Comparisons of Various Alfalfa ( Medicago sativa L. ) Drought Tolerance Under Water Stress and Frequent Cutting
Magdy M . Mohamed ( 1) Z . Staszewski ( 2 ) and A . Rammah( 1)
(1) Forage Crops Research Department , Field Crops Research Institute , A.R.C., Giza , Egypt
(2) Plant Breeding and Acclimatization Institute , IHAR , Radzików , Poland .
Alfalfa ( Medicago sativa L. ) grown in arid and semiarid regions for forage , requires large amounts of water for high production under frequent cutting . So , improvement of alfalfa water-use efficiency could be effective to achieve varieties for profitable production in these zones .Although drought reduce the herbage yield of all legumes , alfalfa has the greatest yield potential in drought ( Peterson et al., 1992 ) . Therefore , eighteen of alfalfa varieties were studied in order to evaluate their water stress tolerance . Following varieties were included : five Egyptian ( Giza-1, Ismailia-1, Ismailia-94, New valley and Sewa ), eight of USA ( CUF-101, Haygraze Dual, Legend, Magna Graze, Magnum IV, Vernal , WL-605 and WL-610 )one French ( Luzelle ) and four Dutch ( Marina, Medina, Midi and Oro ). The plants were subjected to five water capacity variations ( 75 %, 60 %, 45 %, 30 % and 15 % ) harvested for ten cuts . The experiment was carried out in greenhouse ( 20 - 35 0C ) in 8 kg capacity pots which were filled with a mixture ( 3:1:1 of soil , sand and peat ) Each variety was grown in 4 pots and 4 plants per pot . Results of statistical analysis revealed significant influence of water capacity on investigated varieties and their interactions for measured characters .The varieties from arid centers such as Egyptian varieties excelled the another varieties in most traits such as plant height , shoots per plant , fresh and dry weight , leaf to stem ratio and root to shoot ratio . In general , the drought stress reduced alfalfa growth . In addition , the drought - stressed plants were shorter and had increased root to shoot ratio and decreased shoots per plant , shoot , root and total plant weights than non - stressed plants. Lemaire et al. (1989 ) reported that , the higher values of leaf to stem ratio observed during the drought at a given time were therefore entirely due to a lower aerial dry matter ( ADM ) accumulation than when water was non limiting . Genetic and phenotypic correlations among studied characters which accompanied with significant estimates of heritability and genetic variability concluded that , the selection criteria based on these characters will serve the purpose of improvement of drought tolerance in alfalfa . This result was in agreement with Wissuwa and Smith (1997) who stated that, the selection based on multiple traits may be necessary to obtain significant gains in tolerance to summer irrigation termination ( SIT ) in alfalfa .
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