ICAR-IARI Technician flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Extension teaching elements

Leagans listed teacher, learner, subject matter, teaching methods and materials, and environment as the interacting elements of any extension teaching-learning situation.

Adopter categories

Rogers classified adopters as innovators, early adopters, early majority, late majority and laggards based on time of adoption, using mean and standard deviations of adoption time.

Result demonstration

A demonstration conducted under farmer conditions comparing an improved practice with the local practice, designed to convince farmers by showing results rather than merely telling them.

Method demonstration

A group teaching method in which the extension worker shows step by step how a practice is performed, so learners acquire a skill such as seed treatment or pruning.

Formative versus summative evaluation

Formative evaluation is done during a programme for mid-course correction; summative evaluation is done at the end to judge whether stated objectives were achieved.

Diffusion of innovation

Diffusion is the social process by which an innovation spreads through members of a social system over time via communication channels, distinct from the individual adoption decision.

Extension programme planning

The sequence of collecting facts, analysing the situation, identifying problems, setting objectives, preparing a plan of work, executing it and evaluating the results.

Mass contact methods

Extension methods reaching many people quickly with limited personal contact, including radio, television, newspapers, leaflets, exhibitions and campaigns; they create awareness rather than teach skills.

Backcross method

A breeding method that transfers a specific gene, commonly disease resistance, into an otherwise superior recurrent parent through repeated backcrossing with selection for the donor trait.

General combining ability

GCA is the average performance of a line in crosses with a set of testers; it reflects additive gene action and is estimated by top cross or polycross tests.

Narrow-sense heritability

The ratio of additive genetic variance to total phenotypic variance; it predicts the response of a population to selection and is more useful to breeders than broad-sense heritability.

Heterobeltiosis

Heterosis measured as the superiority of the F1 hybrid over its better parent; standard heterosis compares the F1 with a commercial check variety instead.

Seed certification classes

Breeder seed, foundation seed, registered seed and certified seed form the certification chain; each class has prescribed genetic purity standards and generation limits.

Pedigree method

A selection method for self-pollinated crops in which individual plants are selected from segregating generations and their progeny are tracked with pedigree records until uniform lines are fixed.

Mutation breeding mutagens

Physical mutagens include gamma rays, X-rays and fast neutrons; chemical mutagens include EMS and sodium azide; induced mutants are usually recessive and need selfing to express.

Synthetic variety

A variety produced by intercrossing several selected parental lines and harvesting the bulk progeny; it exploits general combining ability and can be reconstituted from the parental lines.

Economic threshold level

The pest population density at which control measures should be applied to prevent the pest from reaching the economic injury level, where crop loss equals control cost.

Koch's postulates

Rules proving a pathogen causes a disease: consistent association, isolation in pure culture, inoculation into a healthy host reproducing symptoms, and re-isolation of the same organism.

Bacterial wilt pathogen

Ralstonia solanacearum causes bacterial wilt of tomato, potato, brinjal and other solanaceous crops, showing sudden wilting with vascular browning and bacterial ooze.

Citrus canker pathogen

Xanthomonas citri causes citrus canker, producing raised corky lesions with yellow halos on leaves, stems and fruits; it spreads through rain splash and infected planting material.

Protectant versus systemic fungicide

Protectant fungicides such as mancozeb prevent infection when applied before the pathogen arrives; systemic fungicides such as carbendazim are absorbed and act after infection.

IRAC mode-of-action rotation

Insecticide resistance management rotates products from different IRAC mode-of-action groups and preserves refugia to reduce selection pressure on the pest population.

Lesser grain borer

Rhyzopertha dominica is a serious stored-grain pest of cereals whose larvae and adults bore into grains, leaving frass and reducing weight and germination.

ELISA for plant viruses

Enzyme-linked immunosorbent assay detects plant viruses by antibody binding in a sample; it is used alongside symptom observation and PCR for reliable virus diagnosis.

Calvin cycle

The light-independent phase of photosynthesis in the stroma, where rubisco fixes CO2 into 3-phosphoglycerate using ATP and NADPH produced by the thylakoid light reactions.

C4 photosynthesis

C4 plants such as maize and sugarcane fix CO2 first with PEP carboxylase in mesophyll cells, concentrating CO2 around rubisco and greatly reducing photorespiration.

Aerobic respiration ATP yield

Complete oxidation of one glucose molecule yields about 36 to 38 ATP, from glycolysis in the cytoplasm and the Krebs cycle plus oxidative phosphorylation in mitochondria.

Cation exchange capacity

CEC is the total exchangeable cations a soil can hold per 100 g, expressed in cmol(p+)/kg; it increases with clay content and organic matter and buffers nutrient supply.

Liebig's law of minimum

Crop yield is limited by the essential nutrient present in shortest supply relative to requirement, regardless of the adequacy of other nutrients in the soil.

Water potential equation

Water potential equals solute potential plus pressure potential plus gravitational potential; water moves from higher to lower water potential, and turgor pressure is the positive component.

Dihybrid F2 ratio

A cross between two individuals heterozygous at two independently assorting loci gives an F2 phenotypic ratio of 9:3:3:1, and a test cross gives 1:1:1:1.

Parts per million conversion

In dilute aqueous solutions 1 ppm equals 1 mg per kg or 1 mg per litre, and 1 percent equals 10,000 ppm; these conversions are used in spray and nutrient calculations.