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Alfonso José Lag-Brotons, José Martín Soriano-Disla, Ignacio Gómez and José Navarro-Pedreño

Cynara cardunculus L., known as cynara for industrial application, is a versatile plant for Mediterranean regions. Irrigation with non-conventional salty water sources is a common practice in these water-scarce regions. However, the research performed on cynara salt-stress response is limited and solely tested under soilless conditions. Thereby, the aims of the current experiment were to ascertain the effect of saline irrigation on cynara growth and mineral nutrition in Mediterranean soils. The influence of soil was considered using two typical agricultural soils, mainly differing in their salinity status. Plants were grown under controlled conditions from November until July in pots filled with soil amended with sewage sludge compost. Three saline irrigation treatments were applied (0.7, 2, and 3 dS·m−1) with increasing concentrations of NaCl (4, 13, and 23 mM). Saline irrigation started in January and ended in June. Plants growth parameters (height, dry biomass, heads number, seed yield) declined with saline irrigation. Aboveground dry biomass of plants irrigated with 3 dS·m−1 was reduced approximately one-third regarding the control value, whereas seed yield was reduced in 57%. Despite growth reduction induced by salinity, no symptoms of nutritional deficiency were observed in leaves. Saline irrigation was the main driving factor regarding cynara mineral concentration, except for potassium (K) and manganese (Mn), which were related to soil type. Chlorine (Cl) and sodium (Na) concentration increased at the whole-plant level, whereas magnesium (Mg) showed the opposing trend. Similar trends were observed in the mineral content of cynara aboveground biomass. Interaction effects between soil type and saline irrigation were marginal. Cynara exhibited high K selectivity, which might be associated with a mechanism of salt tolerance, whereas Mg is suggested as a potential indicator of salt stress in cynara plants grown in calcareous Mediterranean soils. We concluded that cynara growth and mineral nutrition were mainly affected by saline irrigation, probably as a result of the accumulation of Na and Cl.

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Orlanda Cristina Barros Moreira, José Martins, Luís Silva and Mónica Moura

Prunus azorica is an Azorean endemic tree considered as a priority species for conservation. It is important as a laurel forest component, particularly at medium altitude, and as a food source for the endangered bird Pyrrhula murina. The best conditions for seed germination were investigated after removal of the outer layers of the fruit by determining the effect of 1) using stones or seeds; 2) stratification regime (six treatments and a control); 3) incubation temperature (four alternating temperature regimes); and 4) gibberellic acid concentration (three levels). This resulted in a fully factorial design with 168 (2 × 7 × 4 × 3) treatments with three replicates per treatment and 25 seeds per replicate. Cumulative germination percentages were determined at the end of the trial. Globally, there was a significant effect of endocarp removal (49% germination with seeds and 15% with stones). Both for stones and seeds, there was a significant effect of incubation temperature, stratification regime, and growth regulator concentration. Stones attained a maximum germination of ≈80% under several stratification treatments including cold (4 °C) or warm (20 °C) followed by cold and at 10/5 °C without the addition of a growth regulator. Seeds attained a maximum germination of greater than 90% without stratification at 10/5 or 15/10 °C without the addition of a growth regulator. During the stratification process, germination occurred only for seeds, particularly for longer treatments, for example, those corresponding to 3 or more months of stratification, including warm followed by cold (75% to 80%) or cold alone (77%). According to seed morphology and germination results, the seed appears to have a non-deep physiological dormancy. Seeds of P. azorica can thus be efficiently germinated after endocarp removal at temperatures of 10/5 or 15/10 °C with a daily light period of 12 hours. This protocol allowed producing hundreds of viable seedlings that were used in the reforestation of a laurel forest stand in a LIFE project.

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Juan Bernardo Pérez-Hernández and María José Grajal-Martín

In vitro culture of immature embryos may assist mango breeding in the production of hybrid plant material. However, zygotic embryo culture techniques have not been successfully developed for mango. To recover in vitro zygotic plants through embryo culture, ‘Lippens’ and ‘Keitt’ were used as a source of model immature embryos. Excised embryos were incubated in a liquid maturation medium to test different culture systems and media composition. Subsequent germination allowed for the recovery of complete in vitro plantlets. Variables included during artificial embryo maturation, independently or through paired interactions, significantly affected all the parameters measured for embryo development and characterization of the plantlets. Main effects of culture system (i.e., static versus agitation) and coconut water supply (20%) were responsible for up to 85.5% of total treatment variation. Direct and inverse interactions observed between culture system and either coconut water supplement or sucrose content (45 or 60 g·L−1) contributed to define the best combination of factors to improve embryo growth and plant formation. Complete plantlets could be obtained at a frequency above 83% for both cultivars at the end of the in vitro phase at a developmental stage that allowed acclimatization to greenhouse conditions.

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Víctor Galán Saúco, María José Grajal Martín, Domingo Fernández Galván, Águeda Coello Torres, José Juárez and Luis Navarro

A putative polyploid seedling tree appeared among the polyembryonic mango (Mangifera indica L.) `Gomera-1', widely used as a rootstock in the Canary Islands. Initially detected because of its wider and more coriaceous leaves, further studies showed that fruit from this seedling are considerably larger than normal, although all other fruit characteristics (including polyembryony) were similar to those of standard `Gomera-1' (G-1) fruit. The progeny of this plant has, to date, proved to be morphologically identical to the mother plant. Studies of seedlings from normal G-1 trees growing in the same orchard showed that 10% of the plants had morphological characteristics similar to those of the putative polyploid seedling. Flow cytometry and chromosome count analyses confirmed that G-1 is diploid, whereas the putative polyploid is a stable tetraploid. The study also showed that the morphologically abnormal seedlings from diploid parent trees were spontaneous tetraploids.

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Steven J. Guldan, Charles A. Martin, Jose Cueto-Wong and Robert L. Steiner

Five legumes [hairy vetch (Vicia villosa Roth.), barrel medic (Medicago truncatula Gaerth.), alfalfa (Medicago sativa L.), black lentil (Lens culinaris Medik.), and red clover (Trifolium pratense L.)] were interseeded into sweet corn (Zea mays L.) at last cultivation when sweet corn was at about the V9 (early) or blister (late) stage. The effect of legume interseeding on sweet corn yield, and late-season dry-matter and N yields of aboveground portions of the legumes was determined. Sweet corn yield was not affected by legume interseeding. In 1993, legume dry-matter yields were 1420 kg·ha–1 interseeded early and 852 kg·ha–1 interseeded late. Nitrogen yields were 49 kg·ha–1 interseeded early and 33 kg·ha–1 interseeded late. In 1994, dry-matter yields were 2760 kg·ha–1 interseeded early and 1600 kg·ha–1 interseeded late. Nitrogen yields were 83 kg·ha–1 interseeded early and 50 kg·ha–1 interseeded late. In 1993, barrel medic was the highest-yielding legume with dry matter at 2420 kg·ha–1 and N at 72 kg·ha–1 interseeded early, while red clover yielded the lowest with dry matter at 340 kg·ha–1 and N at 12 kg·ha–1 interseeded late. In 1994, dry-matter and N yields ranged from 4500 and 131 kg·ha–1, respectively, for early interseeded barrel medic to 594 kg·ha–1 and 16 kg·ha–1, respectively, for late interseeded red clover.

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Steven J. Guldan, Charles A. Martin, Jose Cueto-Wong and Robert L. Steiner

Three legumes [hairy vetch (Vicia villosa Roth.), barrel medic (Medicago truncatula Gaerth.), and black lentil (Lens culinaris Medik.)] were interseeded into `New Mexico 6-4' chile pepper (Capsicum annuum L.) when plants were 20–30 cm tall (3 Aug., “early” interseeding) or when plants were 30–40 cm tall (16–17 Aug., “late” interseeding) in 1993 and 1994. Our objectives were to determine the effect of legume interseeding on cumulative chile yield, and late-season dry-matter and nitrogen yields of aboveground portions of the legumes. Legumes were harvested on 8 Nov. 1993 and 15 Nov. 1994. Chile yield was not significantly affected by legume interseeding. In 1993, legumes accumulated 57% more dry matter and 55% more N when interseeded 3 Aug. vs. 16 Aug. In 1994, legumes accumulated 91% more dry matter and 86% more N when interseeded 3 Aug. vs. 17 Aug. Aboveground dry-matter yields in 1993 ranged from 1350 kg·ha–1 for black lentil interseeded late to 3370 kg·ha–1 for hairy vetch interseeded early. Nitrogen yields ranged from 52 kg·ha–1 for black lentil interseeded late to 136 kg·ha–1 for hairy vetch interseeded early. In 1994, hairy vetch was the highest yielding legume with dry matter at 1810 kg·ha–1 and N at 56 kg·ha–1 interseeded early, while black lentil yielded the lowest with dry matter at 504 kg·ha–1 and N at 17 kg·ha–1 interseeded late. In the spring following each interseeding year, we observed that hairy vetch had overwintered well, whereas barrel medic and black lentil had not, except when a few plants of barrel medic survived the winter of 1994–95. Results from this study indicate that legumes can be successfully interseeded into chile in the high-desert region of the southwestern United States without a significant decrease in chile yield.

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Jane M. Marita, José Luis Pires, W. Martin Aitken and James Nienhuis

An increased need to understand the genetic relationships among cacao (Theobroma cacao) germplasm exists to identify cultivars that possess resistance to witches' broom disease (caused by Crinipellis perniciosa). Loss of production due to witches' broom disease in important cacao-growing areas, such as Bahia, Brazil, has generated a strong demand for disease-resistant varieties. Varieties based on single sources of resistance have been released; however, other genotypes are needed to enlarge the genetic diversity of cultivars in breeding programs. A core collection has been created to represent the range of genetic diversity available among the more than 600 cacao accessions at Centro de Pesquisa do Cacau (CEPEC). The cacao core facilitates access to the collection and is intended to enhance its use. This core collection was created from RAPD marker-based estimates of genetic distance among a subset of 270 accessions from the entire collection. The subset was sampled based on 1) witches' broom disease resistance data, 2) random sampling of the collection, and 3) random sampling of recently acquired accessions. Differences in RAPD marker frequencies were used to identify accessions in a witches' broom disease breeding program that contribute to the genetic diversity of the collection as a whole. In addition, differences in RAPD marker frequency allowed the comparison between accessions in the original collection and those acquired from new geographic regions that may expand the collection's genetic diversity.

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Steven J. Guldan, Charles A. Martin, William C. Lindemann, Jose Cueto-Wong and Robert L. Steiner

Hairy vetch (Vicia villosa Roth.), barrel medic (Medicago truncatula Gaerth.), and black lentil (Lens culinaris Medik.) were interseeded into `New Mexico 6-4' chile pepper (Capsicum annuum L.) when plants were 8 to 12 inches tall or 12 to 16 inches tall in 1993 and 1994. Hairy vetch overwintered well both years, whereas barrel medic and black lentil did not. Spring aboveground dry mass yields of hairy vetch averaged 2.11 and 2.57 tons per acre in 1994 and 1995, respectively, while N accumulation averaged 138 and 145 pounds per acre in 1994 and 1995, respectively. Forage sorghum [Sorghum bicolor (L.) Moench] dry mass yield and N accumulation were significantly higher following hairy vetch than following the other legumes or no-legume control. There was no significant difference between forage sorghum yields following barrel medic, black lentil, or the no-legume control. Fertilizer replacement values (FRV) for the legumes were calculated from regression equations for forage sorghum dry mass yield as a function of N fertilizer rate. FRV for hairy vetch were at least 7-times higher than for either barrel medic or black lentil. Hairy vetch interseeded into chile pepper and managed as a winter annual can significantly increase the yield of a following crop compared to a nonfertilized control.

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Raúl De la Rosa, Angjelina Belaj, Antonio Muñoz-Mérida, Oswaldo Trelles, Inmaculada Ortíz-Martín, Juan José González-Plaza, Victoriano Valpuesta and Carmen R. Beuzón

In the present work, a set of eight new hexa-nucleotide simple sequence repeats (SSRs) is reported in olive (Olea europaea L). These SSRs loci were generated on the basis of expressed sequence tag (EST) sequences in the frame of an olive genomic project. The markers showed a high level of polymorphism when tested on a set of cultivars used as genitors in the olive breeding program of Córdoba, Spain. The long-core repeat motif of these markers allows a wider separation among alleles, thus permitting an accurate genotyping. Besides, these markers showed comparable levels of polymorphism to di-nucleotide SSRs, the only ones so far reported in olive. Selected on the basis of their discrimination capacity, four of the eight SSRs were used to test their ability for paternity testing in a total of 81 seedlings coming from 12 crosses. The paternity testing showed that seven crosses matched the alleged paternity and the remaining five were products of illicit pollinations. These results exactly matched with previous paternity testing performed with di-nucleotide SSR markers. These results demonstrate the usefulness of the developed hexa-nucleotide repeated motifs for checking the paternity of breeding progenies and suggest their use on variability studies.