Four Fungi and an oomycete associated with heavily leaf blight-infected cucumber (Cucumis sativus L.) plants in Calinan, Davao City /
John Roy T. Andoque
- 2010
- 34 leaves.
Thesis (BS Biology) -- University of the Philippines Mindanao, 2010
Cucumber gardens in Calinan, Davao City were seriously hit by a leaf blight disease syndrom characterized by an array of symtoms manifested on the foliage such as powdery mild dew, downy mildew (angular spots) and circular spots. Fruit demormity and rot on infected plants were also commonly observed, attributed apparently to the heavy leaf infection. Preliminary assessment on the range of disease symptoms and its corresponding pathogens was initiated to serve as benchmark information for future disease managementstudies. Conidia scraped from the infected leaf surface were observed in vivo. Keys of Barnett and Hunter (1972 and several related studies suggested three fungi to be Bipolaris sp., Septoria sp., and Fusarium sp., and the fourth fungus to be Podosphaera sp., based on Zitter (1992) associated with the disease syndrome.Poroconidia of the genus Bipolaris, measuring 125.68 um (60.02um) x 11.78 um3.62 um), was found abundant on circular spots. Septoria sp. with conidia measuring 86.14um (56.98um) x 3.23 um (1.59 u,) was frequented on blight. Podosphaera sp. conidia, measuring 28.82 um (2.47 um) long and 18.32 um (1.47um) wide, were found highly associated with white powdery growth symptom. Fusarium sp., which produces macronidia that are 26.96 um (9.27um) 4.02 um (0.63 um), was found to be abundant on fruit rot.An oomycete, Pseudoperonospora sp., was identified through keys from Stover (1930) and Walker (1930) complemented by a report of Choi and Shin (2006). Its conidia, measuring 29.72 um ( 4.29um) long and 18.59 um (1.73 um) wide was predominant on angular spots. Pathogenicity tests should be done on then recorded fungi and oomycete to confirm their pathogenic association with the host.