Ultrastructural Studies of the Mode of Penetration by Phoma macdonaldii in Sunflower Seedlings.

ABSTRACT An ultrastructural investigation of the artificial inoculation of sunflower with Phoma macdonaldii conidia was undertaken using light, scanning, and transmission electron microscopy to elucidate the host-parasite relationship. The behavior of the conidia deposited on the cotyledon petiole was investigated at various time intervals after inoculation. Conidia adhesion and germination were observed first.

Study of interaction between plant nutrition (N,P,K and Ca) and verticillios wilt disease (Verticillium dahliae) in cucumber.

Cucumber wilt disease caused by verticillium dahliae is one of the most important diseases of cucumber. Disease severity can to be decreased by plant nutrition management, especially nitrogen, phosphorus, potassium and calcium levels. For this purpose, interaction between plant nutrition and cucumber verticillios disease in cucumber was studied.

A QTL analysis of sunflower partial resistance to downy mildew ( Plasmopara halstedii) and black stem ( Phoma macdonaldii) by the use of recombinant inbred lines (RILs).

Partial resistance to downy mildew ( Plasmopara halstedii) and to black stem (Phoma macdonaldii) in sunflower were investigated under natural field infection and a controlled growth chamber respectively. Genetic control for resistance to the diseases was determined in recombinant inbred lines (RILs) and their two parents, 'PAC-2' and 'RHA-266.' The experiments were undertaken in a randomized complete block design with two replications, in a field severely infected by downy mildew and in a controlled growth chamber with plants inoculated with an agressive French isolate of P.