Glossary Plant Breeding

horizontal resistance. Owing to race non-specificity, the resistance is only partial,
albeit durable and stable.
Hormone. A molecule that is secreted by an endocrine organ into the circulatory system
and that acts as a long-range signalling molecule through activating receptors on or
within target cells.
Host. A cell or organism whose metabolism is used for the growth and reproduction of a
virus, bacteria, pathogen, or any other parasite.
Host Evasion. A mechanism of functional resistance in which phenologies of the host
and insect do not synchronize. It takes place when plant growth pattern is modified so
as to bring in asynchrony of insect-host phenologies. For example, early planting of
rice saves the crop from gall-midge attack.
Host Range. The spectrum of strains of a given plant species that a given strain of pest
can infect.
Hot Spot. A place where an endemic disease(s) or pest(s) occurs regularly during
cropping season. In genetics, it is a part of a gene that shows a very high tendency to
become a mutant site, either spontaneously or under the action of a particular
mutagen.
Hybrid Breakdown. DistortedsegregationintheF 1 hybrid leading to the recovery of
parental types (cultivated and wild relatives) in the F 2 or later segregating or
backcross generations. It may be ascribed to centromeric affinity, cryptic structural
hybridity, gene substitution or unfavourable nuclear-cytoplasmic interactions. In
certain interspecific hybrids of rice, hybrid breakdown has been reported due to
duplicate recessive genes in the F 2 and later segregating generations.
Hybrid Corn Makers. An acronym used in recognition of pioneer works of early maize
breeders like Shull, East, Jones, Hays, Rickey and Jenkins.
Hybrid Cotton. The cross product of genetically different parents of cotton. The term is
also used to designate transgenic cotton, the lint of which would have the properties
of original cotton as well as polyester. Clothes made from such cotton would behave
like present cotton-clothes besides zero shrinkage. This way farmers may put
challenge to polyester industry.
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