h. r. zamanizadeh

Root knot nematodes (Meloidogyne spp.) are one of the most important plant parasitic nematodes that cause damage to most agricultural crops. In this study, the effect of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae on root knot nematode M. incognita on two cucumber cultivars; tolerant and susceptible was investigated. This experiment was conducted in a completely randomized design with four treatments and four replications. The results showed that adding mycorrhizal fungus one month before inoculation of nematode caused a significant decrease in nematode pathogenicity factors (number of galls, number of eggs, eggs per egg mass and number of second stage juveniles) in both tolerant and susceptible cultivars (cv). Although the pathogenicity of the nematode in tolerant cultivars was lower than that of susceptible cvs, inoculation of susceptible roots with mycorrhizal fungus significantly reduced the pathogenicity of the nematode. The reproductive factor decreased in mycorrhizal plants in tolerant and susceptible cultivars in 50 and 66.6%, respectively. The presence of mycorrhizal in tolerant and sensitive cultivar reduced 64 and 63.3% of the second larval population in the soil, respectively. Also, the comparison of the mean number, size and area of giant cells and the number and diameter of the nucleus in 2 cvs showed a significant difference between the plants with or without mycorrhizal fungus. Since mycorrhizal fungus reduces the pathogenicity of the root knot nematode and increases the resistance of the cv susceptible to nematode, it can be considered as an option for biologic control of the root knot nematode.

Nevertheless, Septoria leaf blotch disease management relies mainly on successful strategies of breeding for resistance which depends on primary data of pathotype of the pathogen population and their virulence in infected areas. In this research, 23 strains were individually inoculated on 19 differential wheat cultivars in seedling stage under greenhouse condition and pathotype determined. Results showed that differences due to cultivars and isolates were highly significant at 1 levels.The cultivar x isolate interaction component was relatively very small and not significant that showed isolates would thus not vary in aggressiveness and cultivars in race- nonspecific resistance. None of the isolates had virulence on cultivar TE 9111 carrying Stb6, Stb7 and Stb11. Since the virulence was observed on some cultivars carrying Stb6 and/or Stb7 by specific isolates, then the resistance of TE 9111 can be attributed to Stb11. Maximum and minimum frequency of virulence were observed on Boolani (general susceptible control), Taichung 29 (international control, susceptible to the standard isolate IPO323) by 69% and Estanzuela Federal (carrying St 7) by 66%, and on TE9111 (carrying Stb4 and Stb6) by 4% and Oasis and Sulivan (carrying Stb1) by 9% and 11% respectively. Virulence frequency of isolates on other wheat cultivars carrying different Stb genes was varied between 16 to 59%. Three isolates proved to be one pathotype by showing the same virulence pattern on Stb genes, whereas other isolates showed different virulence patterns on wheat differential cultivars. This study identified 18 M. graminicola pathotypes which shows a high genetic diversity among the Iranian pathogen populations.

Thirteen strains of Streptomyces were evaluated as a potential biological agent for control of cantaloup mot rot that caused by P. drechsleri. Eight strains of Streptomyces were obtained from soil surrounding the roots of cucurbit plants in Varamin area and five strains were obtained from soil surronding roots of capsicum in glasshouse. Dual culture and cellophane overlay technique were used for in vitro assay. In dual culture and cellophane overlay techniques, all strains of Streptomyces inhibited the growth of P. drechsleri. The inhibition rate varied among strains of Streptomyces and ranged from 33.01% to 93.07% in dual culture and frol1'l36.18% to 100% in the cellophane overlay method. Adding a mixture of 13Streptomyces strains (5 g) prepared in 1 kg wheat bran to soil infested with mixture of six P. drechsleri isolates increased seedling survival by 43.07% (P < 0.05). Also seed treatment with 7.3 x 106 cfu per seed increased plant stand by 50.21% (P < 0.01). Average population of Streptomyces in potting mix decreased at a uniform rate.