多花黑麦草×苇状羊茅杂种后代的细胞学可育性和越夏性

CYTOLOGY AND FERTILITY AND OVER-SNMMER ABILITY OF HYBRID PROGENIES BETWEEN LOLIUM MULTIFLORUM AND FESTUCA ARUNDINACEA

二倍体和四倍体多花黑麦草×苇状羊茅杂种 F_1 花粉母细胞减数分裂染色体具有较高的配对水平,单价体少,二价体多。存在低频率的三价体、四价体和较低频率的五价体,表明多花黑麦草和苇状羊茅染色体之间存在同源或部分同源和异源苏会配对,F_1 正常花粉频率平均为0～18.2%,不同杂交组合甚至同一组合不同植株均有很大的差异。F_1 的回交结实率很低,平均为0.05粒种子/小穗,且易与多花黑麦草回交。杂种后代自交结实率与其亲本一样均很低。开放授粉结实率则随着世代的增加显著提高,F_1 代平均仪为0.4%,至第五代高达65.5%。杂种后代越夏性以 F_1为最强,平均达79.9%,介于双亲之间或与苇状羊茅相近,随着世代的增加越夏性则逐渐丧失。推测越夏性丧失与杂种后代群体过早或过多地丢失苇状羊茅染色体,减少了优良基因重组的机会有关。育性正常、越夏性较强的黑麦草型第四代选系“891”的获得,表明把苇状羊茅的越夏性部分地转移到多花黑麦草中是可行的。

The chromosome number,chromosome pairing,fertility,and over-summer ability were determined among the progenies derivd from tetraploid and penta-ploid hybrids between diploid and tetraploid Lolium multiflorum and Festuca arun-dinacea.Both tetraploid and pentaploid hybrids showed a high level of meiotic chromosome association.Most chromosomes formed bivalents.The univalents,trivalents,and quadrivalents were observed frequently,and then the pentava-lents were found with very low frequencies.It was concluded that there would be both allosyndetic and autosyndeLic (or segmental autosyndetic) chromosome pairings between L.multiflorum and F.arundinacea.The normal pollen percen-tages of hybrids ranged from 0 to 18.2% and had great differences among di-fferent plants.The backcrossed seed-settings of the hybrids averaged 0.05 seeds per spikelet.The seed-setting (%) backcrossed to L.multflorum was,on the ave-rage,higher than that to F.arundinacea.There were very low selling seed-se-ttings in the hybrid progenies similar to their parents.However,When the progenies advanced,their seed-settings of open-pollination increased rapidly.se ed-setting percentages varied from 0.4% in F_1 hydbrids to 65.5% in G_4,the fourth open-pollinated generation.The F_1 hybrids had the highest over summer ability among all hybrid derivatives.The over-summer percentages of F_1hy-brids averaged 79.9%,which was intermediate between both parents or similar to tall fcscue.It was assumed that a highly low over-summer ability of the genies would be related to the too early or excessive deficiency of Festuca chpomo-somes which was adverse to select desirable zecombinants with a high over summer ability.However,the creation of the fourth generation population‘No891’ which was Lolium-like type with the high over-summer ability revealed that it conld be effective to transfer the over-summer character from tall fescue to italian ryegrass.