in the commercial herds indicated by the technicians of a great cooperative of Zona da Mata's area, 72 embryos were transferred into recipients of Embrapa's herds under nutritional and sanitary controls. The remainder 139 embryos were frozen due to the lack of adequate recipient cows. The production of F1 embryos through in vitro fecundation of oocytes from Gir cows with semen from Holstein Friesan bull blastocist production rate of 15,58 %. The pregnance rate obtained was 26.4% in the cows from the commercial herds and 40.2% in the herds of Embrapa Gado de Leite. Considering the birth of 50% female cows, we can estimate a replacement annual rate of 13% (26.2% for gestation) for commercial herds and 20% (40% for pregnancy) for the controlled herd. There were many difficulties encountered in the operation, such as (i) the low level of adoption of technology; (ii) little investment in feeding, handling and sanity conditions of the herds; (iii) conditions capable to compromising the utilization of embryos, which requires a minimum of structure in terms of zoo-technical documentation, observation of rutting and reproduction management.

Genetic distance estimates among single cross hybrids and correlation with specific combining ability and yield in corn double cross hybrids

The objective of the present study was to correlate the genetic distances (GD) of single cross hybrids with yield, heterosis and specific combining ability (SCA) in the double cross hybrid synthesis. For this, 10 single cross commercial hybrids were used from different companies, and all the possible double hybrids were synthesized by a complete dialell. The hybrids were assessed in 15 locations in the 2005/2006 agricultural season, using the randomized complete block design with three repetitions. DNA was extracted from the single cross hybrids and 20 simple sequence repeat primers were used, nine of which were linked to the quantitative trait loci. It was ascertained that the single hybrids were superior in general to the double cross hybrids and that yield was highly correlated with heterosis and SCA (r = 0.75 and 0.82, respectively). There was no significant correlation between yield and GD (r = 0.25), but this index was at the limit of significance. There was a medium correlation between GD and heterosis (r = 0.40) and GD and SCA (r = 0.38). The intergroup hybrids placed by genetic grouping were generally more productive than intragroup hybrids, and the hybrids with GD greater than 0.84 had the maximum heterosis and SCA. It was concluded that the markers were efficient in placing hybrids in different heterosis groups and were also useful in eliminating the most negative heterosis and SCA.

Teste de tetrazólio para avaliação da qualidade fisiológica de sementes de melancia / Tetrazolium test in the evaluation of watermelon physiological seed quality

O teste de tetrazólio é um dos métodos mais promissores para estimar, de forma rápida, a viabilidade e ovigor das sementes. Sua utilização em sementes de melancia requer cuidados na embebição e manuseiopela presença de camada mucilaginosa aderente ao tegumento. O objetivo do trabalho foi definir o tempode embebição e do método de escarificação para retirada da mucilagem, no pré-condicionamento doteste de tetrazólio, sementes de diferentes cultivares de melancia. As sementes foram imersas em água a30oC por 12 e 18 horas, e escarificadas em cal, areia fina e areia grossa. Após corte longitudinal na porçãodistal ao eixo embrionário, os tegumentos foram retirados e os embriões permaneceram em água por mais2 horas a 30oC para remoção manual da membrana remanescente. Após definição do método ideal de précondicionamento,os embriões foram imersos em soluções de tetrazólio nas concentrações de 0,075%;0,5% e 1% por três e quatro horas a 30oC. A imersão das sementes de melancia em água a 30oC por 12horas, retirada da mucilagem com areia fina, corte longitudinal na porção distal ao eixo embrionário eremoção do tegumento, seguido da permanência dos embriões em água por 2 horas a 30oC para retiradamanual da membrana interna e imersão na solução de tetrazólio a 0,075% por 4h a 30oC são procedimentosadequados para avaliação da qualidade de sementes de melancia.

The tetrazolium test is one of the most promising methods to estimate in a fast way viability and vigor of seeds. Its usage in watermelon seeds requires some care with the imbibition and handling due to presence of mucilaginous layer adherent to the tegument. The objective of this research work was to define the imbibition time and the method of scarification for removing the mucilage, during pre – conditioning of the tetrazolium test in watermelon. Seeds from different watermellon cultivars were immersed in water at 30°C from 12 to 18 hours, and sloughed in cal, fine and thick sand. After longitudinal cut in the distal portion to the embryonic axis, the tegument was removed and embryos were kept in water for additonal 2 hours at 30°C for hand removal of the remaining membrane. After definition of the ideal pre – conditioning method, the embryos were immersed in tetrazolium solution in concentrations of 0,075%; 0, 5% and 1% for 3 and 4 hours at 30°C. The immersion of watermelon seeds in water at 30°C for 12 hours, mucilage removal with fine sand, longitudinal cut in the distal portion to the embryonic axis, and removal of tegument, followed by the permanence of embryos in water for 2 hours at 30°C for the hand removal of the internal membrane and immersion in the tetrazolium solution at 0,075% for 4 hours at 30°C are adequate procedures for the evaluation of watermelon seed quality.

Heteroses materna e individual para ganho de peso pré-desmama em bovinos Nelore Hereford e Nelore Angus / Maternal and individual heterosis for preweaning daily gain in Nellore Hereford and Nellore Angus cattle

Foram utilizados dados de 62.985 animais das raças Nelore, Hereford, Angus e produtos de cruzamentos Nelore Angus e Nelore Hereford de rebanhos comerciais a fim de estimar os efeitos de heterose materna e individual para o ganho médio diário no período pré-desmama (GMD). Os valores obtidos de heterose individual e materna considerando-se o valor médio de GMD da população representam um acréscimo de 6,2 por cento e 11,2 por cento no GMD para os animais F1 e filhos de vacas F1, respectivamente. A heterose materna correspondeu a 64,5 por cento da heterose total. Animais cruzados Bos taurus Bos indicus obtêm GMD maior do que o dos animais das raças puras.

A priori choice of hybrid parents in plants

Plant breeding deals with high-yielding genotypes. However, how best to choose parents of these genotypes remains an unsolved question. Here, we focus on a priori choice based on parental distances by means of agronomic and molecular data. Despite numerous theoretical and empirical studies, a priori choice continues to be a controversial procedure. Both success and failure are commonly reported. We looked at these ambiguous results in order to investigate their possible causes. A total of 139 articles on genetic divergence were sampled to examine aspects such as type and number of markers utilized. We suggest that the mean number of 160, 281 and 25 for RAPD and RFLP markers, and SSR loci, respectively, which we found in these papers, should be increased for accurate analysis. A second sample composed of 54 articles was used to evaluate the divergence-heterosis association. Most of them (28) detected positive divergence-heterosis association, whereas 26 revealed negative or inconclusive results. We examined several causes that influence a priori choice positively and negatively.

Estimación de Algunos Efectos Genéticos de la Trucha Arcoiris (Oncorhynchus Mikiss) a Partir de un Cruzamiento Dialélico Completo de dos Líneas: I. Fertilidad y Supervivencia / Valuation of some genetic effects of rainbow trout (Oncorhynchus mikiss) from a complete diallelic cross of two lines: I. Fertility and viability

El presente estudio se realizó en el Centro Acuícola "El Zarco", Estado de México, México, para evaluar el comportamiento reproductivo de dos líneas de truchas Arcoiris (Oncorhynchus mikiss), la línea Zarco ("Z") y la línea Jilotzingo ("J"). Con el propósito de estimar efectos genéticos, se utilizó el cruzamiento dialélico, que permite la mediación de la respuesta a la heterosis y a la habilidad combinatoria general y específica, entre las diferentes líneas utilizadas y cruzadas recíprocas. Al evaluar la incubación, fertilidad, viabilidad y moralidad en las etapas de alevinaje y crianza, se encontró una mejor fertilidad para la línea Jilotzingo; la mortalidad presentada en la etapa de alevinaje fue más elevada en los grupos genéticos híbridos (12.65 por ciento) respecto de los puros (2.6 por ciento). La mortalidad durante la etapa de crianza fue mayor en el grupo genético Z x J (6.5 por ciento) con respecto a los otros. Los resultados muestran que no existe heterosis para estas características y que es importante seleccionar líneas maternas con el fin de incrementar la fertilidad

Comparative performance of six holstein-friesian X guzera crossbred groups in Brazil: health costs of calves

Costs of drugs for pneumoenteritis and plasmosis treatment were evaluated in 614 bucket reared female calves of six Holstein-Friesian (HF) x Guzera crossbred groups (1/4 to > 31/32 HF gene fraction). Important heterosis effects resulted in lowest health costs for F(l) (US$ 4.33 per calf) and highest costs for > 31132 HF calves (US$ 8.01).

Diallel among twenty eight varieties of maize

Twenty eight varieties of maize of different maturities and types of endosperm were assessed together with 378 F(1), and seven commercial hybrids (controls) in three locations: Sete Lagoas, MG, Goiânia, GO, and Londrina, PR. The varieties represent germplasms adapted to different areas of Brazil,used in the breeding program at the National Maize and Sorghum Research Center at Sete Lagoas, MG. The joint analysis of variance for ear weight showed significance (P < O.O1) for environments, entries, varieties, heterosis, mean heterosis, variety heterosis, specific heterosis, environments x entries and environments x varieties. The average yield of the varieties varied from 2,322 to 7,704 kg/ha, while for the intervatietal hybrids the variation was from 4,112 to 8,363 kg/ha. The mean heterosis was 489 kg/ha and the varietal heterosis varied from -589 to 1,339 kg/ha. The highest specific heterosis was obtained for the BR 105 x BA III - Tusón crossing. Some intervarietal hybrids were higher yielding than the best control. This is promising for breeding purposes, since new synthetic varieties can be formed or used to begin programs to produce hybrids. No association was found between heterosis and endosperm type.

Heterose em suínos na fase de aleitamento / Heterosis in pre-weaning traits in swine

Visando avaliar o ganho de produtividade, advindo da heterose, no peso de suínos em fase de aleitamento, analisaram-se os pesos ao nascimento (PO), 21 dias de idade (P21) e desmama (PD) de 746 leitöes, sendo 201 da raça Landrace, 136 Wessex-Saddleback e 409 mestiços, pelo método dos quadrados mínimos, considerando-se, ainda, os efeitos fixos de época e ano de nascimento, ordem do parto, sexo do leitäo e tamanho da leitegada, além da raças paterna e materna e suas interaçöes. Os efeitos näo genéticos tiveram influência significativa em quase todas as características. Os mestiços mostraram, em geral, pesos superiores aos puros, com estimativas de heterose de 2,6 por cento para PO, 9,7 por cento para P21 e 13,9 por cento para PD, indicando a importância da herança näo aditiva à medida que os leitöes ficam menos dependentes de suas mäes. Os efeitos de interaçäo entre as raças paterna e materna foram cada vez maiores com o avançar da idade. Os resultados indicam haver ganho de produtividade com a utilizaçäo deste tipo de cruzamento