Genetics,genomics and breeding of groundnut (Arachis hypogaea L.)

Groundnut is an important food and oil crop in the semiarid tropics, contributing to household food consumption and cash income. In Asia and Africa, yields are low attributed to various production constraints. This review paper highlights advances in genetics, genomics and breeding to improve the productivity of groundnut. Genetic studies concerning inheritance, genetic variability and heritability, combining ability and trait correlations have provided a better understanding of the crop's genetics to develop appropriate breeding strategies for target traits. Several improved lines and sources of variability have been identified or developed for various economically important traits through conventional breeding. Significant advances have also been made in groundnut genomics including genome sequencing, marker development and genetic and trait mapping. These advances have led to a better understanding of the groundnut genome, discovery of genes/variants for traits of interest and integration of marker‐assisted breeding for selected traits. The integration of genomic tools into the breeding process accompanied with increased precision of yield trialing and phenotyping will increase the efficiency and enhance the genetic gain for release of improved groundnut varieties.     

Influence of rate of soil fertilization on alternaria leaf blight (Alternaria dauci) in carrots

The possibility of suppressingAlternaria dauci (Kühn) Groves & Skolko, the causal agent of Alternaria leaf blight in carrot, by excess application of fertilizer was examined in greenhouse and field experiments. Reducing the rate of fertilization by one half from the optimal rate (100 ppm N, 19 ppm P and 74 ppm K) resulted in a 23–30% increase in the severity of Alternaria leaf blight. However, doubling the rate of fertilization resulted in only a 10–15% decrease in disease severity. Inoculating with different concentrations ofA. dauci spores (10³ or 10⁴ spores/ml) did not alter the response of the plants to the fertilization rate, although significantly higher disease severity was observed in plants inoculated with the higher spore concentration. These results were corroborated in the field, where neither disease severity nor harvested yield was significantly affected by tripling the amount of soil fertilization. Application of foliar fungicides, on the other hand, had substantial effects on both disease and yield. Therefore, it was concluded that carrot crops should be fertilized and maintained for optimum yield, and thatA. dauci should be managed by properly timed applications of fungicides during the growing season. Contribution no. 533/99 from the Inst. of Plant Protection, Agricultural Research Organization.     

An ATP gate controls tubulin binding by the tethered head of kinesin-1

Kinesin-1 is a two-headed molecular motor that walks along microtubules, with each step gated by adenosine triphosphate (ATP) binding. Existing models for the gating mechanism propose a role for the microtubule lattice. We show that unpolymerized tubulin binds to kinesin-1, causing tubulin-activated release of adenosine diphosphate (ADP). With no added nucleotide, each kinesin-1 dimer binds one tubulin heterodimer. In adenylyl-imidodiphosphate (AMP-PNP), a nonhydrolyzable ATP analog, each kinesin-1 dimer binds two tubulin heterodimers. The data reveal an ATP gate that operates independently of the microtubule lattice, by ATP-dependent release of a steric or allosteric block on the tubulin binding site of the tethered kinesin-ADP head.     

Genetic mapping of Ir locus in man: linkage to second locus of HL-A

Fifty-seven members of a family that spanned three generations were studied for antigen E and ragweed skin sensitivity and HL-A antigens. There was significant association between the haplotype HL-A 2-12 and antigen E skin hypersensitivity (F = .22 to .26) in this family. The map order is first locus of HL-A, second locus of HL-A, and IrE. These determinants are considered to be part of the linkage group HL-1.     

Biological control of weeds using plant pathogens: accomplishments and limitations

The science and technology of weed control by using plant pathogens gained attention and momentum in the 1970s when some century-old concepts in weed biocontrol and plant disease epidemiology were successfully put to test and a few economically important weeds were controlled by two different strategies. Since then, researchers in different parts of the world have critically examined and tried to apply these strategies with the hope of solving some of the most intractable weed problems. Depending on one"s point of view, this biological control approach has been quite successful or wrought with limitations. In this paper, we describe some of the accomplishments as well as the limitations in this field.     

The contribution of cooperative irrigation scheme to poverty reduction in Tanzania

Irrigation system is a scare resource in most of drought-stricken Africa. How to manage and maintain the existing irrigation facilities in Africa is a debatable issue to both policy makers and beneficiaries. Irrigation facilities run by farmer cooperatives are considered ineffective, unsuccessful and dysfunctional in Tanzania by many researchers. A cooperative irrigation scheme is a mechanism that features the collective management of rural irrigation facilities by farmers' cooperative with some government intervention and external support. There is an increasing emphasis on the roles of cooperative irrigation scheme in the development of the agriculture sector and poverty reduction of smallholder farmers. In this study, the authors investigated the management and services of this scheme and analyzed its contribution to poverty reduction of smallholder rice farmers and community development in Tanzania through both quantitative and qualitative methods. The results showed that the scheme helped smallholder farmers increase the rice production and brought better market opportunities. The farmers' net income was also increased. Profit generated from rice farming not only improved the livelihoods of smallholder farmers but also created more employment opportunities in the rural communities. The research also revealed that the scheme was faced with a number of challenges due to resource and institutional constraints and low-level human capacity for both management and members. The research provides a feasible approach to effective management of small-scale agricultural infrastructure for poverty reduction in Africa.     

Anomalous bottom water South of the grand banks suggests turbidity current activity

Highly turbid bottom water at the margin of the Sohm Abyssal Plain was identified by its temperature, salinity, and oxygen content as originating upslope on the continental rise. The fact that the particulate concentrations were one to two orders of magnitude higher than are normally found in deep ocean waters suggests a turbidity current as the agent bringing this water downslope.