Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.     

The host range of Tobacco streak virus in India and transmission by thrips

Tobacco streak virus (TSV) recently caused an epidemic in peanut (= groundnut, Arachis hypogaea) crops in Andhra Pradesh, India. In the epidemic area TSV occurred in many widely distributed weeds of which Parthenium hysterophorus probably plays a major role in its spread by thrips. Three thrips species, Megalurothrips usitatus, Frankliniella schultzei and Scirtothrips dorsalis were vectors in the presence of infected pollen. Of crop species, Helianthus annuus (sunflower) and Tagetes patula (marigold) could act as sources of inoculum. In limited tests, the virus was not seed‐transmitted in the peanut cultivar JL‐24 or in the sunflower hybrids KBSH‐41, ‐42, ‐44, and ‐50, MSFH‐17 and ZSH‐976. Strategies adopted to reduce the incidence of TSV are discussed.     

Seasonality of canopy invertebrate communities in eucalypt forests of eastern and western Australia

Abstract Chemical knockdown procedures were used to sample canopy arthropods at 3 month intervals over 1 year at two sites, one in eastern Australia and the other in western Australia. Samples were taken from narrow-leaved ironbark, Eucalyptus crebra, and grey box, Eucalyptus moluccana, in the east and from jarrah, Eucalyptus marginata, and marri, Eucalyptus calophylla, in the west. Arthropods were more abundant on trees in eastern Australia and exhibited different seasonal patterns from those in the west. Members of different functional groups exhibited different seasonal patterns, with some herbivorous groups responding to times of leaf production, decomposers and fungus feeders responding to high moisture availability, and predators/parasites responding to the abundance of food items. Seasonal variability was slightly higher in the west, possibly reflecting the greater seasonal amplitude in rainfall. In the eastern forest, proportionately more taxa peaked in spring or summer and declined to minimum numbers in winter. In the western forest several taxa attained peak numbers in autumn, winter or spring, while others declined to minimum values in winter or summer. The phenological patterns of canopy arthropods appear to be linked to the condition of the host plant and/or to climatic factors. Comparison of the western Australian data to those from a second year of sampling at a time when rainfall was greater and fell later into the season indicated that variability in arthropod numbers between years can be as great as that between seasons. Implications of the variability in seasonal and annual patterns of canopy invertebrate communities are discussed in relation to the need for long-term sampling and in relation to evaluating the impact of disturbance on forest communities.     

Attachment microbes antagonistic against Botrytis cinerea—biological control and scanning electron microscope studies in vivo

Bacteria and yeasts, selected by an attachment assay for their ability to adhere to Botrytis cinerea hyphae or conidia, were evaluated for biocontrol potential against B. cinerea on excised tomato stems. Eight of the 12 bacteria and seven of the eight yeast isolates conferred 90% to 100% biocontrol activity when antagonist populations were applied at three to 80 times the pathogen inoculum density. Biocontrol was maintained at similar levels when biocontrol agent (BCA) application was delayed up to 48 h after pathogen challenge. Scanning electron microscopy showed extensive colonisation of B. cinerea mycelium or conidia by many of these isolates and also evidence of pathogen degradation. The biocontrol efficacy and potential for the assay are discussed with respect to cell-to-cell adhesion as a vehicle to deliver antagonistic mechanisms to highly specific pathogen sites.     

Seasonal abundance, biting cycle and parity of the mosquito Haemagogus leucocelaenus in Trinidad, West Indies

Adult female populations of Haemagogus leucocelaenus (Dyar and Shannon), the sylvan vector of yellow fever, were monitored weekly during 1981–82 by human collectors on the ground at Point Gourde in Chaguaramas Forest, 16 km west of Port of Spain, Trinidad.
Hg.leucocelaenus showed only diurnal landing activity, from 06.00 to 18.00 hours (sunrise to sunset, universal time), with a single peak of activity between 10.00 and 14.00 hours.
Densities of Hg.leucocelaenus during the wet season (May–November) were about double the level recorded during the dry season (December–April).
Monthly parous rates averaged 53.9% (range 25–90%) and some females were up to five-pars. Retained eggs (range 2–6, mean 4/female) were found in the ovaries of 0.34% of landing females, all of which had stage 1 ovarian follicles for the next gonotrophic cycle. Therefore blood-feeding is not inhibited by egg retention. Hg. leucocelaenus vector potential is reappraised in the light of these findings.     

Association of <Emphasis Type="Italic">ADAM33</Emphasis> gene polymorphisms with adult-onset asthma and its severity in an Indian adult population

ADAM33, a member of the ADAM (a disintegrin and metalloprotease) gene family, is an asthma susceptibility gene originally identified by positional cloning. In the present study, we investigated the possible association of five single-nucleotide polymorphisms (SNPs) in the ADAM33 (rs511898, rs528557, rs44707, rs597980 and rs2787094) with adult-onset asthma in an Indian population. The study included 175 patients with mild intermittent (n = 44), mild persistent (n = 108) or moderate persistent (n = 23) subgroups of asthma, and 253 nonasthmatic control individuals. SNPs were genotyped with the help of restriction fragment length polymorphism polymerase chain reaction (RFLP-PCR) method, and data were analysed using chi-square test and logistic regression model. Bonferroni’s correction for multiple comparisons was applied for each hypothesis. Genotypes and allele frequencies of SNPs rs511898 and rs528557 were significantly associated with adult-onset asthma (P = 0.010-<0.001). A significant association of the homozygous mutant genotype and mutant alleles of SNPs rs2787094, rs44707 and rs597980 with the asthma was also observed (P = 0.020-<0.001). A positive association between asthma and haplotypes AGCCT, GGCCT, AGACT, GCAGT, GGACT, ACCCC and AGACC were also found (P = 0.036-<0.001, OR = 2.07–8.49). Haplotypes AGCGT, GCAGC, ACAGC, ACAGT, GGAGC and GGCGT appear to protect against asthma (P = 0.013-<0.0001, OR = 0.34–0.10). Our data suggest that ADAM33 gene polymorphisms serve as genetic risk factors for asthma in Indian adult population.     

Isolation by environmental distance in mobile marine species: molecular ecology of franciscana dolphins at their southern range

The assessment of population structure is a valuable tool for studying the ecology of endangered species and drafting conservation strategies. As we enhance our understanding about the structuring of natural populations, it becomes important that we also understand the processes behind these patterns. However, there are few rigorous assessments of the influence of environmental factors on genetic patterns in mobile marine species. Given their dispersal capabilities and localized habitat preferences, coastal cetaceans are adequate study species for evaluating environmental effects on marine population structure. The franciscana dolphin, a rare coastal cetacean endemic to the Western South Atlantic, was studied to examine these issues. We analysed genetic data from the mitochondrial DNA and 12 microsatellite markers for 275 franciscana samples utilizing frequency‐based, maximum‐likelihood and Bayesian algorithms to assess population structure and migration patterns. This information was combined with 10 years of remote sensing environmental data (chlorophyll concentration, water turbidity and surface temperature). Our analyses show the occurrence of genetically isolated populations within Argentina, in areas that are environmentally distinct. Combined evidence of genetic and environmental structure suggests that isolation by distance and a process here termed isolation by environmental distance can explain the observed correlations. Our approach elucidated important ecological and conservation aspects of franciscana dolphins, and has the potential to increase our understanding of ecological processes influencing genetic patterns in other marine species.