Glossary Plant Breeding

when either the host or the pathogen, or both produce wrong products or nothing at
all.
Proteome. The complete set of protein-coding genes in a genome.
Proteomics. The cloning and molecular characterization of the complete set of proteincoding
genes in a genome.
Protogyny. Just reverse of protandry. It is a mechanism in which stigma becomes
receptive first, (i.e., before pollen shed; for example, pearl millet, walnuts, etc).
Notice that both protandry and protogyny are analogous in that both fosters crosspollination.
Proto-oncogene. The normal cellular counterpart of genes that can be mutated to become
dominant oncogenes.
Protoplasm. The cytoplasm and nucleoplasm of the cell.
Protoplast. A plant cell devoid of the wall. The wall of the cell is digested by an enzyme,
called cellulase (and macerozyme). Enzymatic treatments yield a large quantity of
protoplasts without cell breakage and osmotic shrinkage. Viability of the protoplasts
can be tested by the presence of photosynthetic and respiratory activity; however,
fluoroscein diacetate is frequently used to test the viability. Cultured protoplasts can
be used not only for somatic cell fusion but also for taking up foreign DNA.
Protoplast Fusion. Also called somatic hybridisation; the fusion of protoplasts from two
diverse sources aided by suitable fusogenic treatments. It is one of the important uses
of protoplast culture. A variety of fusogenic treatments are available, which include
NaNO 3 , high pH with Ca ++ , polyethylene glycol and electrical impulse. Such agents
bring the protoplasts together, cause them to adhere with one another for bringing
fusion. It is used to hybridise otherwise sexually incompatible (cross incompatible).
Somatic hybridisation has been used in Nicotiana, Datura, Petunia, Solanum, and the
like.
Prototroph. A strain of organisms that will proliferate on minimal medium (without any
supplemented nutrient such as an amino acid, a vitamin or a hormone).
Provirus. A virus “chromosome” integrated into the DNA of the host cell.
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