GENETIC VARIABILITY OF GELIDIUM CANARIENSIS (RHODOPHYTA) DETERMINED BY ISOZYME ELECTROPHORESIS1

The populations of Gelidium canariensis (Grunow) Seoane-Camba from the Canary Islands were analyzed for genetic variability by isozyme electrophoresis in 1989 and 1990. Each population was divided into sporophytic and gametophytic subpopulations. Twenty-three to 27 putative alleles corresponding to 22 gene loci were analyzed. Sev-enteen loci were monomorphic in all six subpopulations, and five were polymorphic in at least one subpopulation. Significant deviations from Hardy-Weinberg equilibrium were found. The amount of genetic variability (percentage of polymorphic loci, mean number of alleles per locus, and average gene diversity) of haploid subpopulations was lower than that of diploid subpopulations. No correlation between genetic distance and geographical distance was found. Low genetic differentiation between sporophytic and gametophytic subpopulations of the same locality was obsewed in two populations. The low genetic diversity and genetic differentiation suggest that the genetic structure of the populations of G. canariensis from the Canary Islands is due to a combination of founder effects and the predominance of asexual reproduction. Initial differences in gene frequencies may have persisted because of insufficient time to reach a higher level of differentiation.     

Seed protein and isozyme variations in Triticum tauschii (Aegilops squarrosa)

Sixty Triticum tauschii (Aegilops squarrosa, 2n=2x=14, DD) accessions were evaluated for the variability of high-molecular-weight (HMW) glutenins, gliadins and isozymes of seed esterase, -amylase and glucose-phosphate isomerase. Wide variability was observed for HMW-glutenins and gliadins. The implications of unique HMW-glutenin alleles for quality parameters are discussed. Isozyme evaluations indicated more variability for the Est-D ^t 5 locus as compared to the Est-D5 of bread-wheat. The polymorphism for -Amy-D ^t 1 was less than that of -Amy-D1. Similar to the bread-wheat situation, Gpi-D ^t 1 showed no polymorphism. The variability observed with the traits evaluated can be readily observed in T. turgidum x T. tauschii synthetic hexaploids (2n=6x=42, AABBDD) suggesting that T. tauschii accessions may be a rich source for enhancing the genetic variability of T. aestivum cultivars.     

Different CMS sources found in Beta vulgaris ssp maritima: mitochondrial variability in wild populations revealed by a rapid screening procedure

Summary Mitochondrial DNA (mtDNA) variation in natural Beta maritima populations has been characterized by way of Southern blot hybridizations of total DNA using non-radioactive probes and chemiluminescent detection. It was found that the previously described N (normal) mitochondrial type could be subdivided into three subtypes. A new mitochondrial genotype (type R) was distinguished in addition to the previously described type S. Both are male-sterile cytoplasms and can produce a. segregation of sexual phenotypes in their progenies depending on the nuclear background. The populations contained at least two to four different mitochondrial genotypes.     

Morphological differentiation in Carduelis finches: Adaptive vs. constraint models

In this study we show that morphological diversification in the avian genus Carduelis (Carduelinae) has to a large extent been conservative. Using multivariate methods, we found only minor deviations from the common (ancestral) body-plan. In particular, variation in bill morphology was found to be more conservative than variation in other parts of the body. We argue that constraint models of population differentiation can successfully account for the variation in bill morphology in this genus, but are less successful in accounting for variation in other traits. This can be interpreted as a result of long-term overall stabilizing selection for a certain bill morphology which is related to the way the birds open seeds. A trait combination that is adaptive on the evolutionary time scale may thus act as a constraint on changes in bill morphology on the microevolutionary scale. We conclude that the most parsimonious explanation for low divergence in bill morphology in this genus is that all species have retained the ancestral bill morphology. This may mean that each species chooses its environment rather than being moulded by it. This argument seems to apply to bill morphology, but other traits studied in this genus appear to have evolved in a less constrained fashion. A new index of morphometric integration is introduced to describe covariance structures.     

桑白蚧的重要寄生蜂——桑白蚧恩蚜小蜂的鉴别与利用

桑白蚧恩蚜小蜂Encarsia(=Prospaltella)berlesel(Howard)是寄生桑白蚧Pseudaulacaspls pentagona(Targioni-Tozzctti)的重要寄生蜂,许多国家进行了引进移植,对控制桑白蚧的为害取得明显的成效．本记述了桑白蚧恩蚜小蜂形态特征的鉴别。以及各国引进利用的概况．并讨论了利用寄生蜂防治桑白蚧的重要性．     

Tube-snouted gymnotiform and mormyriform fishes: convergence of a specialized foraging mode in teleosts

Synopsis African mormyriform and South American gynmotiform fishes are unique among freshwater fishes in their abilities to generate and perceive an electrical field that aids in orientation, prey detection, and communication. Here we present evidence from comparative ecology and morphology that tube-snouted electric fishes of the generaSternarchorhynchus (Apteronotidae) andCampylomormyrus (Mormyridae) may be unique among fishes in their mode of foraging by grasp-suction. The grasp-suction mode of feeding is a specialization for extracting immature stages of aquatic insects that burrow into, or hide within, interstitial spaces and holes in matrices of compacted clay particles that form the channel bottom of many tropical lowland rivers. Ecomorphological implications of the remarkable evolutionary convergence for this specialized mode of foraging by tube-snouted electric fishes provide a challenge to Liem's (1984, 1990) theory of separate aquatic and terrestrial vertebrate feeding modes.Invited Editorial     

Incidence and genetic diversity of raspberry bushy dwarf virus (RBDV) in Rubus spp. in Turkey

Raspberry bushy dwarf virus (RBDV), recently renamed to Idaeovirus rubi, is one of the most common viruses infecting Rubus species worldwide but there is still a limited number of genome sequences available in the GenBank database and the majority of the sequences include partial sequences of RNA-1 and RNA-2. The distribution and incidence of RBDV in main raspberry and blackberry growing provinces in Turkey were monitored during 2015–2019 and 537 Rubus spp. samples were tested by both DAS-ELISA and RT-PCR. Among the tested samples, 36 samples tested positive for RBDV by DAS-ELISA and 67 samples by RT-PCR. There was relatively low nucleotide diversity among the Turkish isolates. Turkish isolates shared 93%–97.7%, 84.3%–98.9%, and 85%–99.2% nucleotide sequence identities with available sequences in the GenBank, in partial RNA-1, movement protein (MP) and coat protein (CP) genes, respectively. In the phylogenetic tree constructed for RNA-1, MP, and CP sequences, all Turkish raspberry isolates were clustered in a distinct clade. However, the blackberry isolates showed considerable variation in nucleotide sequences and were placed in three distinct groups. The divergent blackberry isolates showed high variability in MP (84.5%–89.3%) and CP (85.5%–89.7%) regions and were placed in a distinct group. The rest of blackberry isolates clustered together with sweet cherry RBDV isolates adjacent to the grapevine clade or together with raspberry isolates. The comparative analysis conducted on three RNA segments of RBDV highlighted the high sequence diversity of Turkish RBDV isolates. This study also emphasizes the importance of regular monitoring of RBDV infections in Turkey, with special regard to those Rubus spp. and grapevine accessions employed in conservation and selection programmes. In particular, the presence of new RBDV genetic variants and infection of Rubus species must be taken into account to choose a correct detection protocol and management strategy.     

Population structure of mud flounder Paralichthys orbignyanus from the south-western Atlantic Ocean

The mud flounder Paralichthys orbignyanus (Pleuronectiformes, Paralichthyidae) inhabits shallow waters of low salinities and mud bottoms in the temperate marine coastal regions of the Bonaerensean Ecoregion of the Argentinean Biogeographic Province in the south-western Atlantic Ocean. Specimens of P. orbignyanus were collected from Lagoa dos Patos (LDP) (southern Brazil), Mar Chiquita (MCH) and Marisol (MAR) both located in Buenos Aires (Argentina), and San Antonio Oeste (SAO) in the San Matías Gulf, Rio Negro (Argentina). A fragment of the mitochondrial DNA of the Control Region and seven microsatellite loci were characterized. In the Control Region, P. orbignyanus showed high variability, low nucleotide diversity, mild population expansion and a coalescence time of 35,000 years before the present. Flounders provided evidence of a genetic structure between the sampling sites LDP, MCH, MAR vs. SAO. On the other hand, P. orbignyanus displayed a lower to moderate contemporary genetic structure among all samples except between LDP and MCH. With no evidence of isolation by distance, this analysis supports a model of limited gene flow that is likely to be associated with a consistent larvae retention in all sampling sites. In addition, the present connectivity is ascribed to a lower migration process from SAO in the San Matías Gulf congruent with the prevailing littoral drift.     

Seasonal dynamics of the association between sweet potato and vesicular-arbuscular mycorrhizal fungi

To better understand the behavior of selected vesicular-arbuscular mycorrhizal (VAM) isolates in the field, we documented the growth of roots, root hairs, and VAM colonization of inoculated and noninoculated sweet potato plants (Ipomea batatas (L.) Lam. cv White Star) over a growing season. We also determined the seasonal dynamics of P and Zn uptake, and shoot and storage-root growth. Shoot cuttings were inoculated with an isolate of either Glomus etunicatum Becker and Gerdemann or Acaulospora rugosa Mortan, or were not inoculated, and were harvested 2, 4, 8, 13, 20, and 27 weeks after planting (WAP). At each harvest, roots were sampled at 0 to 30, 30 to 60, and 60 to 90 cm depths and at 0, 23, 83, and 116 cm from the base of the shoot. At the end of the study, the roots of three non-inoculated plants were sampled by soil horizon. Inoculation had no affect on shoot growth or total shoot uptake of P and Zn; shoot dry mass and P and Z content increased rapidly up to 20 WAP, while shoot length continued to increase through 27 WAP. Shoot-P concentration of plants inoculated with A. rugosa at 2 and 8 WAP were higher than the noninoculated plants, while shoot-Zn concentration was not affected by inoculation. Storage-root yields of inoculated plants were higher than yields for noninoculated plants. Root length density, and percentage of root length with root hairs and VAM colonization were highest and most dynamic near the base of the plant. Percentage of root length colonization by VAM fungi was highest in the E2 horizon, intermediate in the Bh horizon, and lowest in the Ap horizon. Percentage of root length with root hairs had the opposite pattern. Intensive measurements of root characteristics close to the base of the plant, and shoot P-content and concentration during the period of rapid yield production, provided the most useful data for evaluating the activity of effective isolates.Published as Florida Agricultural Experimental Station Journal Series No. R-02576