Plants Diseases

Plants Diseases 

    Many diseases are produced in the plants these are very harmful for plants. Some diseases are  destroy the crops. These disease like rust, smut. Some of these diseases are given below. 

Ustilago (Smut) 

    Ustilago is parasite on the grasses like wheat. It is commonly called smut. It attacks on the overies of grasses. Some time it completely destroy the whole ears of wheat plants. Different types of Ustilago effect the different plant. Some of these are Ustilago tritici which effect the wheat plant.Oat plant is effected with Ustilago avenae. Ustilago zea attacks on maize. Structure of smut. Mycelium of Ustilago composed monokaryotic and dikaryotic hyphae. The hyphae is septate. The primary mycelium is monokaryotic. It is short lived and does not grow much. Secondary mucelium is dikaryotic. Mycelium is intracellular or extracellular.

Effecting of Ustilago

       It has different ways of ustilago effecting the plants. Ustilago attacks on the mature wheat plant in spring. Ears of wheat are produced in this season. The ears in the diseased plants are emerge earlier than the healthy plants. These ears are covered with black powdery mass. This powdery mass great Chlamydospores  or Teleuto spores.Each spore is unicellular and binucleate. It is thick wall.

Effects with formation of promycelium

        Chlamydospores are dispersed by wind. They fall on the ears of healthy plants. They germinate on the ear. Their nuclei fuse to form diploid zygote nucleus. The zygote nucleus is undergoes meiosis. The spore are produces a short germ tube or promycelium (primary mycelium). Basidiospore  Each cell of promycelium produce a sterigma. Basidiospre are produced on the sterigma.  

Puccinia  ( Rust)

       Rust is large genus. It has several obligatory parasitic species. Puccinia graminis  has many form. Each form specific host. They are parasite in wheat, corn, barely and rye etc. Puccinia tritici is parasite of wheat. It completes its life cycle in two different hosts wheat and barely. It is hetercious rust.Rust attacks in different stages. These stages are five in number. First stage in Uredinial stage Its infection is appear in March. Reddish brown pustules or sori is appear on the stem of wheat. These sori named as uredosori. Uredosori contain numerous uredospores. These are globose and thick walled spores and borne on the long stalks. Telial stage is second stage of  rust. These spore are produced in the end of growing season. Some hyphae develop teleutospore. The colour of these spore is dark red or rusty. These spore are oval in shape with tapering ends. They have constriction in the middle. Teleutospore are not grow immediately.

     Basidial stage Teleutospore  germinates in the next spring on the soil. Each teleutospore produce a germ tube called promycelium. Two nuclei of each cell fuse to form diploid nucleus.Pycnial Stage Haploid basidiospores  infect second host barberry. They fall on the leaf of barberry. They germinate to produce a small germ tube. The germ tube penetrates the cuticle and enter epidermal cell of leaf. Aecial stage is last stage. Soermatium attach on the receptive haypha of opposite sexual strain. Its nucleus migrate into hyphae through receptive tube

Other Virus of Plants 

Tobacco Mosaic virus   TMV is RNA virus. Its capsid is coiled and rod shape. It attacks on stem and leaves. In there attack leaves become wrinkle and molds. These mosaics are present  in   the   form   of   light   green  spots.  These  spots  become  narrow  and  stunted. 

Mosaic virus  of cucumber and lettuce    Virus also causes in the cucumber and lettuce   plants.    These   viruses   are  mostly   spread   by   pest   like   aphids   and   leaf   hoppers.

Cotton leaf curl virus or  LCV   This virus attacks on cotton plants. It caused huge cotton losses in different countries.  LCV is spread by white fly named Bemisia tabaci. 

Diseases of some other virus


       Virus cause many disease. Yellow disease of Potato It is caused by infectious particle called viroid. The tomato plant fell down wilt and become dry. Necrotic diseases In this disease virus kills the leaf of plant by necrosis. This disease occur in potato and tomatoes. Tumors  Many virus cause tumors in tomato cucumber and tobacco plants.