scholarly journals GALUR HARAPAN TEMBAKAU TEMANGGUNG PRODUKSI TINGGI DAN TAHAN PENYAKIT LINCAT

2020 ◽  
Vol 13 (2) ◽  
pp. 57
Author(s):  
FATKHUR ROCHMAN ◽  
SUWARSO SUWARSO ◽  
A.S. MURDIYATI A.S. MURDIYATI
Keyword(s):  
Nicotiana Tabacum ◽  
Ralstonia Solanacearum ◽  
Phytophthora Nicotianae ◽  
Standard Variety ◽  
Root Knot Nematode ◽  
Nicotine Content ◽  
Meloidogyne Spp ◽  
Tobacco Cultivation ◽  
Grade Index ◽  
Moderately Resistant

ABSTRAK<br />Masalah  utama  tembakau  Temanggung  adalah  rendahnya<br />produktivitas yang disebabkan oleh mundurnya daya dukung lahan karena<br />erosi dan endemi penyakit lincat (kompleks nematoda Meloidogyne spp,<br />bakteri Ralstonia solanacearum, dan cendawan Phytophthora nicotianae).<br />Saat ini telah diperoleh enam galur hasil persilangan dari varietas Sindoro<br />1 (moderat tahan terhadap Ralstonia solanacearum tetapi rentan terhadap<br />Meloidogyne spp. dan sangat rentan terhadap Phytophthora nicotianae)<br />dengan tembakau virginia yang tahan terhadap ketiga patogen tersebut.<br />Evaluasi terhadap hasil, indeks mutu, indeks tanaman dan ketahanan<br />terhadap ketiga patogen telah dilakukan di 3 lokasi selama tiga tahun<br />dengan rancangan acak kelompok tiga ulangan. Hasil penelitian<br />menunjukkan bahwa ada dua galur harapan yaitu (1) Galur A dengan rata-<br />rata produktivitas : 0,880 ton rajangan kering per ha dan indeks mutu<br />40,28 indeks tanaman 35,47 dan kadar nikotin 5,52%. Produktivitas galur<br />A meningkat 48,08%, indeks mutu meningkat 4,87% dan indeks tanaman<br />meningkat 53,73% serta kadar nikotin menurun 15,06% dibanding varietas<br />standar. Galur A memiliki sifat moderat tahan terhadap bakteri Ralstonia<br />solanacearum dan toleran terhadap nematoda Meloidogyne spp. (2) Galur<br />E dengan rata-rata produktivitas : 0,869 ton rajangan kering per ha, indeks<br />mutu 36,01 indeks tanaman 31,87 dan kadar nikotin 6,00%. Produktivitas<br />galur E meningkat 46,23%, indeks mutu menurun 6,25% dan indeks<br />tanaman meningkat 38,12% serta kadar nikotin menurun 2,56% dibanding<br />varietas standar. Galur E memiliki sifat moderat tahan terhadap bakteri<br />Ralstonia solanacearum dan toleran terhadap nematoda Meloidogyne spp.<br />Kata kunci : Tembakau,  Nicotiana  tabacum,  Temanggung, galur<br />harapan, Ralstonia solanacearum, Meloidogyne spp,<br />Phytophthora nicotianae, lahan lincat, Jawa Timur<br />ABSTRACT<br />Temanggung tobacco promising lines with high producti-<br />vity and resistant to lincat diseased<br />The main problem in Temanggung tobacco cultivation is low<br />productivity which is caused by increasing land erosion and invasion of<br />endemic disease called ‘lincat’. Lincat is a disease caused by a complex<br />invasion of three pathogens i.e. Meloidogyne spp. (root-knot nematode),<br />Ralstonia solanacearum (bacteria) and Phytophthora nicotianae (fungus).<br />Hybridization between variety Sindoro 1 (moderately resistant to R.<br />solanacearum but susceptible to Meloidogyne spp. and highly susceptible<br />to P. nicotianae) and virginia tobacco (resistant to these three pathogens)<br />has resulted in six lines. These lines were planted in three locations for 3<br />years and were evaluated for their yield, grade index, crop index, and<br />resistance intensity to these three pathogens, using randomized block<br />design with 3 replications. Two promising lines were resulted from this<br />evaluation i.e. (1) Line A, that has productivity of tobacco sliced : 0.880<br />ton per hectare, grade index: 40.28 crop index: 35.47 and nicotine content:<br />5.52%. In comparison to standard variety, the productivity, grade index,<br />and crop index of this line increased of 48.08%, 4.87%, and 53.73%,<br />respectively, and nicotine content decreased of 15.06%. Moreover, this<br />line is moderately resistant to R. solanacearum and tolerant to<br />Meloidogyne spp. (2) Line E, that has productivity of tobacco sliced:<br />0.869 ton per hectare, grade index: 36.01 crop index: 31.87 and nicotine<br />content: 6.00%. This line also has increase productivity, and crop index of<br />46.23% 38.12%, respectively, and has decrease grade index and nicotine<br />content of 6.25% and 2.56%, respectively compared to standard variety.<br />This line is moderately resistant to R. solanacearum and tolerant to<br />Meloidogyne spp.<br />Key words : Tobacco, Nicotiana tabacum, Temanggung, promising line,<br />Ralstonia solanacearum, Meloidogyne spp., Phytophthora<br />nicotianae, lincat land, East Jav

scholarly journals KARAKTER PERTUMBUHAN, KETAHANAN TERHADAP PENYAKIT, DAN KADAR NIKOTIN BEBERAPA GALUR TEMBAKAU TEMANGGUNG

2020 ◽  
Vol 18 (3) ◽  
pp. 102
Author(s):  
FATKHUR ROCHMAN
Keyword(s):  
Nicotiana Tabacum ◽  
Ralstonia Solanacearum ◽  
Consumer Preferences ◽  
Leaf Size ◽  
Phytophthora Nicotianae ◽  
Dry Land ◽  
Nicotine Content ◽  
Meloidogyne Spp ◽  
Tobacco Cultivation ◽  
Consumer Tastes

<p>ABSTRAK<br />Pergeseran selera konsumen ke arah rokok ringan semakin nyata,<br />sehingga dirasa perlu memiliki galur-galur tembakau temanggung dengan<br />kadar nikotin rendah dan mutu sesuai dengan selera konsumen. Tembakau<br />temanggung memiliki kadar nikotin yang sangat tinggi (7,8%). Selain<br />kadar nikotin, kendala utama budi daya tembakau temanggung adalah<br />adanya penyakit tular tanah yang disebabkan oleh kompleks nematoda<br />Meloidogyne spp,  bakteri Ralstonia  solanacearum, dan  jamur<br />Phytophthora nicotianae yang dikenal dengan nama ‘penyakit lincat”.<br />Penelitian ini bertujuan untuk memperoleh galur tembakau temanggung<br />dengan kadar nikotin lebih rendah dari varietas yang sudah ada (Kemloko<br />1 dan Kemloko 2), mutu sesuai untuk konsumen, dan toleran terhadap<br />penyakit utama. Penelitian dilaksanakan mulai bulan Februari sampai<br />Oktober 2009, di Desa Gandurejo, Kecamatan Bulu, Kabupaten<br />Temanggung pada lahan tegal endemik tiga patogen dengan ketinggian<br />tempat + 800 m dpl. Bahan penelitian terdiri atas tujuh genotipe F6 hasil<br />persilangan antara tembakau temanggung dan tembakau oriental. Masing-<br />masing genotipe ditanam sebanyak 520 tanaman. Seleksi pertama<br />dilakukan berdasarkan kriteria: tidak terserang penyakit, memiliki lebih<br />dari 18 daun, ukuran daun sedang sampai besar, morfologi mirip daun<br />tembakau  temanggung, dan  disenangi  petani. Hasil  penelitian<br />menunjukkan bahwa dari 2.436 tanaman yang tidak diserang penyakit<br />(berasal dari tujuh genotipe) secara visual terpilih 302 tanaman.<br />Berdasarkan ukuran daun, dari 302 tanaman terpilih tersebut diperoleh 40<br />genotipe. Keempat puluh genotipe tersebut dievaluasi pada tahap<br />berikutnya. Kadar nikotin semua galur berkisar 1,34-5,22% dan galur yang<br />memiliki rata-rata kadar nikotin terendah adalah genotipe hasil persilangan<br />antara Kemloko 1 dan Xanthi Yacca.<br />Kata kunci: persilangan, Nicotiana tabacum, kadar nikotin, tembakau<br />oriental, tembakau temanggung</p><p>ABSTRACT<br />A shift in consumer tastes toward lighter cigarette has led to finding<br />of low nicotine content of temanggung tobacco with the quality suitable to<br />consumer preferences. The nicotine content of temanggung tobacco is very<br />high, which can reach 7.8%. One of the main problem of temanggung<br />tobacco cultivation is soil born diseases caused by complexity of<br />nematodes Meloidogyne spp, Ralstonia solanacearum, and the fungi<br />Phytophthora nicotianae which is known as “lincat”. The research aimed<br />at obtaining hybrid lines of temanggung tobacco with nicotine levels lower<br />than the existing varieties (Kemloko 1 and Kemloko 2), quality suitable to<br />consumers preferences, and tolerant to the main diseases. The experiment<br />was conducted from February to Oktober 2009 in Gandurejo Village Bulu<br />Subdistrict, Temanggung District, on the dry land endemic pathogens with<br />altitude about 800 m asl. Research material consisted of 7 genotypes F6<br />from hybridization between temanggung and orient tobacco, and 5 parental<br />varieties. As many as 520 crops of each genotype were planted. First<br />selection was done based on the criteria: free from disease, having &gt; 18<br />leaves, medium to big leaf size, and farmers’ favorite. The results showed<br />that from 2,436 healthy plants (derived from 7 genotypes) were visually<br />selected for 302 plants. From the second selection based on leaf size from<br />the 302 plants obtained 40 genotypes. The forty genotypes were<br />evaluated/screened at later stage. Nicotine content ranged from 1.07 to<br />5.22% and the lowest nicotine content was derived from crosses between<br />Kemloko 1 and Xanthi Yacca.<br />Key words: hybrid progenies, Nicotiana tabacum, nicotine content,<br />orient tobacco, temanggung tobacco</p>

Resistance in Mungbean Against Meloidogyne incognita and its Impact on Nodulation

2020 ◽  
Author(s):  
Narpinderjeet Kaur Dhillon ◽  
Rohit Kumar ◽  
Sukhjeet Kaur ◽  
Anupam Anupam ◽  
Asmita Srari
Keyword(s):  
Plant Growth ◽  
Growth Parameters ◽  
Root Knot Nematode ◽  
Sources Of Resistance ◽  
Kharif Season ◽  
Breeding Programmes ◽  
Meloidogyne Spp ◽  
Moderately Resistant ◽  
The Impact ◽  
Resistant Genotypes

Mungbean is an economically as well as nutritionally enriched crop. Of the different soil borne pathogens attacking mungbean, root-knot nematode (Meloidogyne spp.) is an important pathogen affecting growth and production of mungbean. It is grown in summer as well as in kharif season. The germplasm of mungbean of two seasons’ viz., summer and kharif was screened to identify new sources of resistance against root knot nematode, M. incognita. In addition to screening; studies were also conducted on the impact of root knot nematode infestation in roots on nodulation character of mungbean and growth parameters. Of the sixty three genotypes evaluated in summer, seven were found to be moderately resistant. In kharif season, only three genotypes were found to be moderately resistant. M. incognita infestation was also observed to affect the plant growth parameters as well as nodulation on roots of mungbean genotypes. Comparatively, better plant growth and higher nodulation was observed in moderately resistant genotypes as compared to the susceptible ones. The ten identified moderately resistant genotypes from two seasons can be a useful source in breeding programmes for developing cultivars to manage root knot nematode.

scholarly journals PENGENDALIAN TERPADU PENYAKIT LAYU (RALSTONIA SOLANACEARUM Smith) DAN NEMATODA PURU AKAR (MELOIDOGYNE SPP.) PADA TANAMAN JAHE GAJAH

2005 ◽  
Vol 5 (2) ◽  
pp. 97-103
Author(s):  
Made Sudana ◽  
Made Lotrini
Keyword(s):  
Ralstonia Solanacearum ◽  
Seed Treatment ◽  
Plant Root ◽  
Integrated Control ◽  
Block Design ◽  
Research Result ◽  
Wilt Disease ◽  
Root Knot Nematode ◽  
Plant Seed ◽  
Meloidogyne Spp

Integrated control of  ginger wilt disease  (Ralstonia solanacearum Smith) and root knot nematodes (Meloidogyne spp.). The purpose of this research was to obtain  reasonable integrated control ginger wilt disease. The research was conducted in endemic area of ginger wilt disease at Biaung village, Penebel Regency during April, 2003 to Januari, 2004. Randomized block design (RAK) with three replication and 11 treatments was used in this experiment. Research result appears that ginger wilt diseases can be controlled by integrated control using seed treatment with soaked method in urea-polymer + Bacillus sp. (2g/l water for two hours and then for planting treatment with vermi-compost (150g/plant) + fire-wood ash (50g/plant) + Mycorrhiza (100 g/plant). Root knot nematode (Meloidogyne spp.) was effective controlled by dolomit (5g/plant) + seed-treatment with bactericide (Agrimicin 500 ppm) +  vermi-compost (150 g/plant).

scholarly journals ANALISIS LINTAS SIFAT-SIFAT AGRONOMIS TERHADAP INDEKS TANAMAN DAN KADAR NIKOTIN TEMBAKAU VIRGINIA BOJONEGORO

2020 ◽  
Vol 10 (3) ◽  
pp. 83
Author(s):  
. ADJISASTROSUPADI ◽  
A. S. MURDIYATI
Keyword(s):  
Nicotiana Tabacum ◽  
Path Analysis ◽  
Leaf Area ◽  
Leaf Number ◽  
Path Coefficient ◽  
Nicotine Content ◽  
Independent Variables ◽  
Main Independent Variable ◽  
Grade Index ◽  
The Relationship

<p>Hubungan sifat-sifat agronomis terhadap indeks tanaman dan kadar nikotin telah dicari dengan analisis lintas. Tujuan dari analisis adalah untuk mengetahui pcubah bebas yang sangat mempengaruhi peubah yang tidak bebas, indeks mutu dan kadar nikotin daun, sehingga dapat mengurangi banyaknya pengamatan yang dilakukan. Data pengamatan agronomis yang meliputi : jumlah daun/pohon, luas daun ke-7, luas daun ke-15, bobot rajangan kering/ha, indeks mutu dan indeks tanaman diperoleh dari percobaan pemupukan tiga galur harapan tembakau Virginia di kebun percobaan Pekuwon Bojonegoro dari bulan Mei sampai dengan Oktober 2002. Hasil analisis lintas antara indeks tanaman dengan peubah bebas di atas menunjukkan bahwa indeks tanaman sangat ditentukan oleh bobot rajangan kering dengan koefisien lintas pm-1.03367 dan koefisien dcterminasi parsial 102%. Hubungan lintas bcrantai melalui pcubah rajangan kering dan indeks mutu menunjukkan bahwa luas daun kc-7 sangat mempengaruhi rajangan kering dengan koefisien lintas (p„i)- 0.85257 dan rajangan kering sangat mempengaruhi indeks tanaman dengan koefisien lintas (p,x,)= 0.95639, indeks mutu pengaruhnya terhadap indeks lanaman sangat kecil dengan koefisien lintas p,M = 0.12316. Analisis lintas antara kadar nikotin daun dengan ke lima peubah tidak baik (unfit) dengan koefisien sisa p„,= 0.6827 melebihi koefisien lintas yang lainnya. Dengan pentingnya peubah rajangan kering ini maka penjualan daun segar yang dilakukan oleh petani tidak dianjurkan.<br /><br />Kata kunci: Nicotiana tabacum, tembakau Virginia, analisis lintas, jumlah daun, luas daun, indeks tanaman, indeks mutu, kadar nikotin, bobot rajangan ABSTRACT Path analysis of agronomical characteristics on crops index and nicotine content of Virginia tobacco Bojonegoro The relationship between agronomical characteristics and crops index or leaf nicotine content has been studied by using path analysis. The purpose of this analysis was to determine the independent variables which most affected the dependent ones as crops index and leaf nicotine contain, so that it could reduce the number of independent variables. The agronomical characteristics consist of leaf number/plant, seventh and fiteenth leaf area, dried slice leaf/ha, grade index and crop index obtained from fetilizer experiment on three Virginia tobacco lines at Pekuwon Experimental Garden Bojonegoro, from May to October 2002. The results of this path analysis showed that crop index was strongly affected by dried slice leaf with path coeficient poi = 1.03367 and patial determination coefficient 102%. It was indicated that dried slice leaf was strongly affected by seventh leaf area with path coefficient p,n- 0.85257 and dried slice leaf strongly variable affected the crop index with path coeficient poi= 0.95639, while the grade index had little effect on crop index with path coefficient poi= 0.12316. The path analysis between leaf nicotine content and ive variables above was unfit with residual path coeficient pou= 0.6827, it was higher than each path coefficient of the orther variables. The dried slice leaf was the main independent variable affecting the crops index, so that selling of fresh tobacco leaves by farmers is not recomended.</p><p>Key words : Nicotiana tabacum, Virginia tobacco, path analysis, leaf number, leaf area, crop index, grade index, nicotine content, dried slice leaf</p>

scholarly journals Aktivitas Antagonis Bakteri Endofit Asal Mangrove terhadap Ralstonia solanacearum dan Meloidogyne spp.

2018 ◽  
Vol 14 (1) ◽  
pp. 23
Author(s):  
Muhammad Firdaus Oktafiyanto ◽  
Abdul Munif ◽  
Kikin Hamzah Mutaqin
Keyword(s):  
Ralstonia Solanacearum ◽  
Endophytic Bacteria ◽  
Plant Pathogens ◽  
Control Plant ◽  
In Vitro Test ◽  
Root Knot Nematode ◽  
New Information ◽  
Meloidogyne Spp ◽  
Vitro Test

The main diseases of tomato caused by wilt bacteria (Ralstonia solanacearum) and root knot nematodes (Meloidogyne spp.) may cause significant yield losses and need to be managed. Recently, biocontrol approach especially using endophytic bacteria has been developed to control plant pathogens. This research was aimed to obtain endophytic bacteria from 2 species of mangrove, which effectively controlled root knot nematode and wilt bacteria. A total of 843 endophytic bacteria were successfully isolated from 2 species of mangroves. The bacteria isolates were further subjected for biosafety assay. The results of the test showed that 403 endophytic bacteria gave negative reaction in hypersensitive and hemolytic tests. Furthermore, 19 isolates effectively suppressed the growth R solanacearum and killed Meloidogyne in in vitro test. Physiological test showed that 14 and 11 isolates of the bacteria were able to produce protease and chitinase, respectively. This research provides a new information that endophytic bacteria from mangrove has a potency as a biocontrol agents.

scholarly journals Variations in the level of resistance to root-knot nematodes (Meloidogyne spp.) infestation among ten cowpeas (Vigna unguiculata L. Walp.) genotypes

2019 ◽  
Vol 54 (2) ◽  
pp. 68-78
Author(s):  
F. Kankam ◽  
E. N.K. Sowley ◽  
J. Adomako ◽  
A. Boateng
Keyword(s):  
Vigna Unguiculata ◽  
Root Knot Nematode ◽  
Root Knot Nematodes ◽  
Second Stage ◽  
Randomized Design ◽  
Significant Difference ◽  
Environmentally Safe ◽  
Meloidogyne Spp ◽  
The University ◽  
Moderately Resistant

The cultivation of cowpea (Vigna unguiculata L. Walp.) cultivars that are tolerant to root-knot nematode attack is among the environmentally safe approach to managing the root-knot nematode menace in cultivated crops. In this study, the tolerance of 10 cowpea genotypes to root-knot nematodes infestation was evaluated in a pot experiment conducted in a Screenhouse, at the University for Development Studies, Nyankpala Campus. The experiment was laid out in a completely randomized design with three replications. The number of second stage juveniles (J2) per 250 cm3 of soil sample were counted while the severity of root-knot nematode damage (root galls) was assessed. The reproduction index (RI) was used to classify the varieties as resistant or susceptible. There was a significant difference (P < 0.05) in the number of second stage juveniles of root-knot nematode (RKN), galling index and RI among the genotypes tested. The study revealed that cowpea genotypes SARI 1-4-90, Padi tuya, Songotra, IT99K-1122, Sanzi and Apagbaala were moderately resistant whereas cowpea genotypes IT86D-610, Zaayura, SARI 5-5-5 and IT07K-299-6 were slightly resistant. Thus, the six moderately resistant cowpea genotypes were suggested to be used as a source of resistance to RKN in future breeding works.

scholarly journals Root-knot Nematode Resistance in Cucumber and Horned Cucumber

HortScience ◽  
1993 ◽  
Vol 28 (2) ◽  
pp. 151-154 ◽  
Author(s):  
S. Alan Walters ◽  
Todd C. Wehner ◽  
Kenneth R. Barkel
Keyword(s):  
Cucumis Sativus ◽  
Nematode Resistance ◽  
Plant Introduction ◽  
Root Knot Nematode ◽  
Root Knot Nematodes ◽  
Breeding Lines ◽  
Meloidogyne Spp ◽  
Race 2 ◽  
Moderately Resistant

Cucumber (Cucumis sativus L.) and horned cucumber (C. metuliferus Naud.) germplasm were evaluated for their resistance to root-knot nematodes (Meloidogyne spp.). All 24 C. metuliferus cultigens evaluated were resistant to all root-knot nematodes tested-M. incognita (Kofoid and White) Chitwood race 3, M. arenaria (Neal) Chitwood race 2, and M. hapla Chitwood. All 884 C. sativus cultigens (cultivars, breeding lines, and plant introduction accessions) tested were resistant to M. hapla and few to M. incognita race 3. Only 50 of 884 C. sativus cultigens evaluated were somewhat resistant to M. arenaria race 2 and M. incognita race 3. A retest of the most resistant C. sativus cultigens revealed that LJ 90430 [an accession of C. sativus var. hardwickii (R.) Alef.] and `Mincu' were the only cultigens that were moderately resistant to M. arenaria race 2. LJ 90430 was the only cultigen, besides the two retested C. metuliferus cultigens, that was resistant to M. javanica (Treub) Chitwood. All C. sativus cultigens retested, including LJ 90430, were highly susceptible to M. incognita races 1 and 3. The two C. metuliferus cultigens retested were highly resistant to all root-knot nematodes tested-M. arenaria race 2, M. incognita races 1 and 3, and M. javanica.

Sources of resistance to Fusarium wilt and root-knot nematode in indigenous chickpea germplasm

2012 ◽  
Vol 10 (3) ◽  
pp. 258-260 ◽  
Author(s):  
Mohar Singh ◽  
Z. Khan ◽  
Krishna Kumar ◽  
M. Dutta ◽  
Anju Pathania ◽  
...  
Keyword(s):  
Fusarium Wilt ◽  
Rating Scale ◽  
Resistance Breeding ◽  
Practical Method ◽  
Root Knot Nematode ◽  
Sources Of Resistance ◽  
Chickpea Wilt ◽  
Breeding Programmes ◽  
Race 1 ◽  
Moderately Resistant

Fusarium wilt caused by Fusarium oxysporum, Schlecht. emend. Snyd. & Hans. f. sp. ciceri is prevalent in most chickpea-growing countries and is a major devastating disease. Host plant resistance is the most practical method of disease management. Indigenous chickpea germplasm reveals a heterogeneous genetic make-up and the response of resistance to wilt is an unexplored potential source for disease resistance. There are 70 indigenous germplasm lines selected on the basis of their agronomic performance and diverse areas of collections in the country. Of these, four accessions had a highly resistant score of 1 and six had a score of 3 using a 1–9 rating scale, indicating their level of resistance to Fusarium wilt (race 4). Other germplasm accessions of chickpea were found to be moderately resistant to highly susceptible disease reaction. Likewise, the same set of germplasm was also screened for Meloidogyne incognita (race 1) using pot culture under controlled condition. Only one accession was found to be resistant to this pest. These resistant gene sources can be utilised effectively for race-specific chickpea wilt and root-knot resistance breeding programmes.

Genetic diversity of Meloidogyne spp. parasitising potato in Brazil and aggressiveness of M. javanica populations on susceptible cultivars

Nematology ◽  
2017 ◽  
Vol 19 (1) ◽  
pp. 69-80 ◽  
Author(s):  
Israel L. Medina ◽  
Cesar B. Gomes ◽  
Valdir R. Correa ◽  
Vanessa S. Mattos ◽  
Philippe Castagnone-Sereno ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Rapd Markers ◽  
Potato Production ◽  
Potato Cultivars ◽  
Root Knot Nematode ◽  
Root Knot Nematodes ◽  
Nematode Reproduction ◽  
Meloidogyne Spp ◽  
Prevalent Species ◽  
Reproduction Factor

Root-knot nematodes (Meloidogyne spp.) significantly impact potato production worldwide and in Brazil they are considered one of the most important group of nematodes affecting potatoes. The objectives of this study were to survey Meloidogyne spp. associated with potatoes in Brazil, determine their genetic diversity and assess the aggressiveness of M. javanica on two susceptible potato cultivars. Fifty-seven root-knot nematode populations were identified using esterase phenotyping, including Meloidogyne javanica, M. incognita, M. arenaria and M. ethiopica. Overall, root-knot nematodes were present in ca 43% of sampled sites, in which M. javanica was the most prevalent species, and the phenotypes Est J3, J2a and J2 occurred in 91.2, 6.7 and 2.1% of the positive samples, respectively. Other species, such as M. incognita, M. arenaria and M. ethiopica, were found less frequently and occurred at rates of 6.4, 4.3 and 2.1% of the samples, respectively. Sometimes, M. javanica was found in mixtures with other root-knot nematodes in ca 10.6% of sites containing Meloidogyne. After confirming the identification of 17 isolates of M. javanica and one isolate each of M. incognita, M. arenaria and M. ethiopica by SCAR markers, the populations were used to infer their genetic diversity using RAPD markers. Results revealed low intraspecifc genetic diversity among isolates (13.9%) for M. javanica. Similarly, M. javanica sub-populations (J2a) clustered together (81% of bootstrap), indicating subtle variation from typical J3 populations. The aggressiveness of four populations of M. javanica from different Brazilian states on two susceptible potato cultivars was tested under glasshouse conditions. Results indicated differences in aggressiveness among these populations and showed that potato disease was proportional to nematode reproduction factor.

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