Use of RAPD markers for assessment of genetic diversity in sugarcane cultivars

67-71Random amplified polymorphic DNA (RAPD) analysis was carried out in 17 cultivars of sugarcane. Selected 40 primers generated 325 bands, 134 of which were found to be polymorphic. The number of amplification products ranged from 3 to 15 for different primers. The genetic similarity among sugarcane cultivars ranged from 0.77 to 0.99. The average genetic similarity was 0.87. UPGMA cluster analysis placed these cultivars in to different groups. The parentage of the varieties did not contribute significantly to the grouping pattern. Varieties belonging to the common female parent were under different groups, while varieties from different parentage were under same group. Among the varieties Co SNK 3754 was found to be totally distinct and divergent from rest of the varieties. The study reveals the limited genetic base of the current Indian commercial varieties and the need to diversify the genetic base by using new sources from the germplasm

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Not AvailableFungicides of demethylation inhibitor (DMI) group are used worldwide for the management of Erysiphe necator but are associated with medium to high risk of development of resistance in the pathogen. Till date there was no report on the presence of DMI resistance in E. necator isolates from the major grape growing regions in tropical India, though there were instances of DMI fungicides providing less than accepted levels of powdery mildew control. In this study, 54 E. necator isolates were collected during 2015–2017 from vineyards located in different geographical regions of India. The isolates were tested for their sensitivity to the commonly used DMI fungicide, myclobutanil, using leaf disc bioassay. Four isolates were sensitive (MIC 10 μg/ml) to the fungicide myclobutanil. The resistance factor (RF) ranged from 1.5 to 295. In PCR amplification of a specific allele, the product specific for A495T mutation was produced only in the 43 isolates with RF > 4. The CYP51 gene sequence analysis confirmed A495T mutation leading to Y136F change associated with high levels of resistance to DMI fungicides. Cross resistance studies among the DMI fungicides showed that 11 out of 13 myclobutanil resistant isolates were also resistant to difenoconazole and tetraconazole. Three myclobutanil sensitive isolates were also sensitive to difenoconazole and tetraconazole. Detection of resistance in E. necator isolates from the major grape growing region of tropical India stresses on the need for developing resistance management strategies.Not Availabl

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Not AvailablePowdery mildew causes significant yield and quality loss in grapes. Disease management includes fungicides belonging to the demethylation inhibitor and quinone outside inhibitor groups which are associated with development of fungicide resistant pathogen populations and detection of fungicide residues at harvest. This study was conducted to identify potential antagonists which can be used solo or in integration with safer chemical. Three mycoparasitic fungi were isolated and evaluated for parasitism and biocontrol. Light and scanning electron microscopic analysis showed that the hyphae of mycoparasites grew over the powdery mildew colony forming a mycelial web over it, coiled around the conidiophores and conidia of E. necator, penetrated the conidia and caused their total collapse. Based on molecular identification, the mycoparasites were identified as Lecanicillium antillanum, Acremonium sclerotigenum and Sarocladium terricola. All three isolates were positive for production of β-1-3 glucanase, cellulase, chitinase, protease, amylase and lipase which are involved in bio-control mechanism. During pot, nursery and vineyard trials all the isolates consistently showed powdery mildew reduction and achieved 41.76% to 65.61% disease reduction. Sarocladium terricola was more effective in all the trials. All three mycoparasites were compatible with chitosan and sulfur and alternate applications of mycoparasites with these two safe chemicals, the efficiency of L. antillanum, A. sclerotigenum and S. terricola was increased by 20.16, 27.33, and 8.94%respectively on leaves and 20.85, 21.36, and 16.06% respectively on bunches as compared to their solo applications. The study introduces new possibilities for control of grape powdery mildew using safer alternatives.Not Availabl

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Not AvailableQuinone outside inhibitor (QoI) fungicides are used worldwide for the management of Erysiphe necator but with associated problem of resistance development in the pathogen. Twenty ninr E.necator isolates were collected during 2015-2016 from different geographical regions of India. In leaf disc bioassay using azoxystrobin, the EC50 of four isolates from research farms was <1 ug/ml while 25 isolates from commercial vineyards had produced a 100 bp PCR product with G143A mutant allele specification of cytochrome b gene (Cyt b) and used for amplification of the gene from two resistant and two sensitive isolates. Alignment of amino acid swquences showed that the QoI resistant isolates harboured a G143A mutation, which was absent in the sensitive isolates. The two haplotypes of Cyt b gene from a resistant isolate, SAA2, and a sensitive isolate, HP1, have been deposited in GenBank under accession numbers KY418049 and KY418048, respectively. This is the first report of presence of QoI resistant isolates of E.necator from India. Studies point out the need for developing resistance management strategies by interspersing bio-control ahents with judicious use of fungicides.Not Availabl

RAPD and ISSR fingerprints as useful genetic markers for analysis of genetic diversity, varietal identification, and phylogenetic relationships in peanut (<i>Arachis hypogaea</i>) cultivars and wild species

Twenty-one random and 29 SSR primers were used to assess genetic variation and interrelationships among subspecies and botanical varieties of cultivated peanut, Arachis hypogaea (2n = 4x = 40), and phylogenetic relationships among cultivated peanut and wild species of the genus Arachis. In contrast with the previous generalization that peanut accessions lack genetic variation, both random and SSR primers revealed 42.7 and 54.4% polymorphism, respectively, among 220 and 124 genetic loci amplified from 13 accessions. Moreover, the dendrograms based on RAPD, ISSR, and RAPD + ISSR data precisely organized the five botanical varieties of the two subspecies into five clusters. One SSR primer was identified that could distinguish all the accessions analysed within a variety. Although the polymorphic index content varied from 0.1 to 0.5 for both ISSR and RAPD markers, primer index values were substantially higher for RAPD primers (0.35–4.65) than for SSR primers (0.35–1.73). It was possible to identify accessions, particularly those of divergent origins, by RAPD and (or) ISSR fingerprints. Based on these results, marker-based genetic improvement in A. hypogaea appears possible. None of the 486 RAPD and 330 ISSR amplification products were found to be commonly shared among 13 species of section Arachis and one species each of sections Heteranthae, Rhizomatosae, and Procumbentes. Dendrograms constructed from RAPD, ISSR, and RAPD + ISSR data showed overall similar topologies. They could be resolved into four groups corresponding to the species grouped in four taxonomic sections. The present results strongly support the view that Arachis monticola (2n = 4x = 40) and A. hypogaea are very closely related, and indicate that A. villosa and A. ipaensis are the diploid wild progenitors of these tetraploid species.Key words: Arachis hypogaea, genetic markers, varietal identification, DNA polymorphism, Arachis species. </jats:p