سبب شناسي پوسيدگي غده هاي سيب زميني در منطقه دامنه اصفهان

چكيده انگليسي :

Abstract Potato tuber rot is a common and important disease in the world that has been recently occurred in potatofields of Damaneh in Isfahan province Skins of the infected tubers are usually cracked and darken cavitiescontaining nematodes are observed in the tuber flesh In some cases affected tubers had soft rot symptomswith brown margins as described for pectolytic bacteria To identify the pathogens involved in thedevelopment and spread of potato tubers rot in the region a large number of rotten potatoes were collectedfrom the potato fields of Damaneh between 2009 and 2010 Microscopic examination of the cracked skintubers showed the presence of many nematodes in white pockets of flesh of these samples The majority ofnematodes found in the pockets were identified as Ditylenchus destructor based on morphological andmorphometric characters PCR tests using general primer rDNA1 rDNA2 yielded a DNA fragment lengthapproximately 950bp corresponded to ITS region of the nematode samples The TaqI digestion of 950 bpfragment revealed the genetic homology among ITS region of the strains of D destructor collected fromDamaneh Sequence analysis of this fragment and its alignment with the sequences deposited in NCBIdatabase indicated that the ITS sequences of the nematode causes potato tuber rot in Isfahan has significanthomology 99 97 with the sequence of D destructor isolates reported from various countries Fifteenpectolytic bacteria with green metallic colonies on EMB medium were isolated from the tubers showingsurface cracking and soft rot symptoms simultaneously All the isolates grew at 36 C were resistant toerythromycin negative for phosphatase indole production production of reducing substances from sucrose xylose trehalose methyl D glycoside palatinose and malonate while positive for acid production frominositol ramnose and arabitol Based on These characteristics the isolates recognized as P carotovorumsubsp carotovorum The isolates were further identified by PCR amplification with primer G1 L1 whichproduces two bands similar to those produced in P carotovorum subsp carotovorum but not from P carotovorum subsp atrosepticum and Dickeya chrysanthemi Digestion of the amplified PCR product withrestriction enzyme Rsa I resulted in identical bands formation as described for P carotovorum subsp carotovorum The results of physiological pathogenicity biochemical and molecular tests confirmed that allbacterial isolates induced soft rot symptoms in potato tubers are P carotovorum subsp carotovorum Todetermine the role of each pathogen in occurrence of potato tuber rot complex an appropriate amount of D destructor and P carotovorum subsp carotovorum were inoculated alone and together in potato plants grownin greenhouse conditions Tuber rot symptoms identical to those observed in the field appeared on all tubersinoculated with D destructor but not on the P carotovorum subsp carotovorum inoculated tubers Co inoculation of P carotovorum subsp carotovorum with D destructor resulted the tubers with surface skincracking symptoms and soft rot symptoms simultaneously Based on these results it could be concluded thatthe nematode D destructor alone could be the main causal agent of potato tuber rot in Damaneh and possiblyP carotovorum subsp carotovorum penetrates and cause soft rot in the tissues through wounds created bynematodes Knowing alternate crop or weed hosts of D destructor in the region and determination theinfluence of crop rotation to reduce disease incidence will be helpful to manage the disease losses in theregion Key words Potato tuber rot Pectobacterium carotovorum subsp carotovorum Ditylenchus destructor

شكيبا فرد، طاهره

سبب شناسي پوسيدگي غده هاي سيب زميني در منطقه دامنه اصفهان

ِDitylenchus destructor