Valter Rodrigues Oliveira

Análise de trilha sob multicolinearidade em pimentão

The main goals of this work were: a) to display genotype correlations in direct and indirect effects of primary and secondary components on the production of fruits, in green pepper (Capsicum annuum L.) genotypes, by mean of path analysis; b) to compare alternative methods of estimation of the path coefficients to avoid the adverse effects of multicollinearity. Based on the magnitude of direct and indirect effects, none of the primary or secondary components showed to be more important in the selection of more productive genotypes. In segregating populations, the character height of the plant might be useful in correlated response, by means of indirect selection. In the occurrence of moderate to severe multicollinearity between the characters, the elimination of variables from the regression model and the ridge path analysis showed to be efficient in reducing the high variances of the path coefficients found. However, when several variables need to be eliminated, the disposal process becomes difficult and many analysis might be necessary. Ridge path analysis, although, should by-pass the adverse effects of multicollinearity, without having great reduction on the coefficient determination values of the regression models.

Combining ability for nodulation in common bean (Phaseolus vulgaris L.) genotypes from Andean and Middle American gene pools

Ten F1s obtained from crosses among five common bean genotypes of Andean (WAF 15, Mineiro Precoce and Batatinha) and Middle American (BAT 304 and Ouro) gene pools were assessed for their combining abilities for root nodulation with Rhizobium tropici strain CIAT 899. The plants were grown under controlled conditions and evaluated for number of nodules per plant (NN), nodule dry weight (NDW), mean nodule weight (MNW) and plant fresh weight (PFW). The subdivision of the treatment effects on the general (GCA) and specific combining effects (SCA) were performed according to Griffings diallel analysis method 2, model 1. The analyses of variance and estimates of quadratic components showed that non-additive gene effects were more important in the expression of NN and PFW, whereas additive gene effect was predominant for NDW and MNW. A close association was observed between high number of nodules and GCA. Generally, crosses involving parents of different gene pools yielded hybrids with high positive estimates of SCA for all assessed traits. The genotypes of Andean origin WAF 15 and Mineiro Precoce are the most promising parents for breeding programs to increase NN and NDW in common beans.

Adaptabilidade e estabilidade de cultivares de milho-pipoca na região centro-sul do Brasil

Este trabalho teve como objetivo estudar a adaptabilidade e estabilidade de cultivares de milho-pipoca avaliadas pela Embrapa-Centro Nacional de Pesquisa de Milho e Sorgo, no ano agricola 1991/92. Foram avaliadas 15 cultivares em 19 locais quanto a produtividade, e em 15 locais quanto ao indice de capacidade de expansao (ICE) na regiao centro-sul do Brasil. As cultivares GO 100P, MF 1001, Pirapoca-Amarela, Pirapoca-Branca e Colorado Pop 1, foram mais promissoras, pois apresentaram boas medias de produtividade (1.700 a 2.100 kg/ha de graos) e razoaveis ICE (17 a 21 mL/mL). Quanto a variavel produtividade, as cultivares Pirapoca-Amarela e Colorado Pop 1 apresentaram-se adaptadas a ambientes favoraveis, e foram estaveis. As cultivares MF 1001, Pirapoca-Branca e GO 100P, demonstraram capacidade satisfatoria no aproveitamento dos estimulos ambientais, e foram estaveis. Todas foram estaveis em relacao ao ICE, e as cultivares MF 1001, Colorado Pop 1, Pirapoca-Amarela e Pirapoca-Branca demonstraram capacidade satisfatoria no aproveitamento dos estimulos ambientais. A cultivar GO 100P foi melhor adaptada para ambientes favoraveis.

Reaction of tomato hybrids carrying the Ty-1 locus to Brazilian bipartite Begomovirus species

The number of tomato-infecting begomoviruses has increased in Brazil after the introduction of the polyphagous vector Bemisia tabaci biotype B. The Ty-1 locus, introgressed from Lycopersicon chilense, controls tolerance to species of the monopartite Tomato yellow leaf curl virus (TYLCV) complex in Europe and the Middle East. However, little information is available about the Ty-1 effectiveness against species of the bipartite Begomovirus complex occurring in Brazil. Heterozygous (Ty-1/ty-1) and homozygous (ty1/ty-1) hybrids were evaluated for reaction to Begomovirus isolates under open field conditions in two growing areas in Central Brazil. Test plants were evaluated under natural inoculation with high vector pressure. Evaluation was done using a disease assessment scale (DAS) varying from 1= no symptoms to 4= severe symptoms. Systemic infection was evaluated via polymerase chain reaction (PCR) using ‘universal’ Begomovirus primers. In the trial #1, the hybrids (Ty-1/ty-1) and (ty-1/ty-1) had 35% and 95% of plants with symptoms and 75% and 100% of plants with positive PCR, respectively. In the trial #2, only 20% of the Ty-1/ty-1 hybrid plants were symptom-free with both hybrids displaying 100% of plants with positive PCR. This reaction of the Ty-1 hybrid to bipartite Begomovirus species was similar to that reported in Europe and the Middle East to the TYLCV complex with a large number of plants being neither virus-free nor symptom-free. On the other hand, symptom expression of the Ty-1 hybrid was significantly milder than ty-1/ty-1 hybrids in both trials (DAS = 1.35 vs. 2.70 for the trial #1 and DAS = 2.05 vs. 3.95 for the trial #2). Nucleotide sequencing indicated the presence of isolates genetically related to Tomato rugose mosaic virus (ToRMV) in the trial #1 and a mixed infection of ToRMV and Tomato yellow vein streak virus in the trial #2. Therefore, the Ty-1 locus seems to control a “tolerance” response to distinct Begomovirus species. Resistance gene clusters is a common feature in the tomato genome, particularly at the chromosome 6 where Ty-1 is located. Therefore, additional studies are necessary to confirm if this tolerance to a range of begomoviruses is controlled by Ty-1 alone or a by the action of distinct, closely linked genes.

Desafios e oportunidades para o agronegócio da cebola no Brasil

The challenges and the oportunities for the onion agribusiness The main objective of this work was to describe some socieconomic aspects of the onion production in Brazil and to detect the principal challenges and opportunities for the onion agribusiness. The onion cultivation in Brazil is a family activity (88%), generating about 250 thousand jobs directly involved in the production. The onion consumption in Brazil is nearly 85 thousand t per month. With the consolidation of the MERCOSUL, the onion import from Argentina and the national production has caused excess of supply in some months, generating losses and consequent damages for the producers. The Brazilian productive sector needs to improve the technological level of the onion production to reach greater technical and economic efficiency. However, it is necessary that Brazilian and Argentinian producers look for a better production forecast to avoid excess of supply during some periods of the year.

Similaridade genética entre cultivares de cebola de diferentes tipos e origens, baseada em marcadores AFLP

The genetic similarity among onion cultivars of different origins was evaluated, in order to carry out genetic resources and breeding programs for this species on the Brazilian Northeast. Forty-one onion cultivars were analyzed for 146 polymorphic Pst1/Mse1 AFLP bands, according to UPGMA phenogram, built with the Jaccards similarity coefficient matrix. The phenogram co-phenetic value was estimated in 0.91 showing a good adequacy of the data. In the phenogram were observed two main onion groups at the cut point of 0.55 of similarity: 1) group composed of predominantly Brazilian cultivars, with some inclusion of foreigners; and 2) group with three foreign cultivars (Mercedes, Perfect and TEG 502 PRR). Rijnsburger Jumbo and IPA 8 presented the largest similarity (85%), while Madrugada presented the greatest dissimilarity to the other cultivars. The cultivars developed by IPA were split in sub-groups within the group 1: IPA 8, IPA 10 and IPA 11; IPA 12, IPA 7, IPA 2 and IPA 6; IPA 3, IPA 4 and IPA 9, suggesting that genetic variability could be explored by crosses among cultivars from different IPA subgroups. Bola Precoce and BRS Cascata presented the greatest similarity among the Brazilian cultivars. A similarity greater than 39% was observed, suggesting a high genetic variability of the analyzed onion collection. Introduction of new cultivars should take in consideration other origins than USA, in order to increase the genetic variability of onion germplasm in the Northeast Brazil.

Caracterização molecular de cultivares de cebola com marcadores microssatélites

The objective of this work was to establish allelic patterns and to estimate genetic distances based on the SSR marker in 44 onion cultivars adapted to Brazils tropical and subtropical growing conditions. An UPGMA dendrogram generated from the distance matrix of the Jaccards coefficient, based on 40 alleles of 13 SSR loci, was used for visualizing genetic similarities. Total DNA was extracted according to the CTAB 2x protocol, and the PCR products were analyzed in 6% denaturing polyacrylamide gels and stained with silver nitrate. The number of base pairs was estimated by the inverse mobility method, based on regression of products of known size. The heterozygosity mean was 0.58 for all SSR loci. The 40 alleles of the 13 SSR loci were enough to distinguish all 44 onion cultivars. The highest number of common alleles was observed between Yellow Granex and Henrys Special PRR cultivars, and the lowest was observed between the Baia Periforme Super Precoce and Excel cultivars. The seven main groups of onion cultivars identified in the dendrogram were in agreement with the known genetic genealogy and with the agronomic type of the analyzed cultivars. The selected SSR loci are adequate for breeding programs and for protection of the cultivars of the species.

Mungbean cultivation in summer in Viçosa and Prudente de Morais, Minas Gerais State, Brazil

We evaluated 25 genotypes of mungbean in the summer in Vicosa (sown in December 1997) and Prudente de Morais (sown in January 1999): nineteen lines from the Asian Vegetable Research Development Center, four from the Instituto Nacional de Pesquisa da Amazonia, one cv. from Peru besides cv. Ouro Verde. Yield varied from 1.2 to 2.0 t/ha in Vicosa, and from 1.3 to 2.6 t/ha in Prudente de Morais. Several lines yielded more than the cultivar Ouro Verde, standing out the line VC 3984-B-2-B-4-1-B due to the resistance to prostration. Mungbeans were well adapted in the summer season providing high yield in relatively short time.

CAPACIDADE DE COMBINAÇÃO ENTRE LINHAGENS DE PIMENTÃO DIFERINDO NA TOLERÂNCIA AO BAIXO TEOR DE FÓSFORO NO SOLO

Six lines of sweet pepper (Capsicum annuum L.) differing in tolerance to low phosphorus (P) content in the soil, their F1 hybrids and reciprocals, obtained from a complete diallel cross, were assessed under greenhouse conditions in order to estimate their combining abilities for total dry matter accumulation (shoot) dry matter, root dry matter, root (shoot) ratio, leaf area, plant height, total P content in the plant and P translocation coefficient. Both general (GCA) and specific (SCA) combining abilities were statistically significant with quadratic component associed to SCA which was always greater in magnitude than GCA for all traits, showing a predominance of non-additive genic effects in crosses. In addition to high positive GCA estimates, the tolerant lines to low P availability were the most divergent and their hybrids showed high average values for most of the assessed traits, while an opposite behaviour was observed in the tolerant lines. Considering the performance of the lines, the heterosis and the SCA effect, the following are promissing combinations: P-141-190--F16 x P-142-403-F11, P-142-215-F15 x P-142-270-F12, P-141-152-F14 x P-142-215-F15, P-141-152-F14 x P-142-403-F11 and P-141-150-F10 x P-141-152-F14. No difference was found among reciprocal crosses in relation to the assessed traits.

Tolerância de genótipos de pimentão ao baixo teor de fósforo no solo

Twenty two genotypes of sweet pepper (Capsicum annuum L.) were grown in pots containing 2.45 dm3 soil, in which six phosphorus (P) levels were applied (25, 50, 100, 200, 300 and 600 mg.dm-3 P). For each P level, the genotype performance was evaluated according to the characteristics expressing growth and nutritional efficiency. For several P levels, there was an occurrence of great differences among genotypes either in total dry matter accumulation and other characteristics related to growth, whereas low differences were observed in the nutritional characteristics. Among all P levels applied, 200 mg.dm-3 P was the most adequate for both identification of genotypes which are tolerant to low P availability and genetic studies, for its experimental accuracy and greater genotypic variability provided. By comparing the averages of total dry matter and based on discriminatory functions (multivariate analysis technique proposed by T. W. Anderson), six genotypes were identified as tolerant, ten as moderately tolerant and six as intolerant to low P contents. Apparently, only one factor was responsible for the difference in growing, which was observed between tolerant and intolerant genotypes. The tolerant genotypes which showed to be 2.34 times more efficient in producing total dry matter, also accumulated 2.38 times more P in the average, than those intolerant, probably due to greater biomass of tolerant-genotype roots. Differences in internal P use did not contribute for the differences between tolerant and intolerant genotypes.