Resistance to Xanthomonas spp. in Tomato: Diallel Analysis and Gene Effects Estimative in a Breeding Programme Carried out in Brazil

Abstract

Tomato bacterial spot, caused by Xanthomonas campestris pv. vesicatoria [Applied Environment Microbiology 71 (2005) 3581], occurs worldwide, wherever tomato is cultivated. The control in the field is hampered by the low efficiency of protective chemicals due to predominantly resistant strains to streptomycin sulphate and copper-based products [Journal of Phytopathology 147 (1999) 397]. Genetic resistance is a more promising alternative for the establishment of cultivations that are more profitable and, above all, less harmful to the ecosystem. In this study, six tomato genotypes and their hybrid diallel combinations, without the reciprocals, were investigated for their reaction to bacterial spot caused by three Xanthomonas races [Annual Review of Phytopathology 36 (1998) 41]. Resistance was rated on a grade scale, and by the area under disease progress curve. The diallel analysis was performed according to Griffing [Australian Journal of Biological Sciences 9 (1956) 463], Method 2, Model B. The accession UENF 157 was found to be resistant to all pathogen races and UENF 158 to T2. Resistance to T1 was observed in hybrid UENF 155 · UENF 157 and moderate resistance to T2 in UENF 155 · ÕSanta AdeliaÕ, UENF 155 · UENF 222 and UENF 157 · UENF 222. In the reaction to T1, additive gene effects were predominant and dominance effects in the resistance to T3. Recessive genes contributed to reduce the manifestation of lesions of the three races as indicated by the two resistance components evaluated.

First report of bacterial spot caused by Xanthomonas campestris pv. vesicatoria race 2 on tomato in Nepal

“…Hawai 7998, Hawai 7981 and John Baer. The first two are resistant respectively to races 1 and 3 and all of them are susceptible to race 2 of the pathogen (De Souza et al, 2008).The bacterial isolate caused symptoms on all three cultivars, confirming that it belongs to race 2. Bacteria re-isolated from the necrotic lesions were shown to be identical to the original strains according to the morphological, cultural and biochemical tests described above.…”

“…Hawai 7998, Hawai 7981 and John Baer. The first two are resistant respectively to races 1 and 3 and all of them are susceptible to race 2 of the pathogen (De Souza et al , 2008). The bacterial isolate caused symptoms on all three cultivars, confirming that it belongs to race 2.…”

Critical disease components of common bacterial blight to effectively evaluate resistant genotypes of snap bean

“…For this process, each isolate (1394-98 and 775-90) was scratched onto a plaque containing solid DYGS medium (g/L: 2.0 g/L dextrose, 1.5 g/L bacteriological peptone, 2.0 g/L yeast extract, 0.5 g/L K 2 HPO 4 , 0.5 g/L MgSO 4 Á7H 2 O, 1.5 g/L glutamic acid, 18.0 g/L agar, pH 7.0, according to Rodrigues Neto et al 1986 andde Souza et al 2008) with a platinum loop. After 36 h, the bacterial colonies were suspended in distilled water, and the cell concentration was adjusted to 10 8 CFU/mL using a spectrophotometer at an absorbance of 640 nm and diluted to 10 7 CFU/mL.…”

<b>Combining ability for common bacterial blight resistance in snap and dry bean (<i>Phaseolus vulgaris</i> L.)

“…Xap inoculation in the leaves was performed 25 days after planting. The isolates were cultivated separately in Petri dishes that contained solid DYGS medium (in g L -1 : dextrose, 2.0; bacteriological peptone, 1.5; yeast extract, 2.0; K 2 HPO 4 , 0.5; MgSO 4 .7H 2 O, 0.5; glutamic acid, 1.5 and agar, 18.0, pH 7.0) according to Rodrigues Neto et al (1986) and Souza et al (2008). After 36 hours, the bacterial colonies were suspended in distilled water, and the cell concentration was adjusted to 10 8 colony forming units per millilitre (cfu.…”