Four clonal lineages of Cephalosporium maydis, a soilborne vascular wilt pathogen that causes late wilt of maize, were differentiated previously with molecular markers. In Egypt, this fungus can cause significant losses in infected susceptible plants. In greenhouse tests of individual isolates we found that these lineages differ in their virulence toward a series of maize accessions commonly used in Egyptian maize breeding programs. We also determined the relative competitiveness of representatives of the four lineages when incorporated into the soil as a mixed inoculum. The lineage (IV) with greatest mean disease incidence (virulence), when tested alone, was the least competitive on susceptible maize accessions when coinoculated as a component of mixed inocula of all four lineages. In these coinoculation experiments, one of the less-virulent lineages (II) dominated (70% of infections) and appeared to be the most competitive. These results suggest that virulence and competitive ability are not the same in this host-pathogen system. These results also suggest that standard protocols that rely on mixed inocula for resistance screening need to be altered, and that the relative proportion of the different lineages of the pathogen recovered in a field may be influenced by the maize variety/hybrid planted.

Two cultivars of maize (Zea mays), Giza 2 (G2) and Population 45 (P45), were grown under natural conditions in pots containing clay loam soil, either infested or not infested with inoculum of Cephalosporium maydis, the causal fungus of late wilt disease. When the plants were 21 days old, they were subjected to two irrigation treatments: irrigation to field capacity, and irrigation after 60% depletion of the available soil moisture at the root zone, i.e. soil moisture stress. Under nonstressed conditions plants of cultivar G2 showed a lower percentage of infection than those of P45. In stressed plants, the percentage of infection increased significantly. Compared with controls (nonstressed, healthy plants), higher percentages of plant dry mass (leaves þ stem þ cobs) were achieved by all treatments with G2 than with P45, which did not produce cobs under stress conditions. Nonstressed healthy plants had higher transpiration rates and relative water contents than the water-stressed diseased plants. The leaves of diseased plants had a higher content of the amino acid proline than those of nonstressed, healthy plants, probably associated with water stress due to the disease.Infection resulted in a reduction of the number of the vascular bundles in the cross-section of the internode. The values of the phloem area per unit leaf area were greatly reduced in water-stressed and infected plants. In addition, many xylem vessels were occluded in diseased plants but much more in the susceptible P45 than in the moderately resistant G2. Occlusion may be the most important factor causing the symptoms of the disease.The hydraulic conductance (Kh) of the xylem tissue supplying the transpiring areas was calculated from the conduit lumen diameters using the Hagen-Poiseuille relation. The highest Kh values were obtained in the nonstressed, healthy plants, particularly those of P45; plants with both water stress and disease showed the lowest Kh values. The efficiency of xylem conductance was further examined by calculations of the leaf specific conductance and the predicted maximum pressure gradients. Conductance was strongly reduced by infection in both cultivars and there was a corresponding increase in pressure gradients. These observations were consistent with observed reduction in xylem tissues and occlusion of xylem vessels by the infection.

Cephalosporium maydis, the causal agent of late wilt of maize, was first described in Egypt in the 1960s, where it can cause yield losses of up to 40% in susceptible plantings. We characterized 866 isolates of C. maydis collected from 14 governates in Egypt, 7 in the Nile River Delta and 7 in southern (Middle and Upper) Egypt, with amplified fragment length polymorphism (AFLP) markers. The four AFLP primer-pair combinations generated 68 bands, 25 of which were polymorphic, resulting in 52 clonal haplotypes that clustered the 866 isolates into four phylogenetic lineages. Three lineages were found in both the Nile River Delta and southern Egypt. Lineage IV, the most diverse group (20 haplotypes), was recovered only from governates in the Nile River Delta. In some locations, one lineage dominated (up to 98% of the isolates recovered) and, from some fields, only a single haplotype was recovered. Under field conditions in Egypt, there is no evidence that C. maydis reproduces sexually. The nonuniform geographic distribution of the pathogen lineages within the country could be due to differences in climate or in the farming system, because host material differs in susceptibility and C. maydis lineages differ in pathogenicity.

4-(4-Acetylphenylamino)cycloocteno [4,5]thieno [2,3-d]pyrimidine (4) was prepared and condensed with certain aldehydes, phenylhydrazine, malononitrile to obtain 5a-d, 6 and 7, respectively. 4-Hydrazino & 4-substituted amino derivatives of 2-arylcycloocteno[4,5]thienopyrimidines 10a-c & 11a-i were synthesized. Cyclization of the hydrazino compounds 10a-c with orthoalkanoate esters or the arylidene derivatives 12a-c with bromine in acetic acid afforded the fused triazolo system 13a-i. Reaction of the hydrazino compound 10c with acetic anhydride gave 15 while the reaction of 10b,c with acid chlorides gave 16a-d. Furthermore, the tetrazolothienopyrimidines 17a-c were synthesized. Some of the newly synthesized compounds were tested for their antimicrobial activity.

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