Reaction of Cotton Cultivars and an F₂ Population to Stem Inoculation with Isolates Verticillium dahliae

Abstract

Four Verticillium dahliae isolates (V76, TS-2, PH, and V44) were used in screening four cotton cultivars (Pima S-7, Acala Prema, M-315 and Acala 44). Pima S-7 and Acala Prema gave the highest resistance reactions and Acala 44 was the most susceptible. Isolate V76 of V. dahliae was the most virulent. An interspecific cross between the resistant cv Pima S-7 (Gossypium barbadense) and the susceptible cv. Acala 44 (G. hirsutum) was made and the F 2 population phenotyped for Verticillium wilt effect. Phenotyping of plant reaction to the disease was quantified by using a set of six growth parameters (number of healthy leaves, number of nodes, leaf weight, stem weight, leaf to stem ratio, and total shoot weight) measured 3 weeks after inoculation. The F 2 phenotypic distribution of these parameters suggests that distribution is towards resistance and polygenic. Transgressive segregation also was observed. The number of healthy leaves and total shoot weight were found to be the best indicators of resistance. Results obtained in this study will be useful to quantify resistance to V. dahliae and identify the best parameters to phenotype in genetic studies.

Mapping Fusarium wilt race 1 resistance genes in cotton by inheritance, QTL and sequencing composition

“…Genetic and physical framework mapping in cotton are used to discover putative gene sequences involved in resistance to FOV, nematodes and possibly other common soil pathogens. For example, chromosome 11 houses resistance to race 1 FOV and root-knot nematode , reniform nematode (Dighe et al 2009) and Verticillium wilt (Bolek et al 2005). Additional genome sequencing coupled with physical alignment of genomic regions into chromosomal maps will expedite discovery of R or PR genes underlying QTLs and will offer candidate gene sets for functional analyses of plant defense against Fusarium wilt and other biotrophic pathogens.…”

A transgressive segregation factor (RKN2) in Gossypium barbadense for nematode resistance clusters with gene rkn1 in G. hirsutum

“…Transgressive segregation has been observed not only in cotton-pathogen resistance (Bolek et al 2005;Bayles et al 2005; this study) and other plant-pathogen resistance systems (Cherif and Harrabi 1993;Zhang et al 2001;Imtiaz et al 2003a, b;Navabi et al 2004;Zhao et al 2005;Staal et al 2006;Winter et al 2007), but also for other traits, such as Wber quality (Percy and Turcotte 1988;Kohel et al 2001;Jenkins et al 2007) and yield in cotton, agronomic traits in tomato (de Vicente and Tanksley 1993), and protein content in rice (Hu et al 2004;Watanabe et al 2006). Thus, transgressive segregation for pathogen resistance and other traits is quite common in plants.…”

“…Transgressive segregation is one of the major selection sources in cotton for enhanced resistance to root-knot nematode (Meloidogyne incognita Kofoid and White (Chitwood)), an important pest of cotton (Goodell and Montez 1994). Transgressive segregation also has been observed in other pathogen-cotton systems, such as for Verticillium wilt resistance in an F 2 (resistant G. barbadense Pima S-7 £ susceptible Acala 44) (Bolek et al 2005), and for Fusarium wilt resistance in the F 2 or F 3 (resistant Pima S-7 £ susceptible Acala SJ-2 or susceptible Acala NemX) . A susceptible parent was found to contribute to bacterial blight resistance in the BC 4 F 4 generation within an intraspeciWc cross of cotton (Bayles et al 2005).…”

Response of AtNPR1-expressing cotton plants to Fusarium oxysporum f. sp. vasinfectum isolates

“…Conidial count was obtained using a haemocytometer and the final count was adjusted to 10 7 conidia/ml by diluting with sterile distilled water. A 23-gauge needle was used to inoculate 4-week-old cotton plants using the stem puncture method (Bugbee and Presley 1967;Bolek et al 2005). Distilled water was used in place of the inoculum for mock treatment.…”