HORT exam 2 Flashcards
Centers of Diversity and Origin
it’s where different facilities have opened up where the crop has originated to keep a germplasm research available and to continue trying to diversify the plant. 8 total
Nikolai Ivanovich Vavilov devised them.
Two incompatibility types
1.self-incompatibility: pollen cannot fertilize its own pistil – Gametophyte or Sporophyte
2.cross-incompatibility: pollen of one plant cannot bring about fertilization in other genotypes of the same species
Two incompatibility systems
1.Heteromorphic flower structure
2.homomorphic floral structures:
homophorphic flower structures
no morphological differences (the stamens and styles attain comparable lengths); flowering structures are similar in both the pollen-bearing and seed bearing-plants
Heteromorphic flower structure
incompatibility results from the presence of a sporophytic incompatibility system which is associated with morphological differences in pollen- and seed-bearing structures in bisexual flowers, e.g. the relative lengths of the stamens and style.
3 male sterility forms
- The pollen is absent or extremely scarce, termed pollen sterility.
- Severe malformation or absence of the stamens or male flowers, called staminal sterility.
- The pollen is completely normal, but the anthers fail to dehisce, called positional or structural sterility.
3 male sterility types
Genetic male sterility
cytoplasmic male sterility
genetic-cytoplasmic male sterility
genetic male sterility
sterility depends on a single (usually recessive) gene usually represented by ms. More complex systems have been reported. Propagation of genetically male sterile plants and hybrid production using male sterility requires special procedures.
cytoplasmic male sterility
this type of sterility is under the control of cytoplasmic factors as opposed to nuclear factors. Plants with certain types of cytoplasm are male sterile, but will produce seed if special pollinators are present.
genetic cytoplasmic male sterility
sterility depends upon the interaction of one or more genes with a particular cytoplasm, with neither one alone being sufficient to cause male sterility. This type of male sterility differs from cytoplasmic male sterility alone in that the offspring of male sterile plants are not necessarily male sterile, but may be fertile when certain fertility-restoring genotypes are used as pollinators. These male parents carry genes (in nucleus) which have the ability to restore the pollen-producing ability of plants with cytoplasmic male sterile type cytoplasm. Therefore, in this case, sterility depends upon the interaction of nuclear and cytoplasmic factors.
different types of mutation
Recessive vs dominant mutations
The second source of genetic variability is GENE FLOW
the spread or migration of new genes from one interbreeding population to another owing to the dispersal of gametes or zygotes. In plants, we especially think of pollen dispersal and seed dispersal
mutation breeding
INCREASE THE GENETIC VARIABILITY
use of mutagenic agents as approach to plant breeding, radiation, chemical mutagens, plant materials, seeds
Genetic drift
since with each sample certain genes within gametes are eliminated indiscriminately, genetic drift tends to ERODE VARIATION.
self-pollinated
the homozygous nature of the individual plant is exploited.
leads to segregation and homozygosity
1. A single homozygous genotype (from pure line selection) or
2. a mixture of homozygous genotypes
