Studies On Crossing Improvement Of Male Sterile Lines Ms-4 Of Alfalfa

The male sterile line of alfalfa is important material for heterosis .The male sterile line Ms-4 of alfalfa was selected from Medicago varia Martin.cv.'Caoyuan No.1'by professor Wuyongfu in 1978.It can not be widely used in production because it's pistil has lower fertility .So selecting the new better male sterile lines of alfalfa rapidly and effectively is the urgent problem to be solved.The good male sterile lines of crop were selected by backcross .So backcrossing is an effective method for improving male sterile line. It need select the early generations from backcross offspring for improving breeding efficiency. In this study, two methods of backcross were used. One is male sterile line in crossing with male parents that have better characters, then select fertile plants from F1,using it in backcrossing with male sterile line. The other is male sterile line in crossing with male parents that have better characters, then select sterile plants from F1, using it in backcrossing with male parents .The sterility of male sterile lines and pistil fertility of early generations from backcross offspring were analysed by tissue culture, cell morphology, isoenzyme and molecular marker .The results showed:1 There are 24 male sterile lines were selected with pollen staining reaction and bioassay by the method that using male sterile line in crossing with male parents that have better characters, then select fertile plants from F1,using it in backcrossing sterile line.2 Tissue culture is an effective method for propagation of male sterile line of alfalfa before maintainer line was found. Blad stems are good explants of inducing callus. Callus inducing rate is 85.6%.The medium that add Proline and Ammonium Sulfate is benefit for somatic embryos inducing. The rate of somatic embryos inducing is 90%. The productivity of somatic embryos is high.3 The results of agronomic character and cell morphology of stigma and style of 24 sterile plants selected from early generations showed: the setting percentage of BC1A1-21 and BC1A1-22 is improved significantly; the stigma enlarge significantly ,the area of mastoid cells exterior is large; hairy cells are longer and abduction.Style is larger and wide; there are 6-8 layers cells between epidermal and passage cells ; The arrangement of passage cells was tight .The fertility of BC1A1-22 and BC1A1-21 is improved significantly.4 The POD and EST isoenzyme of parents and cross generations in different grow periods and organs were analysed by using polyacrylamide gelelectrophoresis. The results showed: the isoenzyme pattern of F1 are complementary type of parents or have distinguished bands.The isoenzyme pattern of BC1 is lean to recurrent parent.5 The genome DNA of parents and cross generations were analysed by RAPD. The results showed: MSS126438 is the molecular marker that link to male fertility of alfalfa. BC1A1-1,3,6,9,21,22,27,BC1MC1-4,6,7,11,13,14,15 are confirmed male sterile plants by MSS126438. The result is approximatly consistant in above methods. It is further identifying method for male fertility.