eChapters

Genetic variations

Genetic variation is the presence of differences in gene sequences between individual organisms of a species.

Enables natural selection, one of the major forces driving the evolution of life.

When an individual’s offspring exhibit mutations in the traits of their parents, such offspring are called variants.

1. Markers: Easily identifiable features are called markers or marker features.

2. Types of marker

These markers are three types

2.1.Morphological markers: These relate to the size, shape, color and surface area of different parts of the plant.

2.2.Biochemical markers: Such markers refer to changes in protein structure. For example, isozymes and storage proteins.

Disease Control vs. Disease Management

The word control evokes the notion of finality, the final elimination of problems .

It is impossible to exclude , eliminate or prevent diseases.

Control is ecologically and practically not possible.

Although disease control is an established and widely understood concept, there are compelling reasons to replace control with management .

Changes in philosophy about plant disease management

To achieve reasonable and sustainable results crop disease management philosophy should shift focus from

Management of pathogens (or insect vectors) to managing host plants.

A single goal of high productivity to multiple goals of high yield, efficiency, quality and safety.

Introduction

It is becoming increasingly difficult to find workers to work in agriculture.

Younger generations do not want to work in plant protection.

We can see that the average age of farmers is getting older.

This leaves the fields unprotected from disease and insects and greatly reduces yields.

Fortunately, this gloomy situation has changed since 2015 thanks to modern technology.

Digital tools are among the most innovative crop protection tools in modern agriculture.

Aim: To verify the relationship between the input and output voltage for 3-phase transformer connection in various ways:

A 3-phase transformer can be considered as a set of 3 single-phase transformer bank or as single unit of 3 phase windings. Since three winding are available in both primary and secondary side then there can be different types of connections and so far, different characteristics.

Aim: To determine the Load characteristics (External characteristics) of self excited D.C. shunt generator.

If a dc shunt generator, after building up to its voltage, were loaded, its terminal voltage will drop. This drop increases if load increases. But this type of terminal drop is undesirable for a specified service. The relation between terminal voltage and load current is called external characteristics. Speed is to be kept constant. Reason for voltage drop:

Aim: To perform speed control of D.C. shunt motor by

1. Armature resistance control method.

2. Field (flux) control method.

This method is based on the fact that by varying the voltage available across the armature, the back EMF and hence the speed of the motor can be changed. This is done by inserting a variable resistance RC (known as controller resistance) in series with the armature as shown in Fig. (a).

Aim: Determination the equivalent circuit parameters of a single-phase induction motor.

1. No-load test.

2. Blocked rotor test.

The performance of a single-phase induction motor is generally studied either by double revolving field theory or by cross field theory, the former being simple and gives a clear physical understanding.

Aim: Perform an experiment to determine the parameters of a three-phase induction machine.

As the circuit modal of an induction motor is similar to that of a transformer, the parameter of the modal can be obtained by no-load test and blocked rotor test.

No-load test

In this test, the motor is to run at no-load at rated voltage and frequency. The applied voltage and current and power input is measured. Power input at no load (Po ) provides only the losses that are rotational losses.

Aim: To study the effect of variation of field current upon the stator current and power factor with synchronous motor running at no-load, hence to draw V and inverted V curves of the motor.

With constant mechanical load on the synchronous motor, the variation of field current changes the armature current drawn by the motor and also its operating power factor. As such, the behavior of the synchronous motor is described below under three different modes of field excitation.

About the Lower Bhavani Project

The Lower Bhavani Project (LBP) is located in Tamil Nadu in Bhavani River, irrigates 83980 ha in two seasons in a year. The canal water supply is provided for one wet crop from August to December (41885 ha) and one dry crop from January to April (41885 ha). The cultivated area under LBP in Erode and Coimbatore districts are irrigated lands with canals and groundwater, and rainfed crop lands (with supplemental groundwater irrigation).

Participatory curriculum development (PCD) in extension education is an emerging approach to help and improve the quality of education in farm universities. The main steps of the PCD approach adopted here have high practical utility for the design of formal course contents for the Undergraduate and Postgraduate courses in Agricultural Extension. A great deal of thinking is required while deciding on how much participation will be required from which stakeholders, at what level(s).

As stated before, a careful assessment of the existing curriculum is essential before any modification is undertaken and must take into account the country’s education policy, political, economic, demographic, cultural, social and technological environment. Problems of farmers to be solved, needs to be satisfied, and priorities to be identified and addressed and then only the recommendations made for action.

• Content approach

We can identify several different ‘traditional’ approaches to curriculum development. The most common approach until recently is the ‘content’ approach. This is where the curriculum is basically a list of knowledge – things that the agricultural graduating learners need to know. Usually this list is made by a curriculum development committee or group of experts identified at the national level.

In the present system of curriculum changes, participation of all the stakeholders are not actively involved in developing curriculum over the years.

The motive behind conducting the workshop on Capacity Need Assessment and Development is that the existing Extension Advisory Services (EAS) needs new capacities to respond effectively to the emerging challenges in agricultural development.

The results of Focus Group Discussions and Field Level Workshops (Tables presented at the end of toolkit) conducted with different stakeholders mentioned in the methodology revealed that, communication skills, soft skills, leadership development skills, personal and professional development skills followed by entrepreneurship development skills are more important and needed to perform job effectively at field level extension work (Table 1).

The concept of capacity development is defined in various ways. Broadly, it is defined as a process by which skills, and knowledge are built, utilized, retained and nurtured with a view to provide an entity responding to a development challenge. Two components that are vital in any plausible definition of the concept are human skills (the ability to perform a task) and institutions (effectiveness and efficiency of organizations, systems, processes and procedures).