Author : Amnouy Kamtuo

Summary : Eight accessions of passionfruit were crossed to produced an F1 generation. This was accomplished by crossing all possible combinations with reciprocal and sib-mating resulting into 64 crosses. In addition, sib-mating of F1 progenies were also done. Seven Fusarium isolates were collected in Rayong province and Khon Kaen University, Thailand. Out of these, four species of Fusarium were identified, namely: a) F. oxysporum, b) F. solani, c) F. fusariodes, and d) F. semitectum. One isolate of F. solani collected from Rayong province (FPR (subscript 2)) showed a high degree of pathogenicity on passionfruit. Segregation of progenies from F (subscript 1) lines showed no definite patterns to ascertain the number of genes controlling resistance to F. solani. However, it was found that incubation period plays a major role in the expression of resistance to F. solani. Furthermore, it can be deduced that resistance was controlled controlled by multiple genes and maternal influence. The latter is exemplified by when P. edulis (PNG) is used as female parent. Generally higher heritability estimates were obtained on all accessions when used as female. Resistant plants, both infected and uninfected with F. solani, exhibited different morphology on its stem base compared to that of uninfected susceptible plant. A thick-walled cell appeared between cortex and vascular cambium, which formed into continuous cylinder cells, is present. This was the result of the gelation formation in vascular fiber cells, which acts as a pre-existing morphological mechanism to prevent the mycelium of F. solani in invading and gaining access to the vascular system. Results obtained from the extraction and separation phenolic compounds using thin layer and gas-liquid chromatography showed that there was no difference and biochemical units within resistant lines, both infected and uninfected; and uninfected susceptible lines with F. solani. This indicates that phenolic compounds and cyanogenic glycosides does not play a major role.