Ralstonia solanacearum causes one of the most common soil-borne vascular diseases of diverse plant species, including many solanaceous crops such as tomato and pepper. The resulting disease, bacterial wilt (BW), is devastating and difficult to control using conventional approaches. The aim of this study was to investigate the differentially expressed genes in pepper root systems in response to infection by R. solanacearum. DNA microarray (Capsicum annuum 135K Microarray v3.0 Gene Expression platform) analyses were performed using a susceptible genotype, ‘Chilbok’, and a resistant genotype, ‘KC350’, at 3 time points (1, 3, and 6 days post inoculation). It has been identified 115 resistance-specific genes (R-response genes) and 109 susceptibility-specific genes (S-response gene), which were up-regulated in 1 genotype, but down-regulated in the other genotype. Gene Ontology (GO) analysis for functional categorization indicated that many R-response genes were related to genes that function in xyloglucan biosynthesis and cell wall organization, while S-response genes were involved in the response to stress and cell death. The expression of genes encoding xyloglucan endotransglycosylase/hydrolase (XTH) and β-galactosidase were verified by real-time RT-PCR at an early time point of R. solanacearum infection. The results supported the idea that rapidly induced XTH expression in ‘KC350’ may play an important role in the restructuring and reinforcement of the cell wall and restrict bacterial movement in xylem vessels. In addition, induced expression of β-galactosidase in R. solanacearum-infected ‘Chilbok’ implied that degradation of the cell wall structure in vascular tissues by β-galactosidase might be an important factor facilitating R. solanacearum invasion of and movement in susceptible host plants.

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The main characteristics (plant diameter, number of spine/areoles and length of spines) of 16 cactus hybrids were analysed and the genetic variability and broad-sense heritability was studied. The descendants were obtained through a cyclic crosspollination pattern, with the parental forms chosen based on aesthetic considerations. Cross-pollination among Rebutia senilis 9 Aylostera muscula, Rebutia tarvitaensis 9 Aylostera muscula, Aylostera flavistyla 9 Rebutia senilis, Rebutia senilis 9 Aylostera flavistyla, Aylostera muscula 9 Aylostera albiflora and Rebutia senilis 9 Aylostera albiflora did not succeed, whereas all of the other hand-pollinated crosses succeeded and produced viable seeds. The highest values of the analysed characters were observed in the progeny of A. fiebrigii var. densiseta 9 R. senilis and A. buiningiana 9 A. vallegardensis and the artificial selection to identify plants with special decorative traits was extremely efficient among them. In the F 1 population of the studied crosses, a large genetic diversity was found within hybrid combinations (families), between combinations and a different variation was recorded among the analysed traits. The broad-sense heritability ranged between 0.909 (plant diameter) and 0.948 (spines length). All of the characters analysed, in the present experience, have a strong genetic determinism, being greatly influenced by the genotype and to a lesser extent, by the cultivation conditions (greenhouse).

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decidua (European larch) has a scattered natural area and is present in four geographic zones (Alps, Sudetan Mountains, Carpathians, and Central Poland), where local European larch have sometimes the status of subspecies or varieties (Biswas and Mohri, 1997). In Romania, the larch has a natural range, being gathered into 5 genetic centers: Ceahlau Mountains (1400-1450 m altitude), Ciucas (1000-1450 m), Bucegi (1200-1500 m), Lotru Mountains (670-1900 m with a maximum range in this area), and Apuseni Mountains (600-1200 m), and in many other plantations more than 200,000 cultivated ha (Mihai and Teodosiu, 2009). The origin of seed is mostly unknown, but probably in the old plantation the seed has Austrian origin.Larch breeding objectives include growth, stem form (crookedness), branching, and resistance to larch canker. There is ongoing research for traits such as heartwood formation and quality (Plomion et al., 2001). Larch heartwood is appreciated for its good mechanical properties, its color, and its texture, and it is often used outdoors for its natural durability (Gierlinger et al., 2004).