الفهرس 
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Abstract
Alfalfa ”Medicago sativa, L.” that has large genetic diversity, is among the most important forage crops ”king of forages”. That provided alfalfa genotypes to occupy different environments. The importance of alfalfa forage goes to its high content of protein and minerals, beside, high degree of palatability. Voulianteer weeds in alfalfa fields are mostly of lower quality and palatability, especially ”Urospermum picriods” and ”Xanthium spinosus”. That affect the value and persistence of alfalfa fields.In Egypt, the total area cultivated to alfalfa was about 79 thousand faddan (one fad= 4200 m
2 ). The great shortage in animal protein force the expansion of forage cultivation. Alfalfa represts a suitable choice, since, the available land and water are of lower quality.
Selective herbicides as a control measure in alfalfa fields were used very little.That goes to its
high price, limited effectiveness and herbicidal injury. Glyphosate is a systemic non-selective
foliarly applied herbicide. Irrespective of glyphosate non- selectivity, several plant species
exhibit levels of tolerance to its effect, reductions to sorption and limited translocation from
vegetative to reproductive organs. Several trials has been made to select a glyphosate
tolerance genotypes in vitro. In each of them tolerance was due to an increase in 5-enolpyruvy
shikimate 3-phosphate synthase ( E P S PS) activity. The recent study was an attempt to trace
variability in glyphosate tolerance of alfalfa germplasm. The improvement in tolerance due torecurrent selection was also considered. <Alfalfa plant materials (Medicago sativa,L. ) used in that recent study will be referred to as the five base populations .Two cycles of recurrent selection for Glyphosate tolerance
were imposed on each base population. Cycle one was practiced on 2800 plants per each base
population (C0). Four weeks after seeding, plants (8-15 cm tall) were treated with 0.56 kg acid equivalent per hectar (ae.ha
-1< of Glyphosate (Round up®) diluted in 480 liter of water (L). Survived plants were left to complete the first cutting growth (two months). Regrowth of the
second cutting at 20-25 cm height was sprayed by 0.84 kg ae.ha-1 glyphosate in 480 L water. ha-1
. 14 day after treatment, plants was rated for injury on a 1 to 4 scale (where 1= uninjured, 2=injured shoot, 3=dead shoot with live auxiliary shoots and 4= dead seeding) (Boerboom
et.al,1991). The uninjured plants were selected uprooted and transplanted to an isolated plots
surrounded and covered by insectproof cloth for flowering and seed setting .Plants selected
for Glyphosate tolerance from each germplasm were 100 plant . Seeds were harvested for
each separate plant as a half-sib family. Equale seed weight from each selected half-sib
family seeds were bulked to from first improved cycle (C1). The second cycle of selection was
practiced for each separate improved population. Each population was seeded in 20 rows of
1.25m. long and 0.80 m apart (2000 plant). Four week old seedlings were treated with
Glyphosate at 0.56 kg ae. ha-1
in 480 liters of water. Fourteen days after treatment, injury
levels were rated. The uninjured plants were selected uprooted and transplanted to an isolated
plots surrounded and covered by insect proof cloth for flowering and seed setting .Plants
selected for Glyphosate tolerance from each germplasm were 100 plant . Each germplasm
was caged separately in cloth house and a portable honey bees heave (Apis mellifera L.) was
used as pollinators. Seeds were harvested for each separate plant as a half-sib family. Equale
seed weight from each selected half-sib family seeds were bulked to from second improved
cycle (C2).