فهرست مطالب m.a. malboobi

Fusarium wilt disease is one of the most important diseases of melon, which causes damage between 20 and 80% in melon fields. In favorable conditions, the spread of the disease can reach 100%. In the improvement programs, achieving resistant cultivars is considered one of the most important methods of controlling this disease.

In this research, 46 melon landraces were collected from different parts of Razavi, Northern and Southern Khorasan provinces, along with two separate lines, Isabel and Charente T respectively as resistant and sensitive control cultivars to identify new sources of wilt disease resistance to Fusarium oxysporum f. sp. melonis. The experiments were carried out in a randomized complete block design with three replications in the greenhouse of the agricultural campus of Tarbiat Modares University. The seeds were grown in trays containing cocopeat and perlite in a ratio of 2:1; fourteen days after cultivation, the roots of the young seedlings were removed from the culture tray and inoculated for two minutes with the isolate Mt13-3a of F. oxysporum f. sp. melonis race 1.2 spore suspension solution, with a concentration of 106 conidium per milliliter. The symptom was evaluated nine days after inoculation. The spread of symptoms on the plants was recorded every day for 30 days until the complete death of the plant. Evaluation of resistance was calculated using the indices of the area under the disease progress curve (AUDPC), latent period (LP), disease severity index (DSI), and standardized area under the disease progress curve (SAUDPC) in landraces. Investigating the variation of the resistance of the studied landraces based on the mentioned indices was done using analysis of variance and cluster analysis.

The results of the analysis of variance of the data indicated the existence of a significant difference of 1% between the landraces for all four studied indices. Based on the heat map results, there is resistance to race 1.2 of F. oxysporum f. sp. melonis in the genotype Isabel and Tude Qaenat. Also, the cluster analysis of landraces based on Ward's method led to identifying six resistance groups from the 46 landraces studied, along with two differential control lines.

The results of the present research showed that for all four indices of LP, AUDPC, DSI and SAUDPC, there is resistance to race 1.2 of F. oxysporum f. sp. melonis in Isabel genotype as a resistant control and the landraces of Qaenat, Till Magasi, Till Zard, Till Torgh, Laki 1 and Till Keshideh compared to the sensitive control (Charente T).

Phosphorus (P) is one of three essential macronutrients required for plants which is absorbed as phosphate ion (Pi) from the soil solution and plays an important role in plants growth and development. To cope with low Pi concentrations in soil, plants have a wide range of morphological and physiological adaptive responses including acid phosphatase secretion. In this study, the full-length cDNA encoding sequence of AtPAP18 was isolated from a cDNA pool of Arabidopsis and cloned in a plant expression vector to produce a series of overexpressed lines. Also, a homozygous knocked-out mutant was identified for disruption in AtPAP18 locus too. Our results indicated that the overexpression of AtPAP18 in Arabidopsis plants led to significant increases in total P contents and biomass production for plants grown in Pi-fed and starved conditions. Faster germination, remarkable decrease in fresh and dry weight of and the highest root–shoot ratio in the starved plants was the obvious symptoms of the knocked out plants in comparison to wild type or overexpressed ones. The results indicated that overexpression of the AtPAP18 gene offers an effective way to increase the utilization of soil insoluble Pi and reduce the consumption of the relevant chemical fertilizer.

OF2 and VAP genes, probably involved in signal transduction of sugarbeet nematode resistance, have already been cloned in bacterial vector by AFLP molecular marker and a two-hybrid system, respectively. To examine their capability to introduce resistance in sugarbeet, the genes were transferred to plant expression vectors. For this reason, OF2 gene after isolation was inserted within T-DNA of pAM194 binary vector, downstream of CaMV35S constitutive promoter and also inserted within T-DNA of modified pBin121 binary vector, downstream of HS1pro-1 gene inducing promoter (responsible for nematode resistance). VAP gene after isolation was inserted within T-DNA of pAM194 plasmid, downstream of CaMV35S constitutive promoter. Thus, three new constructs were made in which genes of signal transduction pathway were expressed to give beet cyst nematode resistance. These plasmids were separately transferred to Agrobacterium rhizogenes, strain AR15834. In the next step, petiole explants of sugarbeet were inoculated with the bacterial cells. Transformation-derived hairy roots were analyzed by GUS staining and/or PCR and were then inoculated with nematode larvae. Primary results showed partial resistance against nematode larvae in some hairy roots. As a result, this resistance can be related to OF2 and VAP genes effect.