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Food production worldwide is among the priorities of governments and institutions. The overall strategy for improving crop yields with less environmental impact, reduction of chemical application and preservation of biodiversity is geared towards sustainable agriculture. Resistant varieties are a tactic widely used in integrated pest management; thus breeding programs are a priority for achieving this goal. Understanding of the pathogens and the physiological bases, and the molecular and genetic interactions governing the plants may contribute to achieve durable resistance. In this complex scenario, a group of research works studying the interactions between hybrid Saccharum spp., Solanum lycopersicum L., Oryza sativa L., and different pathogens was developed at the National Center for Agricultural Health (CENSA), for over 25 years. The results are reported in this paper. [ABSTRACT FROM AUTHOR]

The lypoxigenase (LOX) expression, and the peroxidase and chitinase isoenzymes were studied for the first time in tomato leaves of several genotypes obtained in the different tomato plant breeding programs. The genotypes were healthy and they were inoculated with Alternaria solani isolates. Differentiation of varieties was better when the enzyme LOX was used compared with the other markers evaluated. Three fungus isolates from different regions of the country were used and the best results were achieved with the most aggressive isolate. The specific activity levels and the intensity of the bands obtained with LOX were higher in the plants inoculated of the resistant varieties compared with the susceptible ones suggesting that this protein could be related with the defense mechanisms in the interaction and constitutes a possible induced resistance marker. [ABSTRACT FROM AUTHOR]

Tobacco Mosaic Virus (TMV) is an economically important disease infecting crops worldwide. The objective of the present work was to evaluate the expression of representative sequences from N. tabacum genome in two Cuban tobacco varieties (BHmN and Corojo) with a different behavior in the pathogenic interaction. Leaf samples were taken at 0, 48 hours and seven days after virus inoculation to proceed with the total RNA extraction (Trizol method) and the primers were designed using sequences of tobacco defense genes to analyse their expression by RT-PCR. At seven days after inoculation, a β 1,3 glucanase expression was observed in both varieties, which was higher in the resistant one. Chitinase was induced at 48 h in the resistant variety with no expression seven days after inoculation. Phosphatase serine-threonine and the heat shock protein were expressed in both varieties at all the time tested; however the expression was a little higher in BHmN variety. In this study, the induction of β 1,3 glucanase in N. tabacum plants inoculated with TMV was likely to be related to the hypersensible response and the acquired systemic resistance. [ABSTRACT FROM AUTHOR]