Sixteen tomato [Solanum lycopersicum L. (syn. Lycopersicon esculentum Mill.)] genotypes (inbred lines or hybrids) were tested against five Phytophthora infestans (Mont.) deBary isolates to characterize race specificity of late blight resistance transferred to tomato from Solanum pimpinellifolium L. [syn. Lycopersicon pimpinellifolium (L.) Mill.] accession L3708. The effects of plant genotype, isolate, genotype × isolate, and isolate × replication interactions were highly significant (P = 0.001). Set of four sister lines fixed for late blight resistance (CU-R lines) exhibited full and equal resistance to the five pathogen isolates tested. In contrast, the heterozygous F1 hybrids, created by crossing the resistant CU-R lines with a susceptible parent, were resistant to US-11; partially resistant to US-17, NC-1, and DR4B; and susceptible to US-7. Differential responses were also observed across pathogen isolates on a set of resistant sister lines (CLN-R lines), which also were bred from L3708. The CLN-R lines were resistant to the DR4B, NC-1, and US-11 isolates, but showed significant disease-affected areas and sporangium numbers following inoculation with either US-7 or US-17. Restriction fragment length polymorphism (RFLP) analysis confirms that both CU-R and CLN-R are homozygous for the Ph-3 gene derived from L3708. Since progeny tests also confirmed that the CLN-R lines are fixed for their level of resistance, these results suggest that late blight resistance in the CU-R lines is not controlled by Ph-3 alone, and that at least one additional gene conferring late blight resistance is missing from the CLN-R lines. Results of genetic tests of the (CU-R × CLN-R) F1 and a (CU-R × CLN-R) F2 population with the pathogen isolate US-17 strongly support a model in which resistance of the CU-R lines requires genes in addition to Ph-3. The implications of this information in breeding for late blight resistance and using of the resulting resistant lines or hybrids are discussed.
Late blight [caused by Phytophthora infestans (Mont.) de Bary] causes severe loss of tomato [Solanum lycopersicum L. (formerly Lycopersicon esculentum Mill.)] production in environments favorable to the pathogen. Researchers at the Asia Vegetable Research Development Center (AVRDC) identified resistance to late blight in an accession of S. pimpinellifolium [formerly L. pimpinellifolium (L.) Mill.] that they named accession L3708. This resistance has now been transferred to processing tomato lines, which are resistant to multiple P. infestans isolates. Lab trials, inoculated field trials in New York, and naturally infested field trials in Mexico all indicate that these processing tomato lines are fixed for late blight resistance. Segregation data obtained for resistance in the breeding populations were dependent on the pathogen isolate used for the disease screen. Segregation data do not support the hypothesis of single gene control of the full resistance trait, but instead suggest that more than one gene is involved, and that these genes interact in an epistatic manner.
This experiment was carried out to select resistant cultivar to CMV in cucumber using Elisa-test and protoplast isolation method. Twenty domestic cultivars or lines and 8 European cultivars were ested for resistance by Elisa test. Among the domestic cultivars, DADAKI group was found to be susceptible and CHEONGJANG group resistant. Among all the cultivars and lines tested, a European cultivar, DALIBOR and Janghyungheukjinju Korean line were found to be highly resistant. When comparing for the protoplast yield depending upon the positions of seedlings (cotyledon, young leaf and hypocotyl), the highest protoplast yield could be obtained from cotyledons in macerozyme 0.5% + cellulose 2.0%. Protoplast yields in susceptible cultivars were higher than those from resistant cultivars. Differences in cell wall thickness between susceptible and resistant cultivars were observed.