Nature of 'Pollinator' Effect in Potato (Solanum tuberosum L.) Haploid Production

Haploids (2n =24) of the common tetraploid (2n=48) potato (SolanumtuberosumL.) provide promising material for attacking many problemsconcerned with the genetics, cytogenetics and breeding of thisspecies. Interspecific 4xx2xcrosses betweenSolanum tuberosumgp.Andigenaorgp.Tuberosumcultivars as pistillate parents andSolanum tuberosumgp.Phurejaassource of pollen (hereafter ‘pollinator’) have beenused to produce maternally derived haploids through parthenogenesis.This paper discusses the nature of the ‘pollinator’effect in haploid extraction. The ‘pollinator’ hada significant effect on haploid frequencies following 4xx2xcrosses.The ‘pollinator’ effect seems to operate via theendosperm, in which haploid (n=2x) embryos are associated withhexaploid endosperm. A superior ‘pollinator’ appearsto have its effect by contributing two haploid (n) gametes tothe central cell. 2n pollen; double fertilization; endosperm; ploidy manipulations; Solanum tuberosum     

Distribution and incidence of yellowing viruses in sugar beet crops in Spain from 1990 to 1993

Surveys of the principal yellowing viruses of sugar beet, beet yellows virus (BYV) and beet mild yellowing virus (BMYV) in Spain were carried out from 1990–1993. Beet yellowing viruses were detected in all provinces, although the mean percentages of plants infected with BYV and BMYV were practically zero in the southern zone. Within the northern zone high variations from one province to another could be observed. The mean percentages of plants infected with BYV were higher in the Ebro Valley than in the Duero Valley. Areas infected with BYV were very restricted, while BMYV could be found to a variable extent all over Spain, although the infection levels were lower. The incidence and distribution of these viruses in the Spanish sugar beet crop makes the study and application of control measures for beet yellowing viruses necessary.     

Discrimination Amongst Leishmania by Polymerase Chain Reaction and Hybridization with Small Subunit Ribosomal DNA Derived Oligonucleotides

ABSTRACT. A method for discriminating among Leishmania is described, based upon small subunit ribosomal DNA sequence differences. The method was to amplify the entire 2.2 kb small subunit rDNA by polymerase chain reaction using conserved primers specific for the 5' and 3' termini of the small subunit ribosomal RNA, and then hybridize the product dotted onto nylon membranes with labeled oligonucleotides. The design of the hybridization probes was based upon complete small subunit rDNA sequences from L. amazonensis, L. major and L. guyanensis and partial sequences of L. mexicana, L. braziliensis, L. tropica and L. chagasi. A high degree of sequence similarity (> 99%) among species was found. However, sufficient sequence divergence occurred to permit the design of internal oligonucleotide probes specific for species complexes. This procedure successfully discriminated amongst a wide range of Leishmania isolates. The method detected as few as 10 cultured organisms and detected parasites in tissue samples from experimentally infected animals. Non-radioactive labeling showed the same specificity and sensitivity as radioactive probes.     

Cybrids and tetrad sterility for developing true potato seed hybrids

Potato cybrids result from the fusion between cytoplasm and nuclear gene donors. Such genetic materials are an alternative means to broaden the breeding pool by non‐sexual gene transfer. Tetrad pollen sterility provides also another source of male sterility with some potential for true potato seed breeding. The objective of this research was to investigate cybrid‐derived offspring for both agronomic and reproductive characteristics in two contrasting Peruvian locations, and to examine new exotic germplasm for tetrad sterility, with the aim of broadening the breeding pool available at the Centro Internacional de la Papa (CIP). The cybrids were derived from fusions between Y‐245.7, a clone with tetrad sterility, and Atzimba. These cybrids were crossed with selected male parents from the CIP breeding population, and their hybrid offspring were tested in La Molina (coastal desert) and Huancayo (cool highlands). In addition, other clones with tetrad sterility were also crossed with selected testers to determine their breeding value. There were significant differences for tuber yield, style length, and berry number among the hybrid offspring, and the genotype by environment interaction was significant for tuber yield and berry number. The top 25% highest yielding cybrid‐derived offspring across both locations showed the same tuber yield although they were significantly different for some of the reproductive characteristics. With the exception of one cybrid, the others did not exhibit segregation for tetrad sterility in their hybrid offspring, which were male fertile. However, the offspring derived from crosses between other sources of tetrad sterility and the same testers all showed tetrad sterility, and some of them had outstanding tuber yield at La Molina. The lack of segregation for tetrad sterility in these new crosses suggests that the non‐cybrid, male sterile, female parents are triplex or quadriplex for the Tr nuclear locus, which interacts with a sensitive cytoplasm (e.g. Trs from S. verrucosum or S. stoloniferum) to produce tetrad sterility in potato.     

Edge Effect on Density Estimates of a Radiotracked Population of Yellow-Necked Mice

ABSTRACT Density estimates for small-mammal populations from capture-mark-recapture (CMR) data have played an important role in many studies of theoretical and applied ecology. Defining effective trapping area (ETA) is one of the main issues affecting accuracy of density estimates. Our objective was to assess sensitivity of CMR density estimates to correctors based on movement parameters calculated from trapping and radiotelemetry data. From May to November 2005, we conducted monthly CMR trapping in a beech (Fagus sylvaticus) forest of the province of Trento, northern Italy. In conjunction with CMR, we radio-marked 32 yellow-necked mice (Apodemus flavicollis) captured from July to October and located them daily using radiotelemetry. We estimated population size (N) by model averaging with Program MARK. We calculated ETA using several definitions of the boundary strip, including full and half mean maximum distance moved (MMDM) from capture-recapture and telemetry data and mean radius of mean monthly home ranges. The boundary strip (W) increased with the amount of behavioral information embodied in the estimates. The largest W and lowest density values were based on radius of mean home ranges followed by MMDM calculated from telemetry data. The ETA based on movement distances increased more than proportionally when N decreased, suggesting that low population density combined with scarce resources results in rodents moving more in search of food, thus leading to overestimated ETA and underestimated density values. Although robust behavioral information would certainly improve density estimates, we suggest caution in relating ranging movements to capture probability and hence in using correctors based on movement distances to infer density values.     

In Vitro Cultivation of the Vascular Phase of Sarcocystis singaporensis

To establish an in vitro culture system for the precystic phase of Sarcocystis singaporensis, we initially tested various excysting fluids for sporocysts. An excysting fluid containing 2.5% bovine taurocholate and 10% bile of the specific intermediate host, Rattus norvegicus, in RPMI medium was the most suitable resulting in excystation of 80% of the sporozoites. Subsequently, we identified brain endothelial cells and pneumonocytes of the rat to promote growth of sporozoites to schizonts. Hepatoma, fibroblastic, or myoblastic cells were not suitable for the parasite's development. First-generation schizonts were seen at days 3-10 postinoculation (PI); a distinct second peak of schizogonic development only occurred in endothelial cells at days 14-18 PI. First-generation schizonts were 26.0 (± 3.8) μm in diameter and contained 32-50 merozoites, second-generation schizonts measured 34.4 (± 10.6) μm and contained 54-72 merozoites. Merozoite yield at large-scale culture conditions (75 cm² flasks) using pneumonocytes as host cells was relatively low. Ultrastructurally, sporozoites and merozoites were quite similar to corresponding stages of other Sarcocystis species. With regard to host cell specificity and developmental kinetics, in vitro cultivation showed close similarities to the situation in vivo.     

Ultrastructure of Enteromyxum leei (Diamant, Lom, & Dyková, 1994) (Myxozoa), an Enteric Parasite Infecting Gilthead Sea Bream (Sparus aurata) and Sharpsnout Sea Bream (Diplodus puntazzo)

ABSTRACT. The ultrastructure of the developmental stages of the myxozoan Enteromyxum leei parasitizing gilthead seabream ( Sparus aurata ) intestine and sharpsnout sea bream ( Diplodus puntazzo ) intestine and gallbladder are described. The earliest stage observed was a small dense trophozoite located among enterocytes. Proliferative stages, observed intercellularly in the epithelium of the intestine and gallbladder as well as in the lumen, possessed the typical cell-in-cell configuration throughout their development. Secondary cells were seen undergoing division within a common vacuolar membrane that also encompassed pairs of tertiary cells. Cytochemical studies showed that primary cells stored mainly lipids whereas secondary cells stored abundant β-glycogen granules. Sporogonic development resembled that described for other disporous myxozoans. Within sporogonic stages, nonsporogonic secondary cells were observed accompanying two developing spores. Mature spores had a binucleated sporoplasm in which glycogen stores were abundant and no sporoplasmosomes were found. Our observations are discussed in relation to our knowledge on other myxozoans of the genus Enteromyxum .     

Anatomy of extrafloral nectaries in Fabaceae from dry‐seasonal forest in Brazil

Extrafloral nectaries (EFNs) are found in many species of Fabaceae. The aim of this work is to describe the internal morphology of the EFNs from species of Fabaceae found in areas of dry‐seasonal forest in north‐eastern Brazil. All species of Fabaceae with EFNs found were collected and samples were submitted to conventional techniques for anatomical and scanning electronic microscopy analysis. EFNs were found in 35 species, of which 32 were examined anatomically. All types have epidermal cells, secretory tissues and vascular bundles in the EFNs. Sclerenchymatous cells were found between the secretory tissues and the vascular tissues, with a few exceptions. The function of these cells is not clear; however, a role in the transportation of the sap in the nectary or with the support of the secretory tissue is possible. The nectar is released through glandular trichomes, secretory pores or even by breaking the epidermal cells and cuticle. The internal patterns found in the EFNs from different species and genera can provide important information for taxonomic and evolutionary studies in the family. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 163 , 87–98.