Introduction of Pests and diseases

Pests and diseases

Introduction of Pests and diseases

· Potato tuber moths from Italy, apple woolly aphids, and citrus fluted scales from Australia.

· Coffee rust and Bunchy top of banana – Sri Lanka

· Acclimatization is the process of a variety adapting to a new habitat.

· All dwarf wheat cultivars are descended from “Mexican dwarf wheat” hybrids.

· “Genetic erosion” refers to the progressive loss of variety in domesticated forms and their wild cousins.

· Gene sanctuaries – An region of variety that is preserved from human influence.

· Trips with the goal of collecting various types of agricultural plants and their associated species are referred to as “exploration.”

· The fundamental steps of any breeding programme, are
1. Creation of variation
2. Selection.

· The following are the two essential prerequisites for selection to work:
1. Variation must be present in the population.
2. The variation must be heritable.

· “Heritability” is defined as the ratio of genetic variance to total variation (phenotypic variance).

· The difference between the mean of the progeny and the mean of the population from which selection is made is known as “genetic progress.”

· The “Progeny test” is a method of determining the value of plants based on the performance of their progenies.

· A pure line is the offspring of a single homozygous self-pollinated plant.

· Homozygocity % = (2m-1)n/2m
m = No. of generations of selfing.
n = no. of genes segregating.

· Hybridization is the process of mating (or crossing) two genetically different plants.

· The pedigree is an account of an individual’s ancestors, and it often goes back to some distant forebears.

· Isogenic lines — Lines that are genetically identical save for one gene.

· The back cross is the sole way to transmit genes between species.

· Heterosis is the superiority of an F1 hybrid over both of its parents.

· Maize has been examined for its ability to combat heterosis and inbreeding depression.

· Heterobeltosis is a condition in which the F1 outperforms the better parent.
Heterosis = [F1 – ((P1 + P2)/2)]

· Inbreeding is defined by mating between closely related individuals (or) self fertilisation. Inbreeding depression is the loss of vigour and fecundity caused by inbreeding.

· Top cross: A cross between an inbred and an open pollinated variety is known as a top cross.

· Lack of inbreeding depression characterises homozygous equilibrium.

· Test cross: When the top cross is made to assess the combining ability of an inbred the cross is called as “test cross”.

· Poly cross: Progeny of a line produced through random pollination by a number of selected lines.

· Varietal cross (or) population cross: A cross between two open pollinated varieties.

· If ‘n’ lines are to be tested in all possible single cross combinations there would be n (n-1) / 2 single crosses without reciprocals and if reciprocals are also included it would be n (n-1).

· The concept of combining ability was proposed by Sprague and Tatum.

· Combining ability refers to an inbred’s capacity to pass on favourable traits to its hybrid progenies when crossed with another inbred line.

· “General combining ability” refers to an inbred’s average performance in a series of hybrid combinations. The “top cross test” is used to achieve this.

· Specific combining ability (SCA) is a divergence from projected performance based on GCA as determined by “Diallel crossing.”

· SCA is the primary cause of heterosis.

· n(n-1)(n-2)(n-3)/8 is the number of double cross combinations.

· In cross-pollinated crops, synthetics are crucial.

· A “Synthetic” is an improved generation of open pollinated seed combination that includes a number of inbred strains.

· Synthetics exclusively use GCA, whereas hybrids use both GCA and SCA.

· Syn2 = Syn1 – (Syn1 – Syn0)/n.
n = no. of parental lines.

· A “Composite” variety is created by combining seeds from multiple phenotypically superior lines and allowing them to open pollinate in any combination conceivable.

· Germplasm complexes are created by combining seed from numerous genetically different lines (or populations).

· Recurrent selection is a method of genetic recombination that involves “reselection” generation after generation with interbreeding of selects.

· “Open pollinated variety” is a popular choice for GCA testers (broad genetic base).

· An “inbred” is used in the recurring selection of SCA testers. (a little genetic foundation)

· Recurrent selection for GCA and reciprocal recurrent selection for SCA are equivalent when dominance is full, although both are superior to R.S for SCA.

· If dominance is complete three methods are equal. If over dominance is present, Reciprocal recurrent selection and recurrent selection and recurrent selection and recurrent selection for SCA both equally superior to recurrent selection and recurrent selection for GCA.

· Male sterility is characterised by the production of non-functional pollen grains.

· By crossing the male sterile line to a heterozygous man fertile, the male sterile line can be maintained.

· A single recessive gene controls male sterility genetically.

· Srr male sterile X Frr male fertile—> Srr male sterile

· Maintainer line is fertile recessively – Frr.

· Heteromorphic incompatibility – florel must be accompanied. Differences in morphology.

· Homomorphic: no floral morphological distinctions are present.


· Pin type flowers with long styles and short stamens.
Thrum type flowers have short styles and lengthy stamens.

· The genetic makeup of the pollen determines the incompatable response in gametophytic incomparability.

· Fully incompatable – S1S2 X S1S2
Partial compatable – S1S2 X S2S3.
Fully compatable – S1S2 X S3S4.

· In Cross Pollinated crops, homozygosity increases by 50% with each generation of selfing, whereas heterozygocity decreases by 50%.

· “Shull” invented the term “heterosis.”

· Nulliplex refers to an auto tetraploid that has all recessive alleles.

· A “clone” is a collection of plants derived from a single plant through asexual reproduction.

· Cross pollination is unavoidable in sexually propagated crops.

· Pathogenicity is a pathogen’s ability to infect a host strain.

· Virulence – A pathogen’s ability to cause illness.

· The term “Immune reaction” refers to when the host does not exhibit illness symptoms.

· Phytoalexins are generated by the host in response to pathogen infection.
Fungicidal (or) fungistatic phytoalexins are two types of phytoalexins.

· Vertical resistance (resistance to only one race) is synonymous with oligogenic resistance.

· The Vertifolia effect: the emergence of an epidemic in the “Ono” cultivar, which carries vertical resistance genes.

· The reproduction rate in horizontal resistance is not zero, but it is less than one.

· For horizontal resistance, the pedigree technique is ideal.

· Sparrow is a rust-resistant wheat type that comes in three colours (yellow, black, and brown).

· Oligophagy — the ability to subsist solely on one taxonomic unit. Hesisan fly, for example (flessian fly).

· Seasonal oligophagy – Insects can live on a variety of species throughout the year. In one portion of the year, and on a few occasions in another. Aphids, for example.

· Antibiosis is the term for the plant’s detrimental influence on the insect’s biology.

· First induced mutation variety – Charina – F (tobacco).

· Mutations that have been induced Pleiotropy is most typically caused by mutations in closely related genes.

· Gamma rays are caused by gene mutations.

· Alpha rays are chromosomal abnormalities, Beta rays are chromosomal and gene mutations, and X rays are chromosomal and gene mutations.

· The use of non-ionizing agents is limited to ‘pollen grains.’

· In comparison to diploids, polyploids have a lower dry matter content.

· Allopolyploids are mostly “Apomictic.”

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