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MANAGEMENT OF PLANT PARASITIC NEMATODES ASSOCIATED WITH DATE-PALM (PHOENIX DACTYLIFERA L) USING COMMON PLANTS

Islam, shamsul (2008) MANAGEMENT OF PLANT PARASITIC NEMATODES ASSOCIATED WITH DATE-PALM (PHOENIX DACTYLIFERA L) USING COMMON PLANTS. PhD thesis, University of Karachi, Karachi.

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Abstract

The date-palm fruit is also known as "heavenly fruit" because of its mention in religious scriptures. It contains rich carbohydrates, vitamin B and D, potassium, calcium, iron and other tonic ingredients. Pakistan is ranked among the 5th leading producers of dates after Iraq, Egypt, Saudi Arabia and Iran. The date-palm trees are infested by a number of pathogens including nematodes which eventually reduce its yield. During July 2001 to June 2004 a total of seven nematode genera were recorded from Khuzdar district that included Tylenchus sp. Bastian, 1865; Merlinius khuzdarensis n.sp.: M. brevidens (Allen, 1955) Siddiqi, 1970; Helicotylenchus indicus Sher, 1963; Psilenchus hilarulus Siddiqi, 1963; Xiphinema americanum Cobb, 1913; Aphelenchoides sp. Fischer, 1894 and Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949. The similarity between localities based on the qualitative (presence / absence) nematode data was calculated on the basis of Jaccard's coefficient of similarity. Group structure inherent in the data sets relevant to Khuzdar localities were exposed using average linkage clustering strategy. An identification key to 32 valid species of stunt nematodes (Merlinius spp.) is given. A compendium of the most important diagnostic characters for use in identification of species is included as a practical alternative and supplement to the key. The diagnosis of Merlinius is emended, and a list of all the valid species of the genus is given. The characters most useful for separating species include body and stylet lengths, shape of head, tail and tail terminus, number of head and tail annules, position of vulva (V), and c' ratio in females. Also useful are length and shape of spicules and gubernacula in males. A new stunt nematode. Merlinius khuzdarensis n.sp., is described, photographed and illustrated and was found around the soil and roots of date-palm (Phoenix dactylifera L.) from Khuzdar, Balochistan Province, Pakistan. This new species resembles M bavaricus. M communicus. M bilqeesae and M montanus, but differs from these species by the following: body and stylet length, shape of head, tail and tail terminus, number of head and tail annules, position of phasmids and by their vastly different habitat. Because this species is limited in distribution, its economic importance in date-palm and other cultivated crops within the region is not known. From March 2002 to February 2003 the affect of marigold (Tagetes erecta L.) flowers leaves. seeds and the nematicide Carbofuran was investigated on the population dynamics of Xiphinema americanum, Merlinius brevidens, Meloidogyne species larvae and Psilenchus hilarulus associated with date-palm at Kaley Haji Mohd. Malik farm, Khuzdar, Balochistan. Population of Xiphinema americanum was abated most by marigold leaves followed by Carbofuran, marigold flowers and mustard seeds; M brevidens population was reduced most by marigold leaves followed by Carbofuran, marigold seeds and marigold flowers, Meloidogyne sp. larvae population was depleted most by marigold leaves and Carbofuran while P. hilarulus population was reduced most by marigold leaves. Marigold produces no toxic residues in soil and can provide an alternate means for replacing the chemical nematicides. The influence of soil amendment with four plant species including Lantana camara, Mirabilis jalapa, Catharanthus roseus and Oscimum basilicum, and a conventional nematicide carbofuran was tested on population dynamics of three plant parasitic nematode species such as Xiphinema americanum, Merlinius sp. and Helicotylenchus indicus in the rhizospheres of date-palm at Kararo, District Khuzdar, Balochistan. A field experiment was established during August 2003-August 2004 in a randomized complete block design and soil was sampled at 0, 3, 6, 9 and 12 month intervals after amendment. Treatment with chopped leaves of plant species differentially influenced nematode population densities. Likewise, treatments influenced nematode populations differently at different sampling period. Carbofuran was found to be the most effective treatment in reducing populations of all the nematode species. When plant species were compared for nematicidal potential, populations of X americanum was reduced most following soil amendment with O. basilicum while those of Merlinius sp. and H. indicus by L. camara. Regardless of the treatment, rhizospheres of date-palm harboured highest populations of X americanum followed by H. indicus and Merlinius sp. Soil amendment with L. camara also significantly enhanced yield of date followed by O. basilicum. Besides common plants thirty-seven isolates representing fluorescent pseudomonads (Pseudomonas aeruginosa, 6 isolates and Pseudomonas sp. 31 isolates) were collected from the rhizosphere of field-grown date-palm. Coconut palm, okra and brinjal plants to select candidate strains for biological control of plant-parasitic nematodes including Helicotylenchus indicus, Xiphinema americanum and Meloidogyne incognita. Among all the isolates tested under in vitro conditions, 26 produced siderophores, 14 produced salicylic acid, 7 produced 2,4-diacetylphloroglucinol, 6 synthesized cyanide and 12 produced extracellular proteases. Twenty-four isolates applied as seed treatment enhanced fresh shoot weight of mungbean in unsterilised sandy loam soil. Bacterial isolates showed marked differences in their activity towards plant-parasitic nematodes in vitro. Apart from DAPG, which was exclusively biosynthesized by the isolates of Pseudomonas sp., none of the secondary metabolite was species-specific. Of the 30 isolates tested for activity against X americanum, culture filtrates of only 2 isolates caused more than 50% mortality of the juveniles. Four out of 25 isolates tested resulted in more than 50% mortality of the juveniles of H indicus while, 4 out of 27 isolates gave more than 50 % mortality of the juveniles of M incognita. Among all the isolates tested, only two exhibited more than 50% mortality of the juveniles of all three nematode species. Using a cluster strategy, the bacterial isolates formed 4 major groups depending upon potential to produce biochemicals, promote mungbean plant growth and nematicidal activity. The first group comprised of five (CD 63, CD 62, CD 38, CD 36 and CD 28) isolates that exhibited active metabolic activity, producing all or almost all the tested biochemicals, and had high nematicidal activity. These isolates seem to have potential to produce as biocontrol agent for effective nematode control. Under glasshouse conditions, in the repeated trials, seed bacterization with isolates CD 38 and CD 62 did suppress galling due to M incognita and nematode densities in mungbean roots while secondary metabolites and protease-negative isolate CD 22 did not. None of the isolates were able to reduce nematode reproductive potential (as determined by egg production) were not significantly different from non-bacterized controls. The isolates, which reduced nematode populations and root-knot disease, also enhanced fresh weights of shoots but not that of roots. Isolates CD 38 and CD 62 attained a mean population of 105 cfu (per g fresh weight of roots) in mungbean rhizosphere while final population density of CD 22 in the rhizosphere was 104 cfu.

Item Type:Thesis (PhD)
Uncontrolled Keywords:plant parasitic nematodes, date-palm, phoenix dactylifera l, merlinius siddiqi, marigold, fluorescent pseudomonads
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Zoological sciences(c1.11)
ID Code:2699
Deposited By:Mr. Javed Memon
Deposited On:03 Sep 2009 14:11
Last Modified:03 Sep 2009 14:11

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