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Spontaneous Multi‐Pistil Mutant mp1 in Alfalfa: Floral Anatomy and Embryo Sac Development
Author(s) -
Jin Liang,
Zhang Jingwen,
Li Jing,
Yang Yang,
Zhang Xiaoqiang,
Wang Xiaojuan
Publication year - 2014
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2013.0406
Subject(s) - gynoecium , ovule , biology , stamen , pollen , egg cell , botany , pollen tube , megaspore , population , pollination , demography , sociology , sperm
A spontaneous mutant with two to three pistils, mp1, was identified from ovule fertility investigations in a natural alfalfa ( Medicago sativa L.) population. No cytological investigations of pistil development and seeding mechanisms in reduced‐fertility multi‐pistil mutants have been performed to date. In this study, floral ontogeny, embryonic development, and pollen tube guidance were compared between alfalfa mp1 and wild‐type flowers. The results indicated that pod‐setting of mp1 was significantly lower (8.18%) than that of wild‐type plants (71.43%), which indicates that mp1 was partial‐female‐sterile. In the late stage of floral development that forms stamen and pistil organs, an extra carpel was visible in mp1 in place of the vexillary stamen. Normal patterns of megasporogenesis forming a functional chalazal megaspore were observed both in mp1 and wild‐type plants. However, mp1 showed abnormal development during megagametogenesis for more than one egg cell and two synergids in mature embryo sacs. In comparison with a fertile flower, the stigma of mp1 has no honeycomb‐like cuticle and less exudate to adhere to pollen grains. Furthermore, pollen tubes of mp1 grew in a disordered fashion and could not penetrate into ovules through micropyles, while pollen tubes from fertile plants were attracted to the micropyle in the “N” way and grew in a highly organized manner. This study is the first report of a spontaneous multi‐pistil mutation in M. sativa . Our results reveal that mp1 is a new floral homeotic mutant with partial female sterility due to abnormal female gametogenesis, stigma development, and pollen tube guidance.