Three new teosintes (Zea spp., Poaceae) from México.

PREMISE OF THE STUDY: Teosinte species are the closest relatives of maize and represent an important but increasingly rare genetic resource for maize improvement and the study of evolution by domestication. Three morphologically and ecologically distinct teosinte populations were recently discovered in México. The taxonomic status of these rare and endangered populations was investigated by detailed comparisons to previously characterized wild Zea species. • METHODS: Three new teosinte populations were compared to known teosinte taxa on the basis of morphological, ecogeographic, cytological, and molecular characteristics. Phenetic and phylogenetic analyses were performed using morphological and molecular data, respectively. • KEY RESULTS: The newly discovered populations are distinct from each other and from other Zea species to represent three new entities based on their unique combinations of morphological, ecological, ploidy, and DNA markers. A perennial diploid population from Nayarit is distinguished by early maturing plants, and having male inflorescences with few tassel branches and long spikelets. A perennial tetraploid population from Michoacán is characterized by tall and late maturing plants, and having male inflorescences with many branches. An annual diploid population from Oaxaca is characterized by having male inflorescences with fewer branches and longer spikelets than those found in the sister taxa Z. luxurians and Z. nicaraguensis, plants with high thermal requirements, and very long seed dormancy. • CONCLUSIONS: Evidence from multiple independent sources suggests placement of the three new populations of teosinte as distinct entities within section Luxuriantes of the genus Zea. However, more extensive DNA marker or sequence data are required to resolve the taxonomy of this genus.

Direct mapping of density response in a population of B73 x Mo17 recombinant inbred lines of maize (Zea Mays L.).

Maize yield per unit area has dramatically increased over time as have plant population densities, but the genetic basis for plant response to density is unknown as is its stability over environments. To elucidate the genetic basis of plant response to density in maize, we mapped QTL for plant density-related traits in a population of 186 recombinant inbred lines (RILs) derived from the cross of inbred lines B73 and Mo17. All RILs were evaluated for growth, development, and yield traits at moderate (50 000 plants per hectare) and high (100 000 plants per hectare) plant densities. The results show that genetic control of the traits evaluated is multigenic in their response to density. Five of the seven loci significant for final height showed statistical evidence for epistatic interactions. Other traits such as days to anthesis, anthesis-to-silking interval, barrenness, ears per plant, and yield per plant all showed statistical evidence for an epistatic interaction. Locus by density interactions are of critical importance for anthesis-to-silking interval, barrenness, and ears per plant. A second independent experiment to examine the stability of QTL for barrenness in a new environment clearly showed that the multilocus QTL were stable across environments in their differential response to density. In this verification experiment, the four-locus QTL was used to choose lines with the four unfavorable alleles and compare them with the lines with four favorable alleles and the effect was confirmed.

Mapping reciprocal effects and interactions with plant density stress in Zea mays L.

Reciprocal effects are due to genetic effects of the parents (i.e. maternal and paternal effects), cytoplasmic effects and parent-of-origin effects. However, in Zea mays L. the extent to which reciprocal effects exist, or can be attributed to specific underlying components, remains an area of interest and study. Reciprocal effects have been reported by several investigators for various agronomic characters in different types of maize materials for grain and silage usage. Maize geneticists and breeders have recognized reciprocal effects as one source of genetic variability, but the lack of consistency in the observation of these effects, particularly due to stress conditions, has prevented a systematic exploitation of these effects in practical breeding programs. There is mounting molecular evidence for underlying mechanisms in maize, which could be responsible for both the existence, and the instability of reciprocal effects. In this study, we developed population of reciprocal backcrosses based on an initial set of recombinant inbred lines. This population was used for dissecting reciprocal effects into the underlying components (maternal, cytoplasmic and parent-of-origin) effects. We also developed statistical framework to identify and map contributions of specific nuclear chromosomal regions to reciprocal effects. We showed that differences in maternal parents, endosperm DNA and maternally transmitted factors collectively influence reciprocal effects early during the season, and that their influence diluted at later stages. We also found evidence that parent-of-origin effects in the sporophyte DNA existed at all stages and played an important role in establishing differences between reciprocal backcrosses at later developmental stages.

[Searching for retroviral sequences related to human breast cancer]. / En busca de secuencias retrovirales relacionadas con el cáncer de mama humano.

The participation of viruses in mammary carcinogenesis has been largely studied in animals. A model similar to the mouse mammary tumor virus (MMTV) was previously proposed. Several lines of research supported the participation of MMTV in human breast cancer, but these evidences were contradicted when further research was performed. One major issue was the presence of human endogenous retroviral sequences that confounded results reporting MMTV-like sequences in human breast cancer. To overcome this problem we selected a 660 bp sequence of the MMTV env gene with low homology to endogenous sequences and search for a sequence to it using the polymerase chain reaction (PCR). The sequence was found in 38% of the human breast cancers and in 2% of the normal breasts studied. The sequence was not present in tumors from other organs. It was 90-98% homologous to MMTV and only 18% to human endogenous retrovirus (HERV) K-10. It was also detected in some of the positive tumors by Southern blot hybridization using one of the cloned 660 bp as a probe. Using reverse transcriptase PCR, it was possible to demonstrate that the 660 bp sequence is expressed in the majority of the tumors. Also, preliminary experiments revealed that sequences related to the LTR and gag genes of MMTV were present in the DNA of breast tumors. The origin of the MMTV-like sequences in tumor DNA could be the result of integrated MMTV-like sequences derived from a human mammary virus or may represent unknown endogenous sequences that can only be detected in breast tumors.

Female labour force integration and the alleviation of urban poverty: a case study of Kingston, Jamaica.

PIP: The author posits that female labor force integration in Jamaica accomplishes little in alleviating poverty and making maximum use of human resources. Women are forced into employment in a labor market that limits their productivity. Women have greater needs to increase their economic activity due to price inflation and cuts in government spending. During the 1980s and early 1990s the country experienced stabilization and structural adjustment resulting in raised interest rates, reduced public sector employment, and deflated public expenditures. Urban population is particularly sensitive to monetary shifts due to dependency on social welfare benefits and lack of assets. Current strategies favor low wage creation in a supply-side export-oriented economy. These strategies were a by-product of import-substitution industrialization policies during the post-war period and greater control by multilateral financial institutions in Washington, D.C. The World Bank and US President Reagan's Caribbean Basin Initiative stressed export-oriented development. During the 1980s, Jamaican government failed to control fiscal policy, built up a huge external debt, and limited the ability of private businessmen to obtain money for investment in export-based production. Over the decade, uncompetitive production declined and light manufacturing increased. Although under 10% of new investment was in textile and apparel manufacturing, almost 50% of job creation occurred in this sector and 80% of all apparel workers were low-paid women. Devaluation occurred both in the exchange rate and in workers' job security, fringe benefits, union representation, and returns on skills. During 1977-89 women increased employment in the informal sector, which could not remain competitive under devaluation. Women's stratification in the labor market, high dependency burdens, and declining urban infrastructure create conditions of vulnerability for women in Jamaica.^ieng

Evolution of alphaviruses in the eastern equine encephalomyelitis complex.

Evolution of viruses in the eastern equine encephalomyelitis (EEE) complex was studied by analyzing RNA sequences and oligonucleotide fingerprints from isolates representing the North and South American antigenic varieties. By using homologous sequences of Venezuelan equine encephalomyelitis virus as an outgroup, phylogenetic trees revealed three main EEE virus monophyletic groups. A North American variety group included all isolates from North America and the Caribbean. One South American variety group included isolates from the Amazon basin in Brazil and Peru, while the other included strains from Argentina, Guyana, Ecuador, Panama, Trinidad, and Venezuela. No evidence of heterologous recombination was obtained when three separate regions of the EEE virus genome were analyzed independently. Estimates of the overall rate of EEE virus evolution (nucleotide substitution) were 1.6 x 10(-4) substitution per nucleotide per year for the North American group and 4.3 x 10(-4) for the Argentina-Panama South American group. Evolutionary rate estimates for the North American group increased over 10-fold (from about 2 x 10(-5) to 4 x 10(-4)) concurrent with divergence of two monophyletic groups during the early 1970s. The North and South American antigenic varieties diverged roughly 1,000 years ago, while the two main South American groups diverged about 450 years ago. Analysis of multiple strains isolated from an upstate New York transmission focus during the same years suggested that, in certain locations, EEE virus may be relatively isolated for short time periods.

Promoting primary health in Belize.

PIP: This article describes a 2-year project aimed at promoting primary health in a rural area of Belize with little access to health services. 27 mobile clinics were scheduled every 6 weeks. Services focused on immunization, development of a health education program, prenatal and postnatal care, and child health. A correlation was noted between the facilities available in each community (e.g. water supply) and the state of that community's health. Although family planning could not be promoted because of the government's pronatalist policy, birth spacing and breastfeeding were advocated. Project activities in the village of Santa Familia provide an example of community participation in health programs. A local lay midwife was given a traditional birth attenders course and trained to lead health education courses in the village. A community health council was established to initiate 3 projects: preschool nursery, cleaning up of the village, and latrine construction. As part of a campaign against hookworm, schoolchildren are required to wear shoes. The goal of these projects was to ensure that the villages would continue to take an interest in personal and community welfare after the departure of the health workers.^ieng