Plant Pathologist's Diary: Practical 4 Protozoa (Phylum Plamodiophoromycota), Hromista (Oomycota) and Lower Fungi (Phyla Chytridiomycota & Zygomycota)

INTRODUCTION

Protozoa, Chromista and lower fungi are considered as being the least developed among fungi and fungal-like microorganisms. The body of members is either plasmodium, while those that produced mycelium have hyphae that are coenocytic (non-septate). Asexual production forms spores such as zoospores (motile) and sporangiospores (non-motile), and sexual production yields resting spores such as oospores and zygospores. Many microorganisms in this group cause serious plant diseases.

OBJECTIVES

1. To study the taxonomy and pathological importance of protozoa, chromista and lower fungi.

2. To learn the characteristic shown by each of the fungi and fungal-like microorganism.

3. To observes the disease cycles of various fungal-like organisms and fungi.

METHODS

This laboratory displayed cultures and slides of protozoa, chromista and lower fungi and the speciments of plant diseases that they cause. The cultures and slides was study to differentiate these fungi and fungal-like microorganisms based on morphological features and symptoms of disease caused.

RESULT AND DISCUSSION

A. FUNGAL CULTURE

Pure cultures	Phytophthora sp	Pythium sp	Rhizopus sp
Slides
Colour	Blue	Brownish	Brownish
Hypal characteristic	- Non septate hyphae	- Non septate hyphae	- Branching hyphae
Shape of sporangium	- Round with thick wall, Zoospores in zoosporangia	- Spherical sporangia-like structures, Round with thick wall	- Spherical sporangia-like structures, Round with thick wall

B. PLANT DISEASE SPECIMENS

DISEASE	MICROORGANISMS	EXPLANATION
Club root disease	Plasmodiophora brassicae	Infects cruciferous vegetables such as cabbages. Main symptom of hypertrophy (enlargement) of roots.

Shoot or flower blight	Choanephora cucurbitarum	Infects chilli and various solanaceous crops such as brinjal and okra. Symptom include leaf defoliation, fruit and shoot rot.
Damping off of seedlings	Pythium sp	Attack mainly seedlings. Damping off during pre-germination causes seed rots. Post germination damping off causes rots on the stems and roots of seedlings usually closes to soil level.
Potato late blight	Phytophthora infestans	Infects potato leaves, stem and tubers. Symptoms of black lesion.
Black pod	Phythophthora palmivora	Infects cocoa pods during wet weather. Symptoms of black lesions causing pods to rot within a day.