No abstract

Tomato bacterial wilt (BW) incited by Ralstonia solanacearum is a constraint on tomato production in tropical, subtropical and humid regions of the world. In this paper, we present the results of a research aimed at the identification of PCR-based markers amplified fragment length polymorphism (AFLP) linked to the genes that confer resistance to tomato BW. To this purpose, bulked segregant analysis was applied to an F(2) population segregating for the BW resistant gene and derived from the pair-cross between a BW resistant cultivar T51A and the susceptible cultivar T9230. Genetic analysis indicated that tomato BW was conferred by two incomplete dominant genes. A CTAB method for total DNA extraction, developed by Murray and Thompson with some modifications was used to isolation the infected tomato leaves. Thirteen differential fragments were detected using 256 primer combinations, and two AFLP markers were linked to the BW resistance. Subsequently, the AFLP markers were converted to co-dominant SCAR markers, named TSCAR(AAT/CGA) and TSCAR(AAG/CAT). Linkage analysis showed that the two markers are on the contralateral side of TRSR-1. Genetic distance between TSCAR(AAT/CGA) and TRS-1 was estimated to 4.6 cM, while 8.4 cM between TSCAR(AAG/CAT) and TRS-1.

Effect of plant growth regulators, explant size, season of explant collection, temperature (20, 25 and 30 °C) and photoperiod on in vitro lotus (Nelumbo nucifera Gaertn.) shoot formation and growth were examined. Shoots formation was greatly influenced by growth regulators, explant size and season of explant collection. The maximum number of shoots were induced from bud explants on Murashige and Skoog (MS) medium containing 4.44 μM benzyladenine (BA) + 0.54 μM α-naphthalene acetic acid (NAA). Explants formed by bud of one expanded and one unexpanded leaf, which was collected in spring gave encouraging results of shoot production. Higher temperature favoured shoot induction and subsequent growth was much better at 25 °C compared to that at 20 and 30 °C.

We combined cDNA amplified fragment length polymorphism (cDNA-AFLP) with bulked segregant analysis (BSA) to detect genes that control tomato (Lycopersicon esculentum) bacterial wilt infected with Ralstonia solanacearum, resistance in F 2 population derived from a cross between a bacterial wilt-resistant variety, T51A, and a bacterial wilt-susceptible variety, T9230. In cDNA-AFLP analysis among bulked-resistant F 2 (B R ) pool, bulked-susceptible F 2 (B S ) pool, bulked-resistant T51A (B A ) pool and bulked-susceptible T9230 (B B ) pool, 34 differentially expressed transcript-derived fragments (DE-TDFs) that were present in only B R and B A pools were detected. Analysis of differential DE-TDF expression in individual resistant F 2 resulted in the isolation of a caffeoyl CoA 3-Omethyltransferase (CCoAOMT) gene not previously described from tomato and which showed similarity to an CCoAOMT gene from tobacco and potato plants. This CCoAOMT gene may play a role in innate generalized response to pathogen infection as it was downregulated in susceptible tomato following infection with the bacterium. CCoAOMT gene plays an essential role in the synthesis of guaiacyl lignin units and supply substrates for the synthesis of syringyl lignin units.