Monosomic analysis of genes for resistance against stem rust races in bread wheat

Summary Two Abelmoschus species, viz., A. manihot (L.) Medik and A. manihot (L.) Medik ssp. manihot, resistant to Okra yellow vein mosaic (YVM) were crossed to A. esculentus cv. Pusa Sawani, a susceptible culture. The hybrids were resistant and partially fertile. Segregation pattern for disease reaction in F₂, BC₁ and subsequent generations of the two crosses revealed that resistance to YVM is controlled by a single dominant gene in each species.     

Interspecific competition between two species of Trichogrammatidae III The analytical study on the competition

The experiment was carried out in order to analyze the results of interspecific competition which were mentioned in the previous reports (Sasaba 1964, 1965). The following definite tendencies were obtained and an account was given with regard to the process of competition. (1)T. minutum had a higher reproductive rate than T. japonicum at a lower density of the parent wasps. (2) The parasitic efficiency of T. minutum was high as compared with T. japonicum. (3)T. japonicum was consistently superior to T. minutum in the interspecific competition at larval stage.     

Competitive influence of isaza,Chaenogobius isaza,on ayu,Plecoglossus altivelis,in Lake Biwa

1. Competitive influence of the isaza population on the ayu population was studied in Lake Biwa.
2. The results of comparison of ecology of the two species suggest that interaction of ayu and isaza possibly occurs in cold season when there is no other important competitor.
3. The significance of interspecific competition between them is evaluated as a factor controlling the rate of recruitment of juvenile through analysis of the Pre-war catch statistics.
4. Presence of the compensation between the juvenile stage and the adult one relieve the ayu population of influence of interspecific competition which they will suffer in the stage of juvenile.
5. Competitive processes which will be responsible for increase of mortality and reduction of individual growth are discussed.

     

Analysis of vegetation-environment relationships using a simultaneous equations model

The simultaneous equations model based on regression analysis was adopted to analyse relations between vegetation and environment in a forest reserve in the eastern part of Poland. It allowed a direct analysis of the vegetational variation caused by both environmental factors and interactions between species. In the system sampled several significant interrelations were found, and the ecological importance of particular factors and species was determined. Similar analysis performed by reciprocal averaging did not yield such satisfactory results, because of the equivocal correlation pattern between ecological variables and ordination axes, the dominance of the first axis and the exclusion of interspecific relations.     

Diurnal periodicity of spawning activity of permanently territorial damselfishes (Teleostei: Pomacentridae)

Synopsis Like other congeneric damselfishes, the herbivorous Stegastes altus defends individual feeding territories from heterospecific food competitors, regardless of sex. Females spawned demersal eggs for 31.4 min (n = 25) at the nest in territories of males 0–75 m away from theirs. Throughout the spawning season (June to September), spawning occurred only at dawn, mainly just after sunrise. Daily activity of the fish community showed that potential diurnal food competitors were few or inactive only at dawn and dusk. The frequency of intrusions into the female's territory by heterospecific competitors were as low when she left her territory to spawn at dawn, as they were in the daytime when she defended it. Removal of the female in the daytime resulted in a significant increase in intrusion frequency. An ‘anti-competitor hypothesis’, whereby dawn spawning ensures the food resource in the female's territory seems to explain not only the spawning periodicity in S. altus but also the timing of spawning of other permanently territorial damselfishes. Contribution from the Laboratory of Animal Ecology, Kyoto University, No. 492.     

Transfer of resistance to PLRV titer buildup from Solanum etuberosum to a tuber-bearing Solanum gene pool

Summary Hybrids between Solanum etuberosum and S. pinnatisectum harboring resistance to titer buildup of potato leafroll virus (PLRV) were reciprocally crossed with tuber-bearing wild species S. acaule and S. verrucosum. A total of 47 hybrids with acaule were obtained with the aid of embryo rescue and sterile culturing of embryos from imbibing seeds. All but two hybrids with acaule had low pollen stainabilities or were pollen sterile. Hybrid seeds from crosses with verrucosum were easily obtained, and the triploid progenies were sterile. Hybrid progeny were screened for resistance to PLRV infection by viruliferous green peach aphid and for resistance to titer buildup. Although hybrids did not exhibit resistance to infection, PLRV was not detectable using ELISA. Virus was detected, however, by graft transmission to Datura stramonium. Crosses of fertile acaule-etuberosum-pinnatisectum hybrids with S. phureja, a cultivated diploid, using the latter as pollen parent, produced berries but seed did not complete development and was aborted. Rescue of immature embryos 25 days after pollination by excision from berries and sterile culture produced vigorous, pot-cultured plants. Segregation of susceptible (virus detected) and resistant (virus undetected) progenies suggests simple inheritance.     

Elimination and duplication of particular Hordeum vulgare chromosomes in aneuploid interspecific Hordeum hybrids

Summary Seeds formed in crosses Hordeum lechleri (6x) x H. vulgare (2x and 4x), H. arizonicum (6x) x H. v. (2x), H. parodii (6x) x H. v. (2x), and H. tetraploidum (4x) x H. v. (2x) produced plants at high or rather high frequencies through embryo rescue. Giemsa C-banding patterns were used to analyze chromosomal constitutions and chromosomal locations on the methaphase plate. Among 100 plants obtained from H. vulgare (2x) crosses, 32 plants were aneuploid with 2n=29 (1), 28 (3), 27 (13), 26 (5), 25 (4), 24 (4), or 22 (2); 50 were euploid (12 analyzed), and 18 were polyhaploid (5 analyzed). Four plants had two sectors differing in chromosome number. Two of four hybrids with H. vulgare (4x) were euploid and two were aneuploid. Parental genomes were concentrically arranged with that of H. vulgare always found closest to the metaphase centre. Many plants showed a certain level of intraplant variation in chromosome numbers. Except for one H. vulgare (4x) hybrids, this variation was restricted to peripherally located non-H. vulgare genomes. This may reflect a less firm attachment of the chromosomes from these genomes to the spindle. Interplant variation in chromosome numbers was due to the permanent elimination or, far less common, duplication of the centrally located H. vulgare chromosomes in all 34 aneuploids, and in a few also to loss/gain of non-H, vulgare chromosomes. This selective elimination of chromosomes of the centrally located genome contrasts conditions found in diploid interspecific hybrids, which eliminate the peripherally located genome. The difference is attributed to changed genomic ratios. Derivatives of various H. vulgare lines were differently distributed among euploid hybrids, aneuploids, and polyhaploids. Chromosomal constitutions of hypoploid hybrids revealed a preferential elimination of H. vulgare chromosomes 1, 5, 6, and 7, but did not support the idea that H. vulgare chromosomes should be lost in a specific order. H. vulgare SAT-chromosomes 6 and 7 showed nucleolar dominance. Aneuploidy is ascribed to the same chromosome elimination mechanism that produces haploids in cross-combinations with H. vulgare (2x). The findings have implications for the utilization of interspecific Hordeum hybrids.     

Production and viability of unreduced gametes in triploid interspecific blueberry hybrids

Summary Three triploid (2n=3x=36) blueberry hybrids were obtained by hand-pollinating approximately 7,000 flowers of tetraploid highbush blueberry cultivars (based on Vaccinium corymbosum L.) with pollen from the diploid species V. elliottii Chapm. Meiotic analysis of these triploids revealed trivalents, bivalents and univalents in all metaphase I cells, with lagging chromosomes evident at anaphase I. Pollen of the three triploids was mostly aborted and did not stain with acetocarmine. However, the three triploids did produce from 0.9%–1.3% giant pollen grains that stained with acetocarmine and were present as monads, dyads or triads, rather than the normal tetrads. Pollination of 10,853 flowers of hexaploid V. ashei Reade cultivars with pollen from the triploids produced 266 berries, which averaged fewer than two fully-developed seeds per berry. One triploid clone showed partial female fertility when crossed to hexaploids, self-pollinated, or intercrossed with other triploids. Ploidy levels of the resulting hybrids were determined.Florida Agricultural Experiment Station Journal Series No. 8672     

The influence of habitat and behavioural interactions on the local distribution of the wrasse,Pseudolabrus celidotus

Synopsis The temperate wrasse, Pseudolabrus celidotus (Labridae), was studied in a shallow rocky reef habitat to asses how ecological and behavioural factors influence its within habitat patterns of distribution. Emphasis was placed on examining the mechanisms underlying size/age related changes in dispersion and habitat use. Juveniles (< 100 mm SL) were found to be aggregated whereas adults tended to be more randomly dispersed. This pattern appeared to be a product of both (a) ecological, and (b) behavioural factors. (a) Juveniles were closely associated with shelter (macro-algae) which was located in patches throughout the habitat. Their local distribution was probably not related to the distribution of their major prey items. Shelter dependence appears to decrease with growth and fish switched from feeding on micro-crustaceans present in macro-algae to those associated with bare rock — coralline turf areas. Adults foraged throughout larger home ranges, but fed preferentially in microhabitats where their prey items (e.g. bivalves) were most abundant. (b) Juveniles tended to aggregate into loose foraging schools. This tendency declined with age and was associated with a corresponding increase in the rate of aggressive interactions among individuals of a cohort. Consequently, individuals of the same size became more spaced out as they grew. Between cohort association or aggression was rare and apparently unimportant in determining local patterns of distribution. Many interspecific foraging associations and aggressive interactions were recorded. However, with the probable exception of interspecific territoriality by the blenny Forsterygion varium, these behaviours probably had only a transitory influence on the distribution of the wrasse.     

Tool use by a red howler monkey (Alouatta seniculus) towards a two-toed sloth (Choloepus didactylus)

Among New World monkeys, spontaneous tool use and object manipulation are commonly descirbed inCebus species only. We report here an occurrence of tool manipulation by a wild male red howler monkey (Alouatta seniculus), observed using a stick to softly but repeatedly hit a two toed sloth (Choloepus didactylus) resting in the same tree. The ecological context of this unusual behavior for this quiet species generally showing very little manipulative propensity is discussed.