Metaphase-I analysis of a Triticum aestivum x T. monococcum hybrid by the C-banding technique

Summary The meiotic pairing behaviour at metaphase I of a Triticum aestivum×Triticum monococcum hybrid has been studied by means of the C-banding technique to ascertain the homology between the chromosomes in the A genome of the two species. The technique allowed the A and B genome chromosomes and the 2D, 3D and 5D chromosomes to be identified. Differences in the level of chromosome pairing in the A genome were noted. The T. monococcum 4A chromosome did not pair with any of the T. aestivum chromosomes in any of the metaphase I cells analysed. Two reciprocal translocations between the 2B and 2D chromosomes on one side and the 2A and 3D on the other side have been identified. The usefulness of the C-banding technique in the study of chromosome homology among species related to wheat is discussed.     

Marker-based screening of maize inbred lines using support vector machine regression

The phenomenon of heterosis is widely used in hybrid breeding programmes, despite the fact that no satisfactory molecular explanation is available. Estimators of quantitative genetic components like GCA and SCA values are tools used by the plant breeder to identify superior parental individuals and to search for high heterosis combinations. Obtaining these estimators usually requires the creation of new parental combinations and testing their offspring in multi-environment field trials. In this study we explore the use of ɛ-insensitive Support Vector Machine Regression (ɛ-SVR) for the prediction of GCA and SCA values from the molecular marker scores of parental inbred lines as an alternative to these field trials. Prediction accuracies are obtained by means of cross-validation on a grain maize data set from the private breeding company RAGT R2n. Results indicate that the proposed method allows the routine screening of new inbred lines despite the fact that predicting the SCA value of an untested hybrid remains problematic with the available molecular marker information and standard kernel functions. The genotypical performance of a testcross hybrid, originating from a cross between an untested inbred line and a well-known complementary tester, can be predicted with moderate to high accuracy while this cannot be said for a cross between two untested inbred lines.     

QTL mapping of a partial resistance to the corn delphacid‐transmitted viruses in Lepidopteran‐resistant maize line Mp705

A partial resistance to maize mosaic virus (MMV) and maize stripe virus (MStV) was mapped in a RILs population derived from a cross between lines MP705 (resistant) and B73 (susceptible). A genetic map constructed from 131 SSR markers spanned 1399 cM with an average distance of 9.6 cM. A total of 10 QTL were detected for resistance to MMV and MStV, using composite interval mapping. A major QTL explaining 34–41% of the phenotypic variance for early resistance to MMV was detected on chromosome 1. Another major QTL explaining up to 30% of the phenotypic variation for all traits of resistance to MStV was detected in the centromeric region of chromosome 3 (3.05 bin). After adding supplementary SSR markers, this region was found to correspond well to the one where a QTL of resistance to MStV already was located in a previous mapping study using an F₂ population derived from a cross between Rev81 and B73. These results suggested that these QTL of resistance to MStV detected on chromosome 3 could be allelic in maize genome.     

A new alpha-methylene gamma-lactone sesquiterpene from Hedyosmum arborescens

A new sesquiterpene lactone, 7alpha,10alpha-epoxy-1alpha(H),5alpha(H)-guaia-3,11(13)-dien-8alpha,12-olide, was isolated from the leaves of Hedyosmum arborescens. The structure of this unusual 7,10-epoxy-guaianolide was determined by spectroscopic methods, particularly one- and two-dimensional 1H and 13C NMR.     

Remittances sent by a growing altruistic diaspora: How do they grow over time?

Abstract: This paper investigates theoretically the time pattern of remittances sent home by a growing diaspora of emigrants who are motivated by altruism rather than pure self‐interest. Migrants are assumed to care about the consumption of home‐resident family members as well as their own welfare. Hence, remittance effort will depend upon the ratios of per capita income and income growth rates between the host country and the home country. Effort will depend also on the number of emigrants sending back remittances to each home‐resident household. In general, the effect of remittances is to sustain growth of consumption per capita in the home country above the growth rate of per capita GDP. A priori, there is no necessary tendency for remittance effort to rise or fall over time. Falling remittance amounts per migrant may occur as the diaspora grows relative to the home population, but should not be treated as evidence of so‐called ‘remittance fatigue’. A number of feasible scenarios are traced out, and some opportunities are identified to use statistical tests to adjudicate between self‐interest and altruism as motives for sending remittances.     

Genetics of resistance to 3 isolates of Ascochyta fabae on Faba bean (Vicia faba L.) in controlled conditions

Summary Genetics of resistance to Ascochyta fabae Speg. in Vicia faba L. was studied with a final objective to develop resistant faba bean varieties to Ascochyta blight. The study was conducted separately on 3 single spore isolates (AF10-2 and AF13-2 from Tunisia and AF4-3 from France) and belonging to different groups of virulence (GV1 and GV2). Important general combining ability (GCA) effects were found especially with isolates AF10-2 and AF4-3. Specific combining ability (SCA), although significant for the 3 isolates, was important only with AF13 -2, but less important than GCA. Additive gene effects were predominant to non-additive effects. Lines 29H and A8817 transmitted to their progenies resistance to the 3 isolates, whereas 14–12 and 19TB conferred resistance to their progenies only with isolates AF13-2 and AF4-3, respectively. In the material studied, resistance was generally controlled by dominant genes but also could be attributed to recessive genes although less frequent. Analysis of segregation in the F2 of 2 crosses between the resistant lines (A8817 and 29H) and the susceptible line (14–12) with isolate AF4-3 revealed dominant monogenic control at the level of leaves in the 2 resistant lines and, in addition, a recessive gene controlling resistance of stems. Non-allelic interactions were occasionally manifested and their origin appeared to be due to line 19TB. A recurrent selection scheme was proposed with the objective to develop improved open-pollination populations and synthetic varieties responding to the objective of the national Tunisian research programme on faba bean.     

Water for irrigation or hydropower generation?—Complex questions regarding water allocation in Tanzania

The need for achieving efficient, equitable and sustainable use of water resources to meet water demands of different sectors is pressing, particularly in areas where water resources are dwindling. Along with this is the quest for having a good understanding of the value of water in its different uses. Using a simplified model derived from the residual imputation approach (the Change in Net Income Model) we assess the value of water in irrigated paddy and hydropower generation in the Great Ruaha River Catchment (GRRC) in Tanzania. The estimated productivity of water (PW) in irrigated paddy ranges from 0.059 to 0.250 kg/m³ (for withdrawn water) and 0.126 to 0.265 kg/m³ (for consumed water). The PW in hydropower generation is estimated to range from 0.45 to 1.68 kWh/m³. In monetary terms the value of water in irrigated paddy is estimated at 15.3 Tanzanian shilling (Tsh)/m³ (for water withdrawn) and 0.19 Tsh/m³ (for water consumed). The values of water for hydropower generation are relatively higher than for irrigated paddy, ranging from 59 to 226 Tsh/m³. Yet, irrigated paddy also supports livelihoods of about 30,000 agrarian families in the GRRC, with gross revenue of about Tsh 15.9 million per annum and GRCC paddy contributes about 14–24% of national rice production. We conclude that understanding the value of water in its alternative uses is key to fostering informed debate on water management and allocation, identifying the basis for making ‘agreeable’ trade-offs, the potential for improvement and creating linkages with water allocation options particularly in agricultural-based economies, where agriculture competes with other sectors and where water re-allocation decisions may involve large transfers of water from the sector generating the highest pro-poor returns (agriculture for this case) to the sectors generating the highest economic returns (hydropower generation and industrial uses).