الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
This study was conducted with the goal of exploring the efficacy of abiotic and biotic inducer resistance of Bacillus pumilus (B.p.), Pseudomonas fluorescence (P.f.), Indole Acetic Acid (IAA), Acetyl Salicylic Acid (ASA), Gebrelline (Gb) and Folic Acid (Fo), in sensitive cultivars of cucumber plants and their role of controlling root-knot nematode (Mi) infection.
The primary step in this course of study was initiated with evaluating seven cucumber cultivars against Mi infection to detect the most sensitive involved cultivars.
The screening test on cucumber cultivars (namely, Prince, Lama, Hisham, Madinah, Dahab, Blue master and Tifa), found that, cv. Madinah and cv. Dahab were the most sensitive cultivars wich supported a high population of Mi. Others were hypersensitive or resistant cultivars and therefore, were excluded from the current study.
An extension study was conducted to determine the effects of different concentration of the four abiotic inducer agents on Mi infection and cucumber growth consequently. The results indicated that, abiotic inducers of ASA and IAA were highly effective at concentration of 5000 ppm, while the depressive properties of others, i.e, Gb and Fo, were comparatively low. The reduction of nematode population and other nematode parameters were affected in a corresponding more growth of both tested cultivars. The other concentrations were less functional. However, this trail indicated that both of ASA and IAA were approximately alike in their effectiveness in infected cv. Madinah and cv. Dahab with Mi and a desirable plant growth was obtained.
A subsequent study was sat up to define possible effect of biotic inducer agents, v.z., P.f. and B.p. on infected cv. Madinah and cv. Dahab with Mi. The results revealed that, the standard concentration (108 CFU/ ml.) of B.p. or P.f. were the most effective agents on Mi parameters, i.e., the number of galls, egg masses, emerged IJ2s, immature nematode stages in roots and rate of reproductions. Furthermore, a significant improvement in all vegetative growth criteria, i.e., number of leaves, shoot length, shoot fresh and dry weights, root weight and total fresh weight, were obtained over the other concentrations.
The results confirmed that, both induced cultivars cv. Madinah and cv. Dahab were approximately alike in their response to the tested abiotic (ASA and IAA) or biotic (B.p. and P.f.) agents. Therefore, the following study was done specifically on cucumber cv. Madinah only.
An extensive stage of study was advanced using cv. Madinah to realize the best effective mixture of abiotic and biotic inducer agents on cv. Madinah under Mi infection. In this contention, it realized that combinations containing ”IAA before P.f. by 3 days” or ”ASA before P.f. by 3 days” and then inoculation of Mi after 3 days, resulted in the most highly total fresh weights, shoot fresh and dry weights and shoot length rather than in the other double or single treatments by each agent. Moreover, both of these double combinations provided the highest fruit weights in the tested cv. Madinah.
In regard to the effect of B.p. mixed with ASA or IAA on Mi infection cv. Madinah, the results indicated that, the two combinations which comprised ” IAA before B.p. by 3 days” or ”ASA before B.p. by 3 days” and then Mi inoculation by 3 days, had, on the whole, very drastic influence on Mi final population densities. In the meantime, it was observed an improvement in all vegetative growth criteria compared with the other combinations as well as their respective controls. In addition, there was a significant increase in fruit weights followed by the other treatments.
In the former results, it seems that, time of addition of induced agents appears grossly to be a significant factor for the success or failure of nematode control. Therefore, each abiotic agent must be timed to coincide with occurrence of biotic agents to provide a profitable integral combination. Reasonably, it is apt to conclude in the present study that, the success of these integral combinations of abiotic and biotic agents is time dependent to control Mi infection.
In order to understand the nature of abiotic (ASA and IAA) and biotic (B.p. and P.f.) inducer activities, chemical assessments of induced cv. Madinah were achieved to evaluate the role of these agents to induce plant resistance against Mi infection. The results revealed that, the double combinations of IAA before B.p. by 3 days as well as ASA before B.p. by 3 days, showed the best treatments among all the sole or the other combinations to increase plant resistance against Mi and improved plant vigor. The assessment of both treatments proved an increase in peroxidase activities, proline amino acid and total phenol contents due to application of investigated inducers. Seemingly, the over increase of these biochemical materials may be regarded as one of the manifestations of protective resistance in treated plants against nematodes.
After understanding of mechanisms engaged in increasing resistance to nematode and its effect on the plant growth, the study was directed to investigate the influences of environmental factors that could affect plant resistance to Mi such as the soil types, the application types, and the densities of initial nematode population levels. These studies were conducted using the above tested double combinations of ASA before B.p. by 3 days and then Mi inoculum after 3 days later in cv. Madinah.
As with nematode parameter response in different soil types, the results indicated that, the double combination treatments in clay soil showed the lowest nematode parameters while the sandy soil showed the highest number of final nematode population. Meanwhile, the sandy-clay soil produced a variety of comparative effects on nematode parameters. On the other hand, the results demonstrated that, the highly plant improvement was associated with clay soil and the lowest improvement in plant growth was obtained in sandy soil. In sandy-clay soil, plant growth parameters were modestly affected by nematode infection. Dissimilar to the former trend of plant response, the evaluated crop weight was higher in sandy-clay soil followed by the clay soil and lowered seriously in sandy soil.
The response of induced plants showed great variability between employing different application methods. Generally, the efficacy of application methods on nematode suppression could be arranged in a descending sequence: drench soil, foliar spray then soaking roots. In the meantime, the effectiveness of application methods on plant response was arranged in a descending order: foliar spray, drench soil and then soaking roots. Similar trend was observed on harvested yield.
As with the infection rate of Mi was concerned along with induced combined agents, the results pointed that, 500 and 1000 IJ2s/plant gave a significant success in nematode control, plant growth and yield, while, inoculum level of 2000 IJ2s/plant provided less comparative effect on nematode control, plant growth and harvested yield. Therefore, it was suspected that, a highly tolerated induced plants would realize at 1500 IJ2s/ plant inoculum level.
It is finally stressed in this investigation that; such integral combinations of abiotic and biotic inducer agents could be of a considerable merit in the area of ecofriendly integrated programs of nematode control.