Inheritance of southern root-knot nematode resistance in air-cured tobacco

Abstract

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.

The impact of linkage disequilibrium and epistasis in the studies of inheritance based on Hayman’s diallel and generation mean analysis

“…Unfortunately, this was not observed in some recently published studies (Pessoa et al 2019;de Lima et al 2019;Shahadati-Moghaddam et al 2017). Thus, breeders must realize that LD and epistasis are not their major problem when processing a Hayman's diallel analysis, but the experimental error.…”

“…In the context of inheritance, an interesting approach based on diallel cross was proposed by Hayman (1954). However, very few inheritance studies based on Hayman's method were published in the last 10 years (de Lima et al 2019;Makumbi et al 2018;Shahadati-Moghaddam et al 2017;Kalinina and Lyakh 2011). The Hayman's method has indeed some limitations, as the assumptions of no epistasis (independent action of non-allelic genes) and no linkage disequilibrium (LD) (genes independently distributed in the parents).…”

Expression analysis of proteinase inhibitor type-2 in response to southern root-knot nematode and its characterization in Nicotiana tabacum

“…One SRKN resistant tobacco genotype (Nicotiana tabacum; KY9) and a susceptible genotype (Ergo) were planted in Plastic pots (1.5 L) with sterilized sandy loam soil and maintained in the greenhouse at the Tirtash Research & Education Center, Behshahr, Iran (SHAHADATI-MOGHADDAM et al, 2017).…”

The impact of linkage disequilibrium and epistasis in the studies of inheritance based on Hayman’s diallel and generation mean analysis

“…In the context of inheritance, an interesting approach based on diallel cross was proposed by Hayman (1954). However, very few inheritance studies based on Hayman's method were published in the last 10 years (de Lima et al 2019;Makumbi et al 2018;Shahadati-Moghaddam et al 2017;Kalinina and Lyakh 2011). The Hayman's method has indeed some limitations, as the assumptions of no epistasis (independent action of non-allelic genes) and no linkage disequilibrium (LD) (genes independently distributed in the parents).…”