Abstract

GARCIA-LARA, Erika et al. Infection process to wheat leaf rust (Puccinia triticina Erikson) in genotipes with partial resistance. Agrociencia [online]. 2007, vol.41, n.7, pp.775-785. ISSN 2521-9766.

With the purpose to understand partial resistance mechanisms, which the genes Lr34, Lr46, and one gene (Gene 1) not yet named confer to prehaustorial resistance, presented by some wheat genotypes with partial resistance to leaf rust caused by Puccinia triticina, the infection process in wheat genotypes containing genes with partial resistance was studied: Jupateco 73R+Lr34, Avocet+Lr34, Lalbahadur+Lr46, and Lalbahadur+Gene 1, and in genotypes that do not contain the gene: Jupateco 73S-Lr34, Avocet-Lr34, and Lalbahadur. The objective was to recognize the resistance mechanisms which act in the infection process. Staining techniques with fuchsine acid and fluorescence microscopy were employed. In the percentage of urediospore germination of wheat rust, there were no significant differences in multiple comparison of means (p>0.05; DMS). It was found, however, that Lalbahadur+Lr46 and Lalbahadur+Lr34 showed higher percentage of reduction (p≤0.05) in the germination percentage. With respect to the formation of apresoria, penetration, and substomatal bladder formation, significant differences (p≤0.05) between the genotypes Lalbahadur+Lr46 and Lalbahadur+Lr34 were noticed. In the tissues of rust-infected wheat leaf, cell damages were observed by the technique of inclusion in paraffin: collapse, cell disintegration, and necrosis. In the genotypes with gene Lr34, collapse, cell disintegration and finally necrosis were found all over the leaf with exception of the vascular bundle of genotype Lalb+Lr34 and to a great extent of the leaf in genotypes AOC+Lr34 and Jup73R+Lr34. The genotype with Gene 1 presented little necrosis at 86 h of sampling, that is why partial resistance was expressed soon, and in the genotype with gene Lr46, the infection began with collapse, followed by chloroplast disintegration at 30 h, and subsequently necrosis on the entire leaf except the vascular bundle, therefore its resistance became evident soon. Besides, papillae were detected in Jupateco 73R 40 h after inoculation. From the results obtained it is deduced that Lr34, Lr46, and Gene1 confer prehaustorial resistance, or in other words, before the haustorium of the fungus, which is very similar to the resistance of the non-host, that is of the durable type.

Keywords : Cell alterations; cereals; phyto-pathogens; vegetal resistance; signs.