Survey of the Bru1 gene for brown rust resistance in Brazilian local and basic sugarcane germplasm

Bru1 is currently the major gene conferring brown rust resistance in sugarcane, and diagnostic markers are available. A survey for the presence of this gene was conducted on 391 genotypes including Brazilian cultivars, clones and basic germplasm. The efficiency of these markers for identifying resistant cultivars and artificially inoculated basic germplasm was also evaluated. The Bru1 frequency among cultivars (73.5%) suggests this gene is the prevalent source of brown rust resistance in Brazilian sugarcane breeding programmes. Most of the cultivars known to be resistant were positive for Bru1, although other genes for resistance could be present in lines not having Bru1. Only 17.8% of the basic germplasm accessions were positive for the Bru1 gene, and a low correlation between Bru1 diagnostic markers and brown rust severity was observed for basic germplasm accessions. Overall, Bru1 diagnostic markers proved to be efficient identifying resistant cultivars and clones and have potential to be in screening brown rust resistance in Brazilian breeding programmes.     

Pollination and in vitro germination of seeds for interspecific hybridization of <Emphasis Type="Italic">Psidium guajava</Emphasis> and <Emphasis Type="Italic">Psidium cattleianum</Emphasis>

The genus Psidium includes important fruit crops. However, there are very few studies focusing on its reproductive biology, which limits the establishment of breeding programs. The present work investigated the reproductive biology of Psidium guajava and Psidium cattleianum in terms of compatibility of crossings between these two species aiming at interspecific hybridization because the latter species is an important source of resistance against the nematode Meloidogyne enterolobii. Several types of crosses were performed to understand the reproductive biology of these species, including the compatibility of intra- and interspecific crossings, using assisted in vivo germination of pollen grains on the stigma. In addition, the in vitro germination of both Psidium species was studied at different stages of fruit development to rescue young seeds to improve the chances of obtaining the hybrids. No fruits of 270 pollinations were obtained on guava buds at the pre-anthesis stage, regardless of the source of the pollen grain and the cultivar used as female genotype. Microscopic analyzes demonstrated the germination of pollen grains and pollen tube growth at crosses between guava cv. ‘Pedro Sato’ (P. guajava) and Psidium cattleianum. High germination percentages of Psidium cattleianum seeds were obtained in MS medium without sucrose or containing 15 g/L of this carbohydrate.     

Potential environmental and economic impacts of turfgrass in Albuquerque,New Mexico (USA)

We estimated the ecological and economic impact of urban turfgrass production in a large city. A satellite image was used to evaluate the turfgrass area of Albuquerque, New Mexico, U.S.A. Turfgrass, the major vegetation component of the city, covers 7,650 ha and represents approximately 30.0% of the metropolitan area. Of the total grass area, 85.0% exists as home lawns, 8.3% occurs in parks, and 6.7% is on golf courses.We estimated that turfgrass uses an average of 475,000 m³ of water every day, yielding more than 4,575,000 kg of grass clippings going to the landfill in approximately 250,000 garbage bags each year. The approximate yearly cost of maintenance comes to more than $30 million which includes the potential purchase of 322,065 kg of nitrogen fertilizer, 286,110 kg of phosphorus fertilizer, 237,915 kg of potassium fertilizer and 37,408 kg of active ingredients of insecticides.Our evaluation of the cumulative effects of domestic and municipal turfgrass production can guide the application of economically sound Integrated Pest Management strategies and enable planning for sustained use of potentially limiting resources, such as water, in semiarid environments.     

Energy Balance of Callinectes rathbunae Contreras 1930 in Floating Cages in a Tropical Coastal Lagoon

The genus Callinecres is ecologically important in the coastal lagoon region of the Gulf of Mexico. This study was conducted to test the feasibility of raising these crabs in a system of floating cages and to measure their scope for growth in a tropical coastal lagoon of the Gulf of Mexico. The equation P = As - (R + E + N) was used to estimate the scope for growth (P) for C. rathbunae under experimental conditions for 21 days. Ingested food was 3% of body weight. Assimilation (As) was 73% of assimilated energy, 21.4% was channeled to respiration (R), 2% to excretion (N) and 0.16% to exuvia (E). The remainder of the energy was channeled to growth at a net efficiency of 76%. Significant differences were not found between the calculated scope for growth and the growth achieved in the culture system ( P > 0.05). These results support the energy balance equation and suggest that the cultivation of C. rathbunae in floating cages is possible.     

Effect of protein quality on energy requirements for maintenance in growing rats

Forty 3-week old male Wistar rats (initial weight 45-50 g) were used. After weaning they were fed ad libitum for four weeks (I to IV) on 6 isocaloric and isonitrogenous semisynthetic diets based on soya bean meal (diet SBM) or on ground lupin seed (diet LS) alone or autoclaved (A) or not at 120 degrees C and supplemented with DL-methionine (diets ALSm or LSm, respectively) or with DL-methionine + L-lysine (diets ALSm + l or LSm + l). The diets differ in their protein quality and were formulated in order to provide the adequate experimental conditions to determine the biological value (10% crude protein). Then over the fifth and sixth weeks (V and VI) the rats were fed on the same diets but restricted to 60% of the voluntary feed intake. In a parallel experiment, a group of eight rats previously fed ad libitum on diet SBM for four weeks was fasted for 72 h and then fed on the same diet at a level of intake slightly below maintenance. After a 24 h adaptation period, irrespective of the level of intake and type of diet, a series of 24 h gas-exchanges measurements were carried out in open-circuit respiration chambers. Measurements of energy balance were used to calculate ME for maintenance (MEm) and the efficiency of utilization of ME, using a linear regression of energy retention (RE) on ME. The estimates for MEm derived from energy balances of rats fed above maintenance ranged from 564 to 621 kJ/kgW0.75 per d. No significant differences between diets were observed. From pooled data MEm was found to be 599 kJ/kgW0.75 per d, a value not significantly different from that calculated from measurements at fasting and below maintenance levels (598 kJ/kgW0.75 per d). The efficiency of utilization of ME for maintenance was 81.1% and the efficiencies of utilization of ME for RE ranged from 36.6 to 59.9%. It is concluded that no variations in MEm requirements in growing rats attributable to variations in dietary protein quality have been found. Nevertheless, these results should be taken with caution because of limitations inherent of statistical modelling approaches of partitioning ME.     

Experimental Collection of Pearl Oyster, Pinctada mazatlanica and Pteria sterna, Spat on a Filament Substrate

Juveniles of Pinctada mazatlanica and Pteria sterna were collected with artificial collectors from Falsa Bay, Baja California Sur, Mexico during a 12 month experimental period. Filament substrate artificial collectors contained in 2 mm plastic mesh bags (25 ± 25 cm) were deployed from the surface to 17 m of depth, and replaced monthly. Pinctada mazatlanica had the greatest recruitment (12 juveniles/cm²) in late summer and P. sterna (5 juveniles/cm²) in winter. Maximum spat collection from September 1986 to April 1987 occurred at 10 m depth for P. mazatlanica and at 4–7 m depth for P. sterna . However, peak spatfall under 11m depth occurred from late July to August 1987. The mean prodissoconch shell height was 254 μ m (SE = 0.003; N = 50) for P. mazatlanica and 313 μm (SE = 0.004; N = 50) for P. sterna . The growth equations for the first five weeks of both species, based on the prodissoconch shell height and the maximum spat height (measured from the umbo to distal edge) are presented.     

Fungal endophyte diversity in Paspalum and effects on plant growth

In natural ecosystems, plants appear to be in symbiosis with diverse fungal endophytes which can have impacts on plant communities. Paspalum is one of the most important grass genera in South American grasslands. The aim of this work was to determine the presence of fungal endophytes in two Paspalum species and evaluate their effects on plant growth. Sixty plant samples were collected for Paspalum notatum in a rangeland in northeastern Argentina, and the same number for Paspalum dilatatum in central Argentina. A triple-sterilization process was carried out by submerging small pieces of leaves and stems for the isolation of fungi from the collected plants. In order to identify endophytes, morphological characters and fungal sequences corresponding to the ITS (Internal Transcribed Spacer) region were analysed. A total of eight genera were identified: Acremonium, Alternaria, Aspergillus, Bipolaris, Cladosporium, Fusarium, Penicillium and Trichoderma. A greenhouse trial was conducted to determine the effects of fungal endophytes on growth. Trichoderma significantly increased relative chlorophyll content in P. notatum and Acremonium endophytes increased tiller number, and above- and below-ground biomass in P. dilatatum. The diversity of fungal endophytes that was present in P. notatum and P. dilatatum was described. In conclusion, some aspects of growth of these Paspalum species seem to be positively affected by Trichoderma and Acremonium.     

Susceptibility of cork oak (Quercus suber) to canker disease caused by Diplodia corticola: when time is of the essence

New Forests - Cork is a renewable resource mainly produced in Mediterranean countries thanks to sustainable management of cork oak (Quercus suber) stands. The infection caused by the ascomycete...