Abstract: Three different resistant tomato lines ( Inbred line 5, CLN2037E and their cross F₁ ) were stud
ied in incubator after inoculating Phytophthora infestans. We took leaves at different time to observe the deterio
ration of leaves ultra structure. The result showed that: first, before inoculating Phytophthora infestans, Inbred
line 5 hasmore mitochondria than F₁ and CLN2037E. Second, inoculated 42 h, three lines appeared p lasmoly
sis. Both Inbred line 5 and F1 appeared peroxisome and the mitochondria quantity increased, and chlorop last of
Inbred line 5 was also damaged. Third, inoculated 54 h, CLN2037E appeared peroxisome and mitochondria
quantity increased; also a part of chlorop last of F₁ was destroyed. Fourth, inoculated 72 h, the cell wall in all
three lines became creased. Much of the chlorop lastmembrane of inbred line 5 was decomposed. There was only
scattered thylakoid and grana lamella, a few mitochondria cavitations and membrane was damaged. There was
basic chlorop last structure in F₁ and little chlorop last membrane of CLN2037E was damaged. Conclusion: we
compared resistant line (CLN2037E) with sensitive line ( Inbred line 5) after inoculating Phytophthora infes
tans, and found that the structure of resistant line chlorop lastwas least damaged. Peroxisome appeared later and
increased quantities ofmitochondria also appeared at later stage. Creasing in the cell wall became obvious.

Key words: Tomato, Leaf, Phytophthora infestans, Ultra structure