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The availability of more resistance genes to Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) may provide additional protection from new virulent strains or biotypes of the insect. This genetic study was conducted to determine the allelic relationships of resistance genes in two Iranian wheat (Triticum aestivum L.) lines, SHZ.W.102 and SHZ.W.104 and lines PI 137739, PI 262660, PI 372129, PI 294994 and PI 243781, carrying resistance genes Dn1, Dn2, Dn4, Dn5 and Dn6 respectively. The two Iranian lines were crossed to each of the other resistant lines, and F1 and F2 seedlings were screened for RWA reaction. The resistance gene in 102 was allelic to Dn1, however, the resistance gene in 104 was different from other known genes. The resistant line 104 is an effective source of genetic resistance to RWA and the gene symbol Dn7 is proposed for its resistance gene.

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<p class="042abstractstekst">Sorghum (<em>Sorghum bicolor</em> (L.) Moench) is the fifth important cereal considered a drought-tolerant crop. However, its reduction of grain yield considerably occurs in a shortage of water. In the current study, 10 sorghum genotypes were assessed for their grain yield under normal irrigation and water deficit irrigation. As well, the efficacy of several drought indices was evaluated for the selection of high-yield and drought-tolerant genotypes. The experiment was conducted as a split-plot considering three irrigation levels as main-plot and 10 genotypes as sub-plot. Correlation among the indices, clustering of the genotypes along with principal component analysis was employed. Yield production was significantly and positively correlated with indices MP (mean productivity), STI (stress tolerance index), GMP (geometric productivity), HM (harmonic mean), and YI (yield index) in all the irrigation levels. Therefore, these indices are more effective in the selection of high-yielding genotypes under different water conditions. Rank means of stress indices for each genotype revealed that genotype TN-04-79 in mild deficit irrigation and genotypes KGS23 and TN-04-79 in severe deficit irrigation were the most tolerant.</p>

Maize rough dwarf virus (MRDV) is the most important disease affecting maize growth in Iran. In the present study, the putative resistance capacity of 35 maize inbred lines against the causal agents of MRDVwas studied under natural field infection in 2010 and 2011. The viral transmitter was a plant hopper known as Laodelphax steriatellus. Early sowing provided suitable temperatures for vector propagation and transmission and therefore natural infection under field conditions. Sowing single rows of SC704 as vector spreader between every five rows of inbred lines caused adequate vector propagation and viral transmission. This shows that viral infection was sufficient and possible resistance was linked to viral resistance, not failure, in vector transmission. In principal component biplot, plant height vector had wide angles with the vectors for disease severity index and MRDV incidence that showed the negative association of plant height with MRDV disease. The percentage of natural infection to MRDV in susceptible control(SC704) was about 64%. The genotypes A679, K3547/3, K3545/6, K3653/2, and B84 were more susceptible to MRDV. Only the line K3640/3 had low disease incidence and severity and it can be considered as resistant for possible use in genetic studies. Results showed that an early sowing of maize in temperate regions increases the chance of transmitting viruses via their vector.