Clibas Vieira

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.

Foliar application of molybdenum in common bean. II. Nitrogenase and nitrate reductase activities in a soil of low fertility

Abstract Foliar application of molybdenum (Mo) at 40 g ha‐1 25 days after plant emergence greatly enhanced nitrogenase and nitrate reductase activities of common bean (Phaseolus vulgaris L.), resulting in an increase in total nitrogen (N) accumulation in shoots. Application of 20 kg N ha‐1 as ammonium sulfate [(NH4)2SO4] at sowing decreased nodulation and nitrogenase activity. Rhizobium inoculation did not affect nitrogenase activity which demonstrated that Mo application increased the efficiency of native Rhizobia strains. Nitrogen amendment, either at planting (20 kg N ha‐1) or as a side dressing (30 kg N ha‐1) 25 days after plant emergence, did not affect the foliar nitrate reductase activity. Molybdenum foliar spray as ammonium molybdate [(NH4)6Mo7O242H2O] and N applied as a side dressing increased equally the total amount of N in the pods. A 10% increase in the seed N concentration was obtained with foliar application of Mo, while N applied as a side dressing had no effect on seed N concentration. An...

Molecular and embryonic evidence of apomixis in cassava interspecific hybrids (Manihot spp.)

In cassava, apomixis could fix hetereozygosity and prevent the transmission of systemic pathogens which complicate vegetative propagation of the crop. Evidence from maternal inheritance of RAPD markers and the structure of the embryonic sac in large progeny sets of two distinct genotypes have further confirmed that apomixis occurs in cassava. Here, we have built on an earlier report of apomixis in cassava in four ways (1) we estimated the rate of faculative apomixis in the range of 2% (2) we detected the occurrence of apomixis in a second genotype, derived form a different interspecific cross; (3) apomictic behavior was demonstrated in an F1 individual and (4) embryonic evidence showed that the mode of apomixis is aposporic. Since apomixis was detected in an F1 interspecific hybrid it is possible that genes for apomixis could be transferred directly to cultivated cassava from a wild relative. Key words: Cassava, interspecific hybrid

Evidence of apomixis in cassava (Manihot esculenta Crantz)

Apomixis maintains heterosis and avoids transmission of systemic pathogens which accompany vegetative propagation of cassava. An embryonic study of cleared ovules of two cassava clones in toto showed them to be of aposporic nature. Cytogenetic analysis of the two clones revealed an aneuploid structure (2n + 1) in apomictic individuals, whereas it was 2n in the sexually reproduced plants.

Adubação nitrogenada e molíbdica da cultura do feijão na Zona da Mata de Minas Gerais

Three series of experiments were carried out. In the first, the effects of N, Mo, and rhizobium were studied at two municipalities; in the second, conducted at another municipality, a factorial with four rates of N (0, 30, 60, and 90 kg ha-1) and four rates of Mo (0, 40, 80, and 120 g ha-1) was studied; and in the third, at six municipalities, the following combinations of N at planting time (kg ha-1), N as side dressing (kg ha-1) and Mo (g ha-1) were used, respectively: 0-0-0, 0-40-70, 20-0-70, and 20-40-70. In all experiments, Mo (as foliar spray) and N (as side dressing) were applied at about 25 days after plant emergence. Ordinary superphosphate (90 kg ha-1 of P2O5) plus potassium chloride (60 kg ha-1 of K2O) were applied as uniform fertilization for all experiments. The soils were contaminated by native strains of Rhizobium. Inoculation with selected strains of Rhizobium had no effect on grain yield. Molybdenum fertilization increased bean yield, and maximum yields were attained with 70 to 100 g ha-1 of Mo, depending on N fertilization: smaller rate of Mo was needed when greater dose of N was used and vice versa. Nitrogen applied at planting time was also essential and its absence could not generally be compensated by side dressing application. The N + Mo combination increased bean yield in approximately 90 to 200%.

A molecular and embryonic study of apomixis in cassava (Manihot esculenta Crantz)

In cassava, apomixis fixes heterosis and avoids transmission of systemic pathogens which complicate vegetative propagation of the crop. A combination of evidence from maternal inheritance of RAPD markers and the structure of the embryonic sac in large progeny sets of two distinct genotypes have further confirmed the occurrence of apomixis in cassava. We could advance further on earlier reports of the detection of apomixis in four ways: (1) we could arrive at an estimate of the rate of facultative apomixis in the range of 2%; (2) we detected the occurrence of apomixis in a second genotype, derived from a different interspecific cross; (3) apomictic behavior was demonstrated in an F1 individual and (4) parallel embryonic evidence was generated that corroborate the potential occurrence of apomixis by apospory. The fact that apomixis was detected in an F1 interspecific hybrid hints to the possibility of directly transferring genes for apomixis from a wild relative to cultivated cassava.

Overcoming crossing barriers between cassava, Manihot esculenta Crantz and a wild relative, M. pohlii Warwa

The use of mentor pollen has enabled successful hybridization between cassava, Manihot esculenta Crantz, and the wild species M. pohlii Warwa. Killed pollen of a cross compatible type produced by freeze-thawing was mixed with incompatible pollen and the mixes were dusted on stigmas. This treatment resulted in production of seed in 4.9% of the total pollinations, compared to 0% in the case of untreated pollinations. The use of a bridge species, M. neusana Nassar, through the hybrid M. pohlii and M. neusana also proved successful in overcoming interspecific barriers between cassava and M. pohlii.

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.

Divergência genética em feijoeiro em condições de inverno tropical

This work aimed to evaluate the genetic divergency among tolerants and non tolerants parents to cold and their hybrid combinations. The generalized distance of Mahalanobis, the method of cluster analysis proposed by Tocher and the canonical variability technic were the multivaried proce- dures used. Common bean cultivars of two different groups were used in the crosses, being Vermelho 2157, Ouro Negro, Antioquia 8 and Ricopardo 896 the cultivars tolerant to cold, and the commercial cultivars EMCAPA 404 - Serrano, Carioca and EMCAPA 405 - Goytacazes the non tol- erant ones. The parents and the hybrid combinations in the F 1, F2 and F3 generations were evaluated in Coimbra, Minas Gerais on four experiments, in 1995 and 1996. The genetic divergency among the genetic resources evaluated were influenced by temperature and advancement of the generations. The most dissimilar cultivars were Antioquia 8 and EMCAPA 404 - Serrano and Ouro Negro and Ricopardo 896 were the most similar cultivars. Grain yield and number of pods per plot were the less important characteristics influencing on genetic divergency. However, as they showed low genotypic correlation with the other characteristics and were of the greatest importance on yield, they can not be despised.

Idade de colheita do feijão-vagem anão cultivar Novirex.

Foram conduzidos tres ensaios, dois em Vicosa e um em Coimbra, municipios da Zona da Mata de Minas Gerais, com o objetivo de se determinar a melhor idade de colheita do feijao-vagem cv. Novirex, de habito de crescimento determinado (tipo I). Em Vicosa, os ensaios foram instalados em 16/04/97 e 12/08/97 e em Coimbra, em 19/03/98. Irrigacao e controle de insetos foram feitos quando necessarios. Foi utilizado o espacamento entre fileiras de 0,5 m, com aproximadamente 15 sementes por metro. Foram avaliadas cinco idades de colheita, em intervalos de dois a quatro dias. A primeira colheita foi realizada antes do final da floracao, quando havia muitas vagens comerciais por planta e nenhuma vagem fibrosa. Em Vicosa (semeadura em 16/04/97), os maiores rendimentos de vagens comerciais (entre 8,6 e 10,1 t/ha) foram alcancados entre 63 e 71 dias apos a emergencia (DAE). No outro ensaio de Vicosa (semeadura em 12/08/98), os maiores rendimentos foram obtidos aos 56 e 60 DAE (7,4 e 7,7 t/ha, respectivamente). Em Coimbra, as colheitas realizadas aos 46 e 49 DAE proporcionaram os rendimentos mais altos (8,1 e 8,4 t/ha, respectivamente). A ausencia de flores ou presenca de pouquissimas flores foi um indicativo da melhor epoca de colheita da cv. Novirex visando maximizar o rendimento de vagens comerciais, independentemente da epoca de plantio. Nesta fase dos feijoeiros, as vagens, em media, haviam atingido o desenvolvimento maximo.