Rhizoctonia solani anastomosis group 4 (AG-4) is a serious pathogen causing damping off and root rot in many important crop plants. A total of 190 isolates of R. solani AG-4 HG-I were collected from host fields in five provinces of Iran. The genetic structure of this pathogen was evaluated using seven microsatellite loci, focusing particularly on geographic differentiation. Most of the multilocus genotypes (MLGTs) were unique, with few MLGTs shared among populations. High to moderate levels of gene flow among populations was indicated by low to moderate differentiation between pairs of populations based on the fixation index (F ST ). Gametic equilibrium of most pairs of microsatellite loci and moderate genotypic diversity were found for two out of five populations, indicating that these populations were sexually recombining in structure. High genotypic diversity, moderate clonal fractions and site-specific genotypes were consistent with mixed reproductive systems for the remaining populations. The findings of departures from Hardy-Weinberg (HW) equilibrium, gametic disequilibrium and a significant excess of homozygotes in half or more than half of the loci were probably caused by the presence of null alleles and the Wahlund effect. This is the first study to consider the population genetics of the root and crown rot pathogen R. solani AG-4.

The most important step in developing of a sugar beet hybrid for target trait is selection of CMS line or single cross. In the present study, 12 progenies derived of 4 sugar beet lines(as female parent) with different level of rhizomania resistant, along with 3 pollinators 27270, 27273 and 27274(as male parent) and parents were evaluated in two locations (Mashhad and Shiraz) with rhizomania infestation in 5×5 latice design with 4 replications. The traits consisted of: Root yield (RY), sugar yield (SY), sugar content (SC), Na, K, N- , white sugar content (WSC), purity (PUR) and molas percent (MS). The data analyzed as factorial model in randomized complete block design. The results of genetic analyses in two locations showed significant differences among parents for all the traits except for K and N-. Variance of hybrid was significant for RY and SY. In Mashhad experiment L3 line and T3 pollinator and in Shiraz experiment L3 and L1 lines and T3 pollinator were selected as superior parents for RY, SY and N- traits. The value of SCA showed that in Mashhad experiment L1×T3, L2×T2, L3×T1 and L4×T1 crosses and in Shiraz experiment L1×T1, L2×T3 and L1×T3 had significant and positive value of SCA for RY and SY. As a total, the results showed that cross between a rhizomania susceptible single cross (L1) with a resistant pollinator (T3) was the best sugar beet hybrid among them.