Genetic diversity among watermelon (Citrullus lanatus and Citrullus colocynthis) accessions

Genetic diversity was estimated among 42 U.S. PlantIntroduction (PI) accessions of the genusCitrullus (of these, 34 PIs are reported tohave disease resistance), and 5 watermelon cultivars, using 30RAPD primers. These primers produced 662 RAPD markers that could berated with high confidence. Based on these markers, geneticsimilarity coefficients were calculated and a dendrogram wasconstructed using the unweighted pair-group method witharithmetic average (UPGMA). The analysis delineated threemajor clusters. The first cluster consisted of a group of fivewatermelon cultivars, a group of C.lanatus var. lanatusaccessions, and a group of C.lanatus var. lanatusaccessions that contained some C.lanatus var. citroidesgenes. The second cluster consisted of the C.lanatus var. citroidesaccessions, while the third cluster consisted of theC. colocynthis accessions.The two C. lanatus clustersdifferentiated from each other and from the C.colocynthis cluster at the level of 58.8%and 38.9% genetic similarity, respectively. Assessment ofgenetic diversity among accessions that have been reported to havedisease resistance indicated that resistance to either anthracnose,downy mildew, powdery mildew, or watermelon mosaic virus is foundamong all major groups of Citrullus PIs.Additionally, resistance to gummy stem blight or Fusarium wilt mayexist among C. lanatus var.citroides PIs. This study demonstrates thatmolecular markers can be useful in assessing genetic diversity, andin sorting Citrullus PIs into phylogeneticgroups prior to their evaluation for disease or pestresistance.     

Endomycorrhizae in a newly cultivated acidic meadow: Effects of three years of barley cropping,tillage, lime,and phosphorus on root colonization and soil infectivity

The dynamics of mycorrhizae under disturbance created by crop production is not well understood. A 3-year experiment was undertaken on a nutrient-poor and acidic land that had last been cultivated in the early 1970s. We observed the effects of cropping spring barley (Hordeum vulgare L.) under four P-fertilizer levels and four levels of lime, in a minimum (rototillage), a reduced (chisel), or a conventional tillage system, on the mycorrhizal receptiveness of the host (maximum level of mycorrhizal colonization, as measured at harvest) and soil infectivity most probable number method. The host receptiveness decreased with time, while crop yields and soil infectivity increased simultaneously with time. Liming increased mycorrhizal colonization of barley roots and soil infectivity. P additions decreased root colonization but did not significantly affect the most probable number valuse. Slightly higher soil infectivity estimates were found under reduced tillage.     

Analysis based on RAPD and ISSR Markers Reveals Closer Similarities among <Emphasis Type="Italic">Citrullus</Emphasis> and <Emphasis Type="Italic"> Cucumis</Emphasis> Species than with <Emphasis Type="Italic">Praecitrullus fistulosus</Emphasis> (Stocks) Pangalo

A cucurbit species named Praecitrullus fistulosus (Stocks) Pangalo, which thrives in India, is considered to be a distant relative of watermelon. Recent experiments indicated that it has mild resistance to whiteflies (Bemisia tabaci). However, our attempts to cross various US plant introductions (PIs) of P. fistulosus with watermelon or other Citrullus PIs have not been successful. Thus, to determine genetic relatedness among those species, phylogenetic analysis [based on simple sequence repeat (SSR)–anchored (also termed ISSR), and randomly amplified polymorphic DNA (RAPD) markers] was conducted among PIs of P. fistulosus, Citrullus lanatus var. lanatus (watermelon), C. lanatus var. citroides and the wild Citrullus colocynthis. Phylogenetic relationships were also examined with Cucumis melo (melon), Cucumis sativus (cucumber), and wild Cucumis species including C. africanus, C. metuliferus, C. anguria, C. meeusei, and C. zeyheri. Wide genetic distance exists between Citrullus and Cucumis groups (8% genetic similarity). Phylogenetic relationships among Citrullus species and subspecies are closer (25–55% genetic similarity) as compared with those among most Cucumis species (14–68% genetic similarity). P. fistulosus appeared to be distant from both Cucumis and Citrullus species (genetic similarity between P. fistulosus and Cucumis or Citrullus groups is less than 3%). Although wide genetic differences and reproductive barriers exist among cucurbit species examined in this study, they are still considered as potential germplasm source for enhancing watermelon and melon crops using traditional breeding and biotechnology procedures.     

Sediment Quality in Arkansas Bait Minnow Ponds

Sediment cores were collected from 7-yr-old, 20- to 25-yr-old, and 30- to 35-yr-old ponds at a bait minnow farm at Lonoke, Arkansas, USA. Average depths of soft sediment (S and M horizons) were 8 cm in young ponds, 12 em in intermediate-age ponds, and 26 cm in old ponds. Organic carbon concentrations in sediment were low to moderate (1–2%) and carbon to nitrogen ratios were wide (20–50). Phosphorus and sulfur concentrations increased as ponds aged. Most of the phosphorus (78.9%) was in organic form, but sulfur was primarily inorganic in form (presumably iron sulfide). There appears to be two major problems associated with sediment accumulation over time. Deep, soft sediment interferes with pond management and especially with harvest. High phosphorus concentration in old sediment may contribute to dense phytoplankton blooms by supplying phosphorus to the water. Sodium nitrate treatment did not increase the rate of sediment organic matter decomposition in laboratory trials and would not be expected to enhance the degradation of sediment organic matter in ponds. The best method for improving the condition of bottoms in older bait minnow ponds probably is to remove the sediment.     

Dry-Tilling of Pond Bottoms and Calcium Sulfate Treatment for Water Quality Improvement

Three different pond bottom treatments were evaluated in 12 earthen ponds. Bottoms of four ponds on the Auburn University Fisheries Research Unit, Auburn, Alabama, were dried for 1 mo and tilled with a roto-tiller (dry-till treatment). Four other ponds were dried and tilled, and after filling with water, enough gypsum (calcium sulfate) was applied to give a total hardness of about 200 mg/L. Gypsum was reapplied as needed to maintain the hardness (dry-till with gypsum treatment). Four ponds were not subjected to bottom drying, tilling or gypsum treatment (controls). Channel catfish Ictalurus punctatus fingerings were stocked at 15,000/ha. Selected water quality variables were measured at 1- to 2-wk intervals during the growing season. Concentrations of most variables increased over time because feeding rate was increased progressively as fish grew. Compared to the controls, both treatments had lower concentrations of total phosphorus and soluble reactive phosphorus, and higher concentrations of dissolved oxygen ( P < 0.05). In addition, ponds of the dry-till with gypsum treatment had in addition lower concentrations ( P < 0.05) of chlorophyll a , chemical oxygen demand, gross primary productivity, and total alkalinity than control ponds. The reduction in chlorophyll a concentration suggested less phytoplankton in gypsum-treated ponds, and this effect was probably related to lower phosphorus availability because of calcium phosphate formation. Secchi disk visibility, total suspended solids concentrations, and turbidity did not differ significantly among the treatments ( P < 0.05). Total fish production and survival rate did not differ significantly ( P < 0.05) among the treatments. These findings suggest that water quality improvement can be achieved by drying and tilling pond bottoms between crops, and benefits possibly may be increased by treating low hardness waters with gypsum.     

Somatostatin receptor imaging in vivo by planar scintigraphy facilitates the diagnosis of canine insulinomas

Somatostatin receptors expressed by insulinomas in 5 dogs were imaged in vivo by means of indium in 111 pentetreotide (OctreoScan) scintigraphy. The diagnosis in each dog was supported by the presence of hypoglycemia (<60 mg/dL), hyperinsulinemia (>20 microU/mL), and histopathologic review of neoplastic tissue. All insulinomas expressed high-affinity somatostatin receptors of subtype sst2, as shown by receptor autoradiography in vitro using 125I-[tyrosine3]-octreotide and 125I-[leucine8, Dtryptophan22, tyrosine25]-somatostatin-28 with an sst2 subtype-selective analogue. Scintigrams were obtained at 1, 4, 12, and 24 hours after the i.v. administration of 74-222 MBq of OctreoScan to each patient. Abnormal foci of activity were 1st observed from 1 hour after administration of the radioligand in dog 3, to 24 hours after its administration in dog 4; in dogs 1 and 2, abnormal foci of activity were visible from 12 hours. Dog 5 showed a questionable abnormal focus of activity at 12 hours, but not at 24 hours. Scintigraphy enabled accurate prediction of the anatomical location of the primary tumor in 1 of 4 dogs, but was unable to differentiate a right- from a left-pancreatic lobe tumor, or vice versa, in 3 dogs; the 5th dog had equivocal results. 111In-pentetreotide scintigraphy is a useful diagnostic adjunct to the clinical evaluation of the insulinoma patient, but is unable to localize the tumor in some cases.     

Cutaneous metastases of a bronchial adenocarcinoma in a cat

This case report describes a cat with metastasis of a bronchial adenocarcinoma to the abdominal skin. The cat had been treated with antibiotics and corticosteroids for several episodes of coughing when it acutely developed erythema, pustules and plaques on the abdominal skin. Diagnosis was based on cytological examination of fine-needle aspirates of cutaneous pustules, X-ray examination of the thorax and histological examination of skin biopsy samples. As the prognosis was poor, the cat was euthanased. Necropsy findings confirmed the diagnosis. Cutaneous metastases of lung carcinoma are rare in cats but have been reported in the digits with underlying bone involvement. To the authors' knowledge, this is the first report of metastasis of a feline bronchial carcinoma to the ventral skin.     

Comparison of three methods for arthrodesis of the distal intertarsal and tarsometatarsal joints in horses

OBJECTIVE: To evaluate the effects of diode laser surgery (LS), surgical drilling (SD), and intraarticular sodium monoiodoacetate (MIA) as methods for fusing the distal intertarsal (DIT) and tarsometatarsal (TMT) joints in horses. STUDY DESIGN: Experimental study. ANIMALS: Adult horses (15) without radiographic signs of osteoarthritis (OA) of the DIT and TMT joints. METHODS: Group 1 (n=3) had LS performed bilaterally on DIT and TMT joints; 1 horse was evaluated for 1 week and 2 horses were evaluated for 2 weeks. Group 2 (n=6) had LS on DIT and TMT joints of 1 tarsus and MIA administration into the contralateral DIT and TMT joints and were evaluated for 6 months. Group 3 (n=6) had LS performed on DIT and TMT joints of 1 tarsus and SD of the contralateral DIT and TMT joints and were evaluated for 12 months. Postoperative comfort, lameness, radiography, microradiography, and histology scores were compared using repeated measures ANOVA, and paired or 2 sample t-tests; significance was set at P<.05. RESULTS: LS caused the least postoperative morbidity. In group 2, horses were less lame in 4 LS-treated limbs and 2 MIA-treated limbs at 6 months when compared with the contralateral limb. In group 3, horses were less lame in 5 LS-treated limbs and 1 SD-treated limb at 6 and 12 months compared with the contralateral limb. On microradiography, 11 MIA joints and 2 LS joints had bone bridging the joint at 6 months whereas 8 SD joints and 5 LS joints had bone bridging at 12 months. Significantly more joint space was bridged by bone in MIA- (51.4%) and SD (46.2%)-treated joints compared with LS joints at 6 (30.6%) and 12 (28.5%) months, respectively (P<.05). CLINICAL RELEVANCE: SD and MIA resulted in more bone bridging of the distal 2 tarsal joints, than LS. However, LS seemingly caused less pain and discomfort to horses in the immediate postoperative period; horses were generally less lame in the LS limb. More laser energy may need to be applied to these joints to promote fusion; however, it may also have beneficial effects beyond fusion. Further research on horses with OA of the distal 2 tarsal joints is needed to determine whether LS can cause soundness without facilitating bony fusion.