ICAR-IARI Technician cheat sheet

Extension education is defined as the process of bringing about voluntary behavioural change in rural people through education, not coercion or subsidy delivery alone.

Leagans' elements of the extension teaching-learning situation: the teacher (extension worker), the learner (farmer), the subject matter, the teaching methods and materials, and the physical and social environment.

Communication model used in extension: sender → message → channel → receiver → feedback; noise is any factor that distorts the message between source and receiver.

Adoption decision process (Rogers): knowledge → persuasion → decision → implementation → confirmation; adoption is the mental process, diffusion is the social process.

Adopter categories by innovativeness: innovators (first ~2.5%), early adopters (~13.5%), early majority (~34%), late majority (~34%), laggards (~16%), based on mean plus standard deviations of time of adoption.

Teaching methods: individual contact (farm and home visit, office call, telephone call), group contact (method demonstration, result demonstration, lecture, field day, group meeting), and mass contact (radio, TV, print, exhibition, campaign).

Result demonstration shows the superiority of a practice over the local practice under farmer conditions; method demonstration teaches the skill of doing a practice step by step.

Extension programme planning steps: collection of facts, analysis of the situation, identification of problems, determination of objectives, plan of work, execution, and evaluation.

Evaluation types: formative (during the programme, for mid-course correction) and summative (at the end, to judge outcome); both measure progress against stated objectives.

Mendel's law of segregation applies to a single gene pair; the law of independent assortment applies to two or more gene pairs on different chromosomes.

Self-pollinated crops are improved mainly by pureline selection, pedigree method, bulk method and backcross method; cross-pollinated crops rely more on mass selection, recurrent selection and synthetic or composite varieties.

Backcross breeding transfers one or a few genes (often disease resistance) into a recurrent parent; six or more backcrosses are needed to recover the recurrent parent phenotype, with selection for the donor gene each generation.

Heterosis is the superiority of F1 over the better parent (heterobeltiosis) or over the standard check (standard heterosis); it is exploited commercially in maize, sorghum, pearl millet, cotton, castor and sunflower.

Combining ability: general combining ability (GCA) reflects additive gene effects and is tested by top cross or polycross; specific combining ability (SCA) reflects non-additive effects and is tested by line × tester or diallel analysis.

Heritability in broad sense = VG/VP; narrow sense = VA/VP, where VA is additive variance; only narrow-sense heritability predicts response to selection, and response R = i × h² × σP.

Gene action: additive variance is fixable in pure lines; dominance and epistasis are non-fixable and best exploited through hybrids; Griffing's diallel methods partition variance accordingly.

Mutation breeding uses physical mutagens (gamma rays, X-rays, fast neutrons) or chemical mutagens (EMS, sodium azide); induced mutants are often recessive and require selfing to express.

Seed certification classes in India: breeder seed, foundation seed, registered seed and certified seed; the genetic purity standard for certified seed of most self-pollinated crops is 99.0%.

Economic threshold level (ETL) is the pest density at which control measures must be applied to prevent the pest from reaching the economic injury level (EIL), the density causing crop loss equal to control cost.

IPM hierarchy: cultural, mechanical, physical, biological, botanical and chemical methods; chemical control is the last resort, applied on ETL basis.

Koch's postulates establish pathogenicity: the organism must be consistently associated with the disease, isolated in pure culture, inoculated into a healthy host to reproduce symptoms, and re-isolated.

Fungal disease signs: mycelium, conidia, sporangia, sclerotia, rust pustules (uredinia), and powdery or downy growth; bacterial diseases show water-soaked lesions, oozing and no fungal structures.

Bacterial wilt of solanaceous crops is caused by Ralstonia solanacearum; citrus canker by Xanthomonas citri; bacterial blight of rice by Xanthomonas oryzae pv. oryzae.

Viral diseases are diagnosed by symptoms, vector transmission and serology (ELISA) or PCR; most plant viruses are transmitted by aphids, whiteflies or thrips in a non-persistent, semi-persistent or persistent manner.

Fungicide groups: protectants (mancozeb, chlorothalonil) act before infection; systemic fungicides (carbendazim, propiconazole) act after infection; resistance management requires rotation among modes of action.

Insecticide resistance management relies on mode-of-action rotation, refugia, and avoiding repeated use of the same IRAC group; resistance is heritable and selected by repeated exposure.

Important storage pests: Sitophilus oryzae (rice weevil), Rhyzopertha dominica (lesser grain borer), Tribolium castaneum (red flour beetle) and Callosobruchus chinensis (pulse beetle).

Photosynthesis: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O; light reactions occur in thylakoids producing ATP and NADPH, and the Calvin cycle fixes CO2 in the stroma via rubisco.

C3 plants fix CO2 to 3-phosphoglycerate and photorespire; C4 plants (maize, sugarcane) use PEP carboxylase and have low photorespiration; CAM plants (cacti, pineapple) fix CO2 at night.

Respiration: glycolysis in cytoplasm (net 2 ATP, 2 NADH), Krebs cycle in mitochondria, and oxidative phosphorylation yielding about 36-38 ATP per glucose under aerobic conditions.

Soil pH affects nutrient availability: N, P, K are most available near pH 6.0-7.0; Fe, Mn, Zn and Cu become deficient at high pH; Al and Mn become toxic at low pH.

Law of minimum (Liebig): yield is limited by the nutrient in shortest supply; law of diminishing returns applies to increasing fertilizer doses beyond the optimum.

Cation exchange capacity (CEC) is the sum of exchangeable cations held per 100 g soil, expressed in cmol(p+)/kg; it rises with clay and organic matter content.

Mendelian genetics: monohybrid F2 ratio is 3:1, dihybrid F2 ratio is 9:3:3:1, and test cross ratios are 1:1 and 1:1:1:1 respectively.

Water potential (ψw) = ψs + ψp + ψg; water moves from higher to lower water potential, and turgor pressure is the positive component that keeps cells rigid.

Common laboratory values: 1 ppm = 1 mg/kg = 1 mg/L in dilute solutions; 1% = 10,000 ppm; N × 6.25 approximates crude protein content of a feed or grain sample.