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Drought is the major constraint to chickpea (Cicer arietinum L.) productivity worldwide. Utilizing early-flowering genotypes and advancing sowing from spring to autumn have been suggested as strategies for drought avoidance. However, Ascochyta blight (causal agent: Didymella rabiei (Kov.) v. Arx.) is a major limitation for chickpea winter cultivation. Most efforts to introgress resistance to the pathogen into Kabuli germplasm resulted in relatively late flowering germplasm. With the aim to explore the feasibility of combining earliness and resistance, RILs derived from a cross between a Kabuli cultivar and a Desi accession were evaluated under field conditions and genotyped with SSR markers. Three quantitative trait loci (QTLs) with significant effects on resistance were identified: two linked loci located on LG4 in epistatic interaction and a third locus on LG8. Two QTLs were detected for time to flowering: one in LG1 and another on LG2. When resistance and time to flowering were analyzed together, the significance of the resistance estimates obtained for the LG8 locus increased and the locus effect on days to flowering, previously undetected, was significantly different from zero. The identification of a locus linked both to resistance and time to flowering may account for the correlation observed between these traits in this and other breeding attempts.

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Yields of dryland crops in semiarid and arid zones are limited by precipitation, and so water content and placement are very important at each stage of development. Spring wheat (Triticum ai!Stivum L.) grown in a wheat-fallow (WF) rotation system (1 crop in 2 years) generally occupies the greatest area in the Israeli dryland region, more than the continuous wheat (CW) rotation system. To identify the optimal crop management for dry land farming where annual precipitation is <250 mm, we compared the effects of no-tillage (NT) and conventional tillage (CT) on wheat growth and water use efficiency (WUE) in both the WF and the CW rotation systems, and on water storage in fallow (F) plots. During the 4-year period from 1994 to 1997, experiments were conducted at Gilat Experimental Station, located in the south of Israel (average annual precipitation, 237 mm; soil type, sandy loam loess-Calcic Xerosol). In the fallow year, F-NT increased water infiltration and soil water content in comparison with F-CT. However, most of the water evaporated during the summer, especially from the upper soil layer (0-120 em). During growth, uncultivated soil with straw mulch increased water content in the upper soil layer and also encouraged the development of a longer root system capable of utilizing deeper water. During 1995, similar grain yields were obtained with both NT and CT treatments, an average of 3.45 t ha-1 for WF and 2.9 t ha-1 for CW. In the last 2 drought years (1996 and 1997), NT management increased yields by 62 to 67% for WF and by 18 to 75% for CW, relative to CT management. During the 2 years when water deficiency occurred during the grain-filling stage (1994 and 1997), NT management increased grain weight by 20% and test weight by 5 to 7%, in addition to the 70 to 200% increase in the total grain yield, relative to CT management. Crop yield and WUE can be increased in arid zones with annual precipitation of <200 mm, through use of a wheat-fallow rotation system that is managed by NT.

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Cyanobacteria possess an inducible mechanism which enables them to concentrate inorganic carbon (Ci) within the cells. An inactivation library was used to raise the high-CO Prequiring mutant of Synechococcus PCC 7942, IL-2, impaired in rgy 3 3 transport. Analysis of the relevant genomic DNA detected several modifications, probably due to the single crossover recombination, leading to inactivation of ORF467 (designated ictB) in IL-2. IctB contains 10 trans-membrane regions and is homologous to several transport-related proteins from various organisms. Kinetic analyses of rgy 3 3 uptake in the wild type and IL-2 suggested the presence of two or three rgy 3 3 carriers exhibiting different affinities to rgy 3 3 . z 1998 Federation of European Biochemical Societies.