The southern root-knot nematode (SRKN; Meloidogyne incognita) is one of the main pathogens for tobacco. The objectives of this study were to determine the genetic parameters and heritability of SRKN resistance in air-cured tobacco. For this purpose three resistant parents (Urmia3, KY9, K17) and two susceptible parents (Ergo, Burley TMV4) were crossed based on half diallel and analyzed by Hayman's method for reaction to Meloidogyne incognita. Fifteen genotypes (parents and hybrids) were planted in the greenhouse in a completely randomized design with five replications and inoculated with 2500 J2 M. incognita race 2 one week after transplanting. Investigation of gall index (GI), number of egg masses (NEM) and average number of eggs per mass (AEM) showed significant differences among genotypes. Non-additive effects in AEM and additive effects in GI and NEM played an important role. Narrow-sense heritability was estimated as 0.75, 0.56 and 0.28 for GI, NEM and AEM, respectively, which revealed that AEM is not a suitable trait for nematode resistance identification. Regression analysis indicated that KY9 is an appropriate donor parent for SRKN resistance. Resistance to M. incognita race 2 is conditioned by a single partially dominant gene.

This study was performed to genetical and morphological investigation of a novel chlorophyll deficiency gene in tobacco leaf. One low chlorophyll content (LCC) variety (Urumieh 2) and high chlorophyll content (HCC) variety (Burley Ree 103) from the Burley type was crossed and the F2 generation was grown on the field. One hundred plants were selected, contained low and high chlorophyll content. These plants were sampled and DNA was extracted. Sixty RAPD primers were tested on parents, LCC and HCC Bulks based on Bulk Segregant Analysis (BSA). Chi-square test confirmed the monogenic segregation. Regresion analysis showed that there was strong relationship between greenness degree and chlorophyll contents. Four primers (OPE17, OPC09, OPB08 and OPR02) showed polymorphism and after the test on 97 samples from the F2 generation two markers were selected (OPB08-1050 and OPC09-1900). That showed 15.9 and 10.8 CM distance from chlorophyll locus respectively.

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Shahadati-Moghaddam Z. and N. Bagheri (2019): Expression analysis of proteinase inhibitor type-2 in response to Vol 51, No.3,[923][924][925][926][927][928][929][930][931][932][933][934][935][936] are polypeptides that occur naturally in a wide range of plants and are considered to be an essential part of the plant's natural defense system. The aims of this study were to determine effect of PI2-N. tabacum in nematode (Meloidogyne incognita) resistance and its characterize. Resistant (KY9) and susceptible (Ergo) genotypes were inoculated by M. incognita race 2 and total RNA were extracted from roots. Exclusive primers were used for PI2 (Q40561) and EF1α (reference gene) in qPCR to determine PI2 level changes in two, three and four days after inoculation. Results showed significant difference of PI2 expression in resistant and susceptible genotypes in two-four days after inoculation. Bioinformatics analysis revealed PI2 is an unstable protein and has three proteinase inhibitory domains with a trance membrane region. Proteinase inhibitory domains are trypsin and chymotrypsin inhibitor. Alignment and phylogenetic relationship of inhibitor precursor-repeats in Nicotiana sp. revealed seven groups that were variable in sequence. However, they had conserved residues including eight cysteines, a single proline and three Glycine.