We studied DNA degradation and nuclear fragmentation during programmed cell death (PCD) in petals of Ipomoea nil (L.) Roth Xowers. The DNA degradation, as observed on agarose gels, showed a large increase. Using DAPI, which stains DNA, and Xow cytometry for DAPI Xuorescence, we found that the number of DNA masses per petal at least doubled. This indicated chromatin fragmentation, either inside or outside the nucleus. Staining with the cationic lipophilic Xuoroprobe DiOC 6 indicated that each DNA mass had an external membrane. Fluorescence microscopy of the nuclei and DNA masses revealed an initial decrease in diameter together with chromatin condensation. The diameters of these condensed nuclei were about 70% of original. Two populations of nuclear diameter, one with an average diameter about half of the other, were observed at initial stages of nuclear fragmentation. The diameter of the DNA masses then gradually decreased further. The smallest observed DNA masses had a diameter less than 10% of that of the original nucleus. Cycloheximide treatment arrested the cytometrically determined changes in DNA Xuorescence, indicating protein synthesis requirement. Ethylene inhibitors (AVG and 1-MCP) had no eVect on the cytometrically determined DNA changes, suggesting that these processes are not controlled by endogenous ethylene.

No abstract

Resistance to Fusarium oxysporum f.sp. melonis race 2 is conferred by a single dominant gene, Fom-1 in melon. Here, we identiWed DNA markers tightly linked to Fom-1 that could be used for marker assisted selection in breeding programs. First, we developed 125 F 2 plants derived from the cross between melon lines P11 (fom-1fom-1) and MR-1 (Fom-1Fom-1). Using the F 2 population, we constructed a linkage map including 14 SSR markers which had not been mapped previously. Fom-1 was conWrmed to be allocated to linkage group 7. Then, we identiWed four AFLP markers using bulked segregant analysis. The AFLP marker TAG/GCC-470 was completely linked to Fom-1 and other three markers were mapped near Fom-1. TAG/GCC-470 and TCG/GGT-400 were respectively converted to STS and CAPS markers. Usefulness of DNA markers was conWrmed in the analysis with several melon cultivars and lines.

No abstract

No abstract