Experiences of The Network: Towards Unity for Health Women and Health Taskforce.

CONTEXT: Women's health is an often neglected component of health professions education despite the well-documented need to improve the health status of women, especially in low income countries. This paper was written on behalf of all members of The Network: Towards Unity for Health Women and Health Taskforce (WHTF) which unites leaders in women's health and higher education from different countries around the world. The WHTF objectives include teaching health providers the skills and knowledge necessary to improve care to women; encouraging universities to partner with community women's groups; promoting the inclusion of women's rights and gender issues in curricula; and cultivating leadership among female health professions students. OBJECTIVE/CONTENT: The main goal of the paper is to provide an overview of the collaborative processes, the accomplishments and the lessons learned in this project since the early 1990s. It includes the history and evolution of the Taskforce; the importance of human rights and gender issues in approaching women's health; teaching tools--the Women and Health Learning Package (WHLP); implementation of WHLP in health professions education and community settings; and main outcomes and future challenges. The WHLP was implemented in fourteen universities and seven university community programs. A new edition of WHLP will be available in 2009. CONCLUSION: The WHTF is a model of south-south collaboration in health professions education and community programs to improve women's health. It has been successful in reaching universities and communities all over the globe and provides a model for other education, health and community issues.

Distribution of Papaya ringspot virus and Papaya mosaic virus in Papaya Plants (Carica papaya) in Mexico.

We report the results of a survey for the presence of Papaya ringspot virus (PRSV) along the coasts of the Gulf of Mexico and the Pacific Ocean, in 15 federal states of Mexico that account for over 98% of the national papaya production. More than 80 locations were visited in 58 counties. Out of a total of 267 papaya leaf samples, 157 tested positive for PRSV. We tested for the presence of three other viruses because of the occurrence of severe, atypical symptoms in plantations. Only Papaya mosaic virus (PapMV) was detected. PRSV was present in every county. PapMV was less frequent, but its overall distribution was almost identical. PRSV and PapMV occurred in single or mixed infections of papaya and other host species that could function as virus reservoirs. We investigated the diversity of the coat protein (CP) sequences of 36 PRSV isolates. The amino acid sequence divergence among all isolates ranged from 0.4 to 9.9%, and was comparable to that found in other regions of the world. In contrast to most of these world regions, there is a clear correlation between CP sequence variation and the geographical origins of the virus isolates.

Ascertaining maternal and paternal lineage within Musa by chloroplast and mitochondrial DNA RFLP analyses.

In banana, the maternal transmission of chloroplast DNA and paternal transmission of the mitochondrial DNA provides an exceptional opportunity for studying the maternal and paternal lineage of clones. In the present study, RFLP combined with hybridization of heterologous mitochondrial and chloroplastic probes have been used to characterize 71 wild accessions and 131 diploid and 103 triploid cultivated clones. In additon to Musa acuminata and Musa balbisiana, other species from the four Musa sections were studied to investigate their contribution to the origin of cultivated bananas. These molecular analyses enable the classification of the Musa complex to be discussed. Results ascertain relationships among and between the wild accessions and the mono- and interspecific diploid and triploid bananas, particularly for the acuminata genome. Parthenocarpic varieties are shown to be linked to M. acuminata banksii and M. acuminata errans, thus suggesting that the first center of domestication was in the Philippines - New Guinea area.

Genetic mapping of maize streak virus resistance from the Mascarene source. I. Resistance in line D211 and stability against different virus clones.

Maize streak virus (MSV) disease may cause significant grain yield reductions in maize in Africa. Réunion island maize germplasm is a proven source of strong resistance. Its genetic control was investigated using 123 RFLP markers in an F(2) population of D211 (resistant) × B73 (susceptible). This population of 165 F(2:3) families was carefully evaluated in Harare (Zimbabwe) and in Réunion. Artificial infestation was done with viruliferous leafhoppers. Each plant was rated weekly six times after infestation on a 1-9 scale previously adjusted by image analysis. QTL analyses were conducted for each scoring date, and for the areas under the disease, incidence and severity progress curves. The composite interval mapping method used allowed the estimation of the additive and dominance effects and QTL × environment interactions. Heritabilities ranged from 73% to 98%, increasing with time after infestation. Resistance to streak virus in D211 was provided by one region on chromosome 1, with a major effect, and four other regions on chromosomes 2, 3 (two regions) and 10, with moderate or minor effects. Overall, they explained 48-62% of the phenotypic variation for the different variables. On chromosome 3, one of the two regions seemed to be more involved in early resistance, whereas the second was detected at the latest scoring date. Other QTLs were found to be stable over time and across environments. Mild QTL × environment interactions were detected. Global gene action appeared to be partially dominant, in favor of resistance, except at the earliest scoring dates, where it was additive. From this population, 32 families were chosen, representing the whole range of susceptibility to MSV. They were tested in Réunion against three MSV clones, along with a co-inoculation of two of them. Virulence differences between clones were significant. There were genotype × clone interactions, and these were more marked for disease incidence than for severity. Although these interactions were not significant for the mean disease scores, it is suggested that breeders should select for completely resistant genotypes.

Genetic mapping of maize streak virus resistance from the Mascarene source. II. Resistance in line CIRAD390 and stability across germplasm.

The streak disease has a major effect on maize in sub-Saharan Africa. Various genetic factors for resistance to the virus have been identified and mapped in several populations; these factors derive from different sources of resistance. We have focused on the Réunion island source and have recently identified several factors in the D211 line. A second very resistant line, CIRAD390, was crossed to the same susceptible parent, B73. The linkage map comprised 124 RFLP markers, of which 79 were common with the D211×B73 map. A row-column design was used to evaluate the resistance to maize streak virus (MSV) of 191 F(2:3) families under artificial infestation at two locations: Harare (Zimbabwe) and in Réunion island. Weekly ratings of resistance were taken and disease incidence and severity calculated. QTL analyses were conducted for each scoring date and for the integration over time of the disease scores, of incidence, and of severity. Heritability estimates (71-98%) were as high as for the D211×B73 population. Eight QTLs were detected on chromosomes 1, 2, 3, 5 (two QTLs), 6, 8, and 10. The chr1-QTL explained the highest proportion of phenotypic variation, about 45%. The QTLs on chromosomes 1, 2, and 10 were located in the same chromosomal bin as QTLs for MSV resistance in the D211×B73 population. In a simultaneous fit, QTLs explained together 43-67% of the phenotypic variation. The QTLs on chromosomes 3, 5, and 6 appeared to be specific for one or the other component of the resistance. For the chr3-QTL, resistance was contributed by the susceptible parent. There were significant QTL × environment interactions for some of the variables studied, but QTLs were stable in the two environments. They also appeared to be stable over time. Global gene action ranged from partial dominance to overdominance, except for disease severity. Some additional putative QTLs were also detected. The major QTL on chromosome 1 seemed to be common to the other sources of resistance, namely Tzi4, a tolerant line from IITA, and CML202 from CIMMYT. However, the distribution of the other QTLs within the genome revealed differences in Réunion germplasm and across these other resistance sources. This diversity is of great importance when considering the durability of the resistance.

Mapping diplosporous apomixis in tetraploid Tripsacum: one gene or several genes?

Polyploids in Tripsacum, a wild relative of maize, reproduce through the diplosporous type of apomixis, an asexual mode of reproduction through seeds. Diplosporous apomixis involves both the failure of meiosis and the parthenogenetic development of the unreduced gametes, resulting in progenies that are exact genetic copies of the mother plant. Apomixis is believed to be controlled by one single dominant allele, responsible for the whole developmental process. Construction of a linkage map for the chromosome controlling diplosporous apomixis in Tripsacum was carried out in both tetraploid-apomictic and diploid-sexual Tripsacum species using maize restriction fragment length polymorphism (RFLP) probes. A high level of collinearity was observed between the Tripsacum chromosome carrying the control of apomixis and a duplicated segment in the maize genome. In the apomictic tetraploid, there was a strong restriction to recombination, as compared to the corresponding genomic segment in sexual plants and maize. This suggests that apomixis, although inherited as a single Mendelian allele, might really be controlled by a cluster of linked loci. The analysis also revealed the tetrasomic nature of the inheritance of the chromosomal segment controlling apomixis, which contradicts the usually accepted hypothesis of an allopolyploid origin of apomictic species. The implications of these data for the transfer of apomixis into cultivated crops are discussed, and a new approach to studying the genetics of apomixis, based on comparative mapping, is proposed.

Non-Mendelian transmission of apomixis in maize-Tripsacum hybrids caused by a transmission ratio distortion.

Apomixis is a mode of asexual reproduction through seeds. The apomictic process bypasses both meiosis and egg cell fertilization, producing offspring that are exact genetic replicas of the mother plant. In the Tripsacum agamic complex, all polyploids reproduce through the diplosporous type of apomixis, and diploids are sexual. In this paper, molecular markers linked with diplospory were used to analyse various generations of maize-Tripsacum hybrids and backcross derivatives and to derive a model for the inheritance of diplosporous reproduction. The results suggest that the gene or genes controlling apomixis in Tripsacum are linked with a segregation distorter-type system promoting the elimination of the apomixis alleles when transmitted through haploid gametes. Hence, this model offers an explanation of the relationship between apomixis and polyploidy. The evolutionary importance of this mechanism, which protects the diploid level from being invaded by apomixis, is discussed.

Detection of quantitative trait loci associated with leaf rust resistance in bread wheat.

Leaf rust, caused by Puccinia recondita Rob. ex Desm., is a common disease in wheat. The objective of this study was to develop molecular markers associated with the quantitative trait loci (QTLs) putatively conferring durable leaf rust resistance in Triticum aestivum L. em. Thell. A population of 77 recombinant inbred lines (RILs) developed from 'Parula' (resistant) and 'Siete Cerros' (moderately susceptible) was used. Bulked segregant analysis was done using random amplified polymorphic DNAs (RAPDs) with DNA enriched for low-copy sequences using hydroxyapatite chromatography. Out of 400 decamer primers screened, 3 RAPD markers were identified between the bulk of the most resistant and the bulk of the most susceptible lines. These were cloned and used as probes on the RILs in Southern hybridizations. Two probes revealed two tightly linked loci. One-way analysis of variance showed that these two loci, and another revealed by the third probe, were linked to QTLs controlling leaf rust resistance based on data taken from 2 years of replicated field trials. Cytogenetic analysis placed the two tightly linked loci on the long arm of chromosome 7B. The third probe detected loci located on the short arms of chromosomes 1B and 1D. It is suggested that the QTL detected on 7BL may well be homoeoallelic to Lr34.

QTL for insect resistance and drought tolerance in tropical maize: prospects for marker assisted selection.

Insects and drought cause severe losses in the production of maize in many developing countries. Conventional breeding efforts to enhance the level of resistance to a number of insect pests and tolerance to drought have been successful, although only through large efforts of many breeders and over a large period of time. Continued improvements will only be possible through substantial investment of resources. Recently, success in identifying quantitative trait loci (QTL) in several plant species using various molecular marker systems offers alternative methods for accelerating conventional breeding programs. As the first step towards using molecular markers in CIMMYT's maize breeding program, restriction fragment length polymorphisms (RFLPs) have been used to understand the genetic basis of resistance to two corn borer species, southwestern corn borer and sugarcane borer, and to one major component of drought tolerance, anthesis-silking interval. A number of QTL with effects large enough to be regarded as significant in breeding were detected for each of these traits and many of them presented stable effects over environments. While variability in the number and location of QTL has been found when compared across populations, several loci were found to be quite consistent. Simple calculations can be made which estimate that the total genetic potential in maize for these traits is high. It is argued that to ultimately access and manipulate this potential, the use of linked molecular markers as indirect selectable markers is both feasible and necessary.

Identification of quantitative trait loci under drought conditions in tropical maize. 1. Flowering parameters and the anthesis-silking interval.

Drought is an important climatic phenomenon which, after soil infertility, ranks as the second most severe limitation to maize production in developing countries. When drought stress occurs just before or during the flowering period, a delay in silking is observed, resulting in an increase in the length of the anthesis-silking interval (ASI) and in a decrease in grain yield. Selection for reduced ASI in tropical open-pollinated varieties has been shown to be correlated with improved yields under drought stress. Since efficient selection for drought tolerance requires carefully managed experimental conditions, molecular markers were used to identify the genomic segments responsible for the expression of ASI, with the final aim of developing marker-assisted selection (MAS) strategies. An F2population of 234 individuals was genotyped at 142 loci and F3 families were evaluated in the field under several water regimes for male flowering (MFLW), male sterility (STER), female flowering (FFLW) and ASI. The genetic variance of ASI increased as a function of the stress intensity, and the broad-sense heritabilites of MFLW, FFLW and ASI were high under stress conditions, being 86%, 82% and 78%, respectively. Putative quantitative trait loci (QTLs) involved in the expression of MFLW and/or FFLW under drought were detected on chromosomes 1, 2, 4, 5, 8, 9 and 10, accounting for around 48% of the phenotypic variance for both traits. For ASI, six putative QTLs were identified under drought on chromosomes 1, 2, 5, 6, 8 and 10, and together accounted for approximately 47% of the phenotypic variance. Under water stress conditions, four QTLs were common for the expression of MFLW and FFLW, one for the expression of ASI and MFLW, and four for the expression of ASI and FFLW. The number of common QTLs for two traits was related to the level of linear correlation between these two traits. Segregation for ASI was found to be transgressive with the drought-susceptible parent contributing alleles for reduced ASI (4 days) at two QTL positions. Alleles contributed by the resistant line at the other four QTLs were responsible for a 7-day reduction of ASI. These four QTLs represented around 9% of the linkage map, and were stable over years and stress levels. It is argued that MAS based on ASI QTLs should be a powerful tool for improving drought tolerance of tropical maize inbred lines.

Detection of the apomictic mode of reproduction in maize-Tripsacum hybrids using maize RFLP markers.

Polyploid plants in the genus Tripsacum, a wild relative of maize, reproduce through gametophytic apomixis of the diplosporous type, an asexual mode of reproduction through seed. Moving gene(s) responsible for the apomictic trait into crop plants would open new areas in plant breeding and agriculture. Efforts to transfer apomixis from Tripsacum into maize at CIMMYT resulted in numerou intergeneric F1 hybrids obtained from various Tripsacum species. A bulk-segregant analysis was carried out to identify molecular markers linked to diplospory in T. dactyloides. This was possible because of numerous genome similarities among related species in the Andropogoneae. On the basis of maize RFLP probes, three restriction fragments co-segregating with diplospory were identified in one maize-Tripsacum dactyloides F1 population that segregated 1∶1 for the mode of reproduction. The markers were also found to be linked in the maize RFLP map, on the distal end of the long arm of chromosome 6. These results support a simple inheritance of diplospory in Tripsacum. Manipulation of the mode of reproduction in maize-Tripsacum backcross generations, and implications for the transfer of apomixis into maize, are discussed.

RFLP diversity in cultivated sorghum in relation to racial differentiation.

Careful assessment of the comparative diversity for molecular markers and for potentially-useful morpho-agronomic traits is paramount to the analysis of a genome through the mapping of favorable genes. Sorghum (Sorghum bicolor ssp.bicolor) varieties are traditionally classified into five races on the basis of morphological traits, especially panicle and grain traits. Isozyme diversity has provided a new insight into genetic diversity, and showed a marked geographic structure. We performed RFLP analysis on 94 varieties, chosen to represent the main cross combinations (race × geographic origin), using 35 maize probes that detect polymorphism with at least one of the two restriction enzymesHindIII andXbaI. A total of 50 polymorphic probe-enzyme combinations yielded 158 polymorphic bands. The bicolor race appeared highly variable and included many rare markers. Among the other races multivariate analysis of the data differentiated six clusters corresponding, by decreasing magnitude of divergence, to: the margaritiferum types (a sub-race of race guinea); the guinea forms from western Africa; race caudatum; race durra; race kafir; and the guinea forms from southern Africa.The apparent geographic differentiation was related to the contrasting distribution of these races and to a higher similarity between races localized in southern Africa. The data agree with the current hypotheses on sorghum domestication but reveal associations between neutral markers and traits probably highly subjected to human selection. Whether such associations will be observed with other useful traits, and to what extent they are maintained by genetic linkage, is worth exploring.

A molecular marker-based linkage map of diploid bananas (Musa acuminata).

A partial molecular linkage map of the Musa acuminata diploid genome is presented. This map is based on 58 RFLP, four isozyme and 28 RAPD markers segregating in an F2 population of 92 individuals. A total of 90 loci was detected, 77 of which were placed on 15 linkage groups while 13 segregated independently. Segregation distortions were shown by 36% of all loci, mostly favoring the male parent. Chromosome structural rearrangements were believed to be one of the main causes of these distortions. The use of genetic linkage data to further the genetic and evolutionary knowledge of the genus Musa, as well as to help improve the design of breeding strategies, is discussed.