Effect of root temperature on nodule development of bean, lentil and pea

The rhizobia-legume symbiosis is the main source of fixed nitrogen for many agricultural systems. However, it is inhibited by low soil temperature. To date, research on nodulation has involved either qualitative or destructive analyses. The use of computer-based image analysis potentially allows nodules to be followed during the course of development. Seedlings of bean (Phaseolus vulgaris L.), lentil (Lens culinaris Medik.) and pea (Pisum sativum L.) were transplanted into plastic growth pouches suspended in water baths maintained at 10, 15, 20 or 25 °C. Two days after transplanting, all plants were inoculated with appropriate rhizobial strains. Seven days after inoculation, plant roots were scanned; this was repeated weekly for 7 weeks. Data on nodule length were collected through image analysis. Nodule length was correlated with nodule size and development. There were increases in the precision of estimates of environmental effects through observation of individual nodule development, as opposed to averages for populations of nodules. The effects of root temperature on nodulation and nodule development were observed both in the delayed onset of nodulation and in reduced subsequent nodule growth rate, resulting in effects on final nodule size.     

Simple and inexpensive flow L-glutamate determination using pumpkin tissue

This work refers to a very easy to implementate flow injection system with potentiometric detection for l-glutamate determination in food samples. The proposed procedure is based on measurement of carbon dioxide produced by decarboxylation of l-glutamate catalyzed by l-glutamate decarboxylase (E.C. 4.1.1.1.5) from Cucurbita maxima (pumpkin). The FI potentiometric system includes an enzymatic reactor with a length of 8 cm and thickness of 5 mm packed with 200 mg of a C. maxima outer layer cut in to small pieces. The proposed procedure allowed l-glutamate determinations in the concentration interval of 10-100 mmol L(-1) for an injected sample volume of 50 microL. A phosphate buffer (0.1 mol L(-1), pH 5.5) solution flowing at 1.4 mL min(-1) was used as the carrier solution in the system. The results obtained in the analysis of food samples revealed a relative error lower than 5% when compared with those provided by the spectrophometric reference procedure. The immobilized reactor retained its initial activity for 21 days. It was possible to measure 40 samples/h with the flow system proposed.     

A multiplex PCR for the detection of Brucella spp. and Leptospira spp. DNA from aborted bovine fetuses

Bovine brucellosis and leptospirosis are important causes of bovine abortion around the world. Both diseases can be serologically diagnosed, but many factors may cause false positive and negative results. Direct methods based on bacteriological isolation are usually employed, but they are difficult, time consuming and dangerous. Monoplex polymerase chain reaction (PCR) have been successfully described for the detection of Brucella spp. and Leptospira spp. Aiming at improvement in the direct diagnosis, a multiplex PCR (mPCR) for the detection of these agents in aborted bovine fetuses is described. The detection threshold of the mPCR was evaluated in experimentally contaminated bovine clinical samples using a conventional proteinase K/SDS or a boiling-based extraction protocols. The mPCR was applied to two groups of clinical samples: 63 episodes of bovine abortion and eight hamsters experimentally infected with Leptospira interrogans serovar pomona. Adopting microbiological isolation as reference, the test showed a sensitivity of 100% in both groups of clinical samples. Seven samples collected from bovine fetuses were Brucella spp. culture negative but showed positive results in mPCR. Regarding Leptospira spp. detection, similar results were observed in three bovine clinical samples. All hamsters infected with Leptospira were positive in both microbiological culture and mPCR. The boiling extraction protocol showed better results in some clinical samples, probably by the removal of PCR inhibitors by heat treatment. The high sensitivity, simplicity and the possibility of detection of both bacteria in a single tube reaction support the use of the mPCR described in the routine diagnosis.     

Longevity of Mycobacterium bovis in brushtail possum (Trichosurus vulpecula) carcasses,and contact rates between possums and carcasses

Abstract

AIM: To determine, for a variety of environmental conditions, how long Mycobacterium bovis might remain viable inside the carcass of a brushtail possum (Trichosurus vulpecula) that died of bovine tuberculosis (Tb), and to measure the rate of contact between free-ranging possums and possum carcasses.

METHODS: Lesions of M. bovis were simulated by inoculating excised spleens weighing 0.5–1 g with 0.2 mL liquid culture containing approximately 5 x 10⁷ cfu M. bovis/mL. Simulated lesions were inserted into possum carcasses (n=48) at the peripheral lymph nodes. Carcasses were placed in the field at two sites (a tussock grassland and a podocarp-broadleaved forest site) and in two seasons (summer and winter) for up to 62 days. Survival rates of M. bovis were estimated by sampling the simulated lesions over time, and culturing the recovered lesion to determine if any viable M. bovis bacteria were present.

The time taken for a free-ranging possum to first encounter a dead possum in its home range was estimated by live-trapping possums and fitting them with proximity loggers (n=13). A ‘contact’ was recorded if these possums came within 40–50 cm of proximity loggers fitted to possum carcasses.

RESULTS: There were strong seasonal and site effects in the survival rate of M. bovis in possum carcasses. In the grassland habitat, no viable bacilli were cultured from any carcass after 3 days in summer, whereas in winter all samples were culture-positive for the first 20 days, and some were still positive after 27 days. The survival rates for forest habitat were intermediate between the results for grassland, and there were no culture-positive carcasses after 9 days in summer or 27 days in winter.

In summer, infected carcasses (n=6) were first encountered by possums a mean 1.9 (range 0.4–6.7) days after placement.

CONCLUSIONS: Possum carcasses were contacted by free-ranging possums within the period that viable M. bovis were shown to survive in a carcass. The risk of such infection is likely to be most significant in winter or in areas with microhabitats where the survival of M. bovis is high. However, the generally low survival rate of M. bovis in possum carcasses and the low frequency of possum-to-carcass contacts indicate this route of transmission alone could not maintain Tb in a possum population.     

A Case of Successful Pregnancy in a Ewe with Uterus Didelphys

Uterus didelphys is a rare congenital abnormality of the reproductive tract. Although it occurs in various species, there are no published reports describing pregnancy outcome in association with this abnormality. Herein we describe a case of successful unilateral singleton pregnancy in a ewe incidentally found to have uterus didelphys during the course of a biomedical research study. The pregnancy was established using assisted reproductive techniques and interrupted in late gestation, at which point the abnormality was identified. Serial ultrasound assessment of foetal biometry revealed a normal foetal growth trajectory. Despite a 45% reduction in placentome number, total placentome weight was near normal secondary to compensatory placentome growth and development. To our knowledge, this is the first detailed report of normal foetal growth in an animal with uterus didelphys and illustrates the ability of the ovine placenta to adapt to a reduced number of placentomes and maintain foetal nutrient supply.     

Pleistocene collapse of the west antarctic ice sheet

Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B contain Quaternary diatoms and up to 10(8) atoms of beryllium-10 per gram. Other samples contain no Quaternary diatoms and only background levels of beryllium-10 (less than 10(6) atoms per gram). The occurrence of young diatoms and high concentrations of beryllium-10 beneath grounded ice indicates that the Ross Embayment was an open marine environment after a late Pleistocene collapse of the marine ice sheet.     

Activity pattern of the marine shrimp Litopenaeus vannamei (Boone 1931) in laboratory as a function of different feeding frequencies

Management practices on most Brazilian shrimp farms have resulted in high expenses for producers and damage to the environment. Applied ethology could provide information on the pattern of shrimp activity, enabling more efficient feeding frequencies. Behavioural activities of the shrimp Litopenaeus vannamei were recorded during different feeding frequencies. The shrimp were kept in aquariums on a 12:12 h light/dark cycle. They were fed commercial ration three (at 6:00, 12:00 and 18:00 hours), four (at 6:00, 10:00, 14:00 and 18:00 hours) or seven times per day (at 6:00. 8:00, 10:00, 12:00, 14:00, 16:00 and 18:00 hours). We observed animals at 15 min^?1 aquarium^?1 time periods, recording feeding, substrate exploration, swimming and inactivity. Feeding and exploration were the highest for shrimp fed three times per day, swimming was greatest when animals received four feedings, whereas inactivity was higher for shrimp fed seven times per day. There was greater food ingestion between 12:00 and 14:00 hours for animals fed three and four times per day, whereas swimming was high mainly at 18:00 hours for shrimp fed three and seven times per day. The results indicate higher forage‐related activities (exploration/ingestion) when feed was offered three or four times, suggesting optimization in the pattern of shrimp activities based on these feeding frequencies.     

Characterization of the anthracnose resistance gene present in Ouro Negro (Honduras 35) common bean cultivar

Ouro Negro (Honduras 35) is a highly productive Mesoamerican black seeded bean cultivar that possesses a major dominant gene conferring resistance to anthracnose (causal organism Colletotrichum lindemuthianum). In this work the anthracnose resistance gene present in Ouro Negro was characterized by studying allelic relationships to the following previously characterized anthracnose resistance genes (cultivars): Co-1 (MDRK), Co-1 ² (Kaboon), Co-1 ³ (Perry Marrow), Co-2 (Cornell 49-242), Co-3 (Mexico 222), Co-4 (TO), Co-4 ² (SEL 1308), Co-5 (SEL1360), Co-6 (AB 136), and the resistance genes present in PI 207262 and Widusa. In addition, we determined the resistance spectrum of Ouro Negro in relation to 19 pathotypes of C. lindemuthianum. The allelism tests confirmed that the dominant anthracnose resistance gene present in Ouro Negro is positioned at a locus distinct from those with which it was compared. We propose that this new gene be named Co-10. The inoculation of Ouro Negro with the 19 pathotypes of C. lindemuthianum demonstrated that Co-10 confers resistance to pathotypes 23, 64, 67, 73, 81, 83, 87, 89, 95, 102, 117, 119, 343, 453, 1033, 1545 and 1600. The identification of Co-10 is an important contribution to bean breeding programs that are in constant need of new sources of resistance to anthracnose. This revised version was published online in July 2006 with corrections to the Cover Date.     

Economic viability of Phaseolus vulgaris (BRS Estilo) production in irrigated system in a function of application of leaf boron

Foliar fertilization may be a viable strategy to boron supply in irrigated cropping systems with common beans (Phaseolus vulgaris), since it prevent B leaching. The aim of this work was to evaluate the economic viability and physiological parameters of the common beans production in irrigated cropping systems using sources and increasing foliar boron doses. A field experiment was carried out using an experimental block design in a factorial scheme 2?×?5?×?3, with two sources of B (boric acid and borax) and five doses: 0 (control), 2, 4, 6 e 8?kg?ha^?1, with three repetitions. Foliar B applications were performed at 40 days after seeds germination, in pre-flowering stage. Physiological process (transpiration, stomatal conductance, CO₂ internal concentration, net photosynthesis, and relative chlorophyll index), B level in leaves and grain yield were measured. These data were used to determine the economic viability of B fertilization in common beans. Both boric acid and borax increased B levels in common beans leaves. Borax affected some physiological process reducing stomatal conductance and increasing net photosynthesis. Using borax, the highest net photosynthesis was observed at a rate of 4?kg?ha^?1, while the boric acid increased net photosynthesis linearly after increasing B doses application. An enhance of 311?kg?ha^?1 in the grain yield was observed using borax related to the control (without B application); however, grain yield decreased linearly after application of increasing B doses, as boric acid. Comparing the economic viability of sources and doses of B, the highest profitability is obtained using borax at a rate of 4?kg?ha^?1, which promoting a differential profit of US$534.44 per hectare compared to common beans cropping without B.