Ch 9Plant Breeding — Class 12 Botany, concept-first.

Before looking at how humans and plants have interacted through history, the chapter frames the whole subject as economic botany — the study of the relationship between people and the plants that matt…

From the very earliest times, human beings have co-existed with plants, which played a vital role in their survival.

Domestication is the deliberate process by which a wild plant species is brought under human control and gradually reshaped — through careful selection, genetic alteration and everyday handling — into…

The oldest archaeological evidence of agriculture comes from the Fertile Crescent — the region around the Tigris and Euphrates river valleys in present-day West Asia — dating back roughly 12,000 years…

The scientific understanding of where and how crop plants originated developed over more than a century of study by different scholars.

Organic farming is an alternative agricultural system that emerged in the early twentieth century as a reaction against the rapid changes taking place in mainstream farming practice.

Biofertilizers are preparations containing living or latent cells of efficient microbial strains that help crop plants take up nutrients through their interactions in the root zone (rhizosphere) when…

Rhizobium bio-fertilizer culture consists of preparations containing Rhizobium bacteria, which live symbiotically inside root nodules that form on the roots of leguminous plants (Figure 9.4).

Azolla is a small, free-floating water fern that lives in symbiosis with the nitrogen-fixing blue-green alga Anabaena azollae, housed within cavities on its fronds.

Arbuscular mycorrhizae (AM) form through a symbiotic association between certain phycomycetous (zygomycete-type) fungi and the roots of flowering plants.

Seaweed liquid fertilizer (SLF) is produced mainly from kelp, a brown alga that can grow up to 150 metres long (Figure 9.7), and it supplies plant hormones — cytokinins, gibberellins and auxin — along…

Bio-pesticides are biologically derived agents used to control plant pests, valued for being non-toxic, cheaper and more eco-friendly than chemical or synthetic pesticides, and they have become an imp…

Green manuring is the practice of growing green manure crops and ploughing them directly into the field, mainly to raise the soil's nitrogen content while also improving its structure and physical pro…

Plant breeding is the science of improving crop varieties so that they yield more, are of better quality, resist disease, and mature in a shorter time suited to their growing environment.

Plant breeding programmes are designed around a consistent set of goals: increasing the yield, vigour and fertility of the crop; improving its tolerance to environmental stress such as salinity, tempe…

A plant breeding programme follows a broadly consistent sequence of stages, summarised in Figure 9.11.

Conventional plant breeding methods — those developed and refined over decades before the arrival of modern biotechnology — have had an enormous impact on agricultural productivity, mainly through the…

Plant introduction is the process of bringing a genotype from the place where it is normally grown into a new place or environment — for instance, the rice variety IR8 was introduced into India from t…

Selection is the choice of individuals from a mixed population that carry one or more desirable traits, and it is the oldest and most basic method of plant breeding.

Hybridisation is the deliberate crossing of two or more genetically dissimilar plants to produce a progeny called a hybrid, and it remains the single most effective way to combine desirable characters…

Heterosis, or hybrid vigour, is the superiority an F1 hybrid shows in performance over both its parents — G. H. Shull first used the term in 1912.

Mutation breeding, a term coined by Muller and Stadler (1927–1928), improves a crop by correcting a specific defect without sacrificing its existing agronomic and quality characters — mutation here me…

Most flowering plants are diploid, carrying two sets of chromosomes (2n); polyploids are plants that carry more than two sets, and polyploidy is a major evolutionary force in both wild and cultivated…

The term Green Revolution was coined by William S. Gaud in 1968 to describe the cumulative outcome of a series of research, development, innovation and technology-transfer efforts that dramatically ra…

Hybridisation and selection have been used to release many crop varieties bred specifically for resistance to fungal, bacterial and viral diseases.

Beyond the conventional methods, a set of modern tools now supports and accelerates crop improvement: genetic engineering, plant tissue culture, protoplast fusion (somatic hybridisation), molecular ma…

New Plant Engineering Techniques, or New Breeding Techniques (NBT), are a collection of methods that speed up and sharpen the development of new traits in plant breeding, often by editing the genome d…

Biofortification is the breeding of crops to carry higher levels of vitamins and minerals, or more and better-quality protein and healthier fats, and it is regarded as one of the most practical ways t…

Seed is one of the most crucial elements in the livelihood of agricultural communities: it is the repository of the genetic information built up in a crop species and its varieties through continuous…

Traditional seed protection relies on locally available materials rather than manufactured chemicals. Seeds have been coated with fine red soil, Guntur chilli powder, neem leaf powder, bitter gourd po…

Modern seed protection uses standardised chemical and physical treatments to improve germination and guard seed against disease, pests and poor storage conditions.

Seed storage effectively begins on the mother plant itself, from the moment the seed reaches physiological maturity, and storage in the broader sense is the preservation of viable seed from the time i…

Seeds can be grouped in more than one way according to how they behave in storage. Roberts (1973) classified seed by physiological storage behaviour into two categories: orthodox seed, which can be dr…

Seed storage methods range from simple traditional structures to highly controlled modern facilities. Conventional storage uses bamboo structures, mud or earthen structures, wooden structures and unde…

Seed certification is a legally sanctioned quality-control system for the multiplication and production of seed.

This section carries the chapter's Evaluation exercise for Plant Breeding — a set of objective (assertion-reason, fill-in-the-blank, odd-one-out, matching) and short-answer questions covering the whol…

Sample papers and previous-year board questions for this subject.