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Male sterility is the failure of the male gametes to be produced
viable i.e there is no formation of the viable pollen grains which
carry the male gametes in plants. The pollen grain is
non-functional but the female gametes function normally. It occurs
in nature sporadically, perhaps due to mutation. Male sterility is
also due to environmental factors. Male sterility in crop plants is
classified in the following types (1) Genetic Male Sterility (GMS)
(2) Cytoplasmic Male Sterility (CGMS). (3) Temperature-Sensitive
Genetic Male Sterility (TGMS). (4) Chemically-Induced Male
Sterility (CIMS). (5) Photoperiod-Sensitive Genetic Male Sterility
(PGMS). (6) Transgenic Genetic Male Seterility (Tr.GMS). Wheat
improvement by genetic engineering requires the delivery,
integration and expression of defined foreign genes into suitable
regenerable explants. Initial attempts at introducing transgenes
into wheat employed protoplasts as explants due to the absence of
cell walls. Initial steps for genetic transformation involves
delivery of a gene cassette into recipient cells followed by
analysis of the expression of delivered gene.
Bread wheat (Triticum aestivum L.) is a major food crop in the
world and a staple food of Pakistan which plays a remarkable role
in meeting the food requirements of the country.Worldwide wheat
provides nearly 55% of the carbohydrates and 20 % of the food
calories consumed globally. Most of the wheat is growing for human
consumption and about 10 % is retained for seed and industry. On
the world basis it ranks after rice providing chief protein and
caloric requirements for one third of the world population and is
consumed in a variety of ways.At present though the production of
wheat is increasing gradually but yield is still trailing the
average obtained in similar ecologies elsewhere. A significant
yield improvement is still possible through the development of high
yielding varieties that are adaptable to various agro-climatic
conditions. Manipulation of accessions for exploring genotypes with
best combining ability and identification of transgrassive
segregates by using modern genetic tools is prerequisite for high
yielding varieties. Current studies on combining ability and
authentication of F1 hybrids provided excellent results in this
regard.
Chickpea is the principal rabi pulse crop and important source of
calories which is predominantly grown in the vast rainfed areas of
Pakistan. Pakistan ranks second to India in terms of acreage
Pulses, dry edible seeds of leguminous plants, constitute an
important source of balanced human diet throughout the world. Among
the pulses, chickpea is the third leading grain legume in the world
and first in the South Asia. Ninety two percent of the area and
eighty nine percent of the production of grain are concentrated in
semi-arid tropical countries of the world The present study
pertaining to the estimation of genetic parameters and trait
association in eighty chickpea genotypes was conducted in the
glasshouse of the Department of Plant Breeding and Genetics,
University of Agriculture, Faisalabad. Correlation studies for
different seedling parameters were found to be associated with each
other positively and significantly. On the basis of these results,
it may be concluded that seedling length, root length, seedling
biomass, leaf length, leaf width and leaf area significantly
related with the seedling health. We can select genotypes at
seedling level for improvement.
A limiting factor in wheat production in many countries is the
occurrence of temperature stress at grain filling stage especially
in West Asia and North Africa. In about 40% temperate environments
constituting 36 million hectares, terminal heat stress is a major
threat. Keeping in view this threat present investigations were
made to explore sources of heat tolerance and its genetics.100
genotypes of wheat were screened in a plastic tunnel for heat
tolerance by providing them heat stress at the time of anthesis.
Selection of the genotypes was based on grain weight, number of
grains per spike and grain yield per 25 spikes after computation of
their relative ratios. The selected genotypes were also tested by
measuring their electrolyte leakage to confirm the tolerance and
susceptibility by calculating relative injuries. Seven genotypes
including 3 heat tolerant, 1 moderately tolerant and 3 susceptible
were crossed in a 7 x 7 diallel fashion.The information obtained
from these results during the current studies may be used to evolve
high yielding varieties which can produce higher yield and help
maintain yield sustainability in those areas where terminal heat
stress is a major threat.
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