RA 00048.pdf - OAR@ICRISAT

The Starch for Apospory in Sorghum L
V. Seshavatharam and U. R. Murty
Abstract
The possibility of producing perpetual hybrids in sorghum has prompted an investigation of the embryology of
Sorghum halepense. Sorghum halepense was on record as having some apomictic tendencies as revealed through its
breeding behavior. The mechanism underlying such a behavior could be due to the occurrence of apomixis in the
aposporous embryo sacs, as the embryological study of this species reveals the existence of somatic apospory in
some ovules that are potentially capable of developing into an aposporous embryo sac. The aposporous initials could
be discerned in slightly older ovules, only after the differentiation of the megaspore mother cell or its further
development.
Chromosomal Structural Hybridity and Breeding Systems
in Sorghum blcolor (L.) Moench
P. B. Kirti, U. R. Murty, and N. G. P. Rao
Abstract
The study was undertaken to find out whether sexuality, cross-sterility and apomixis have any chromosomal basis. A
facultatively apomictic line (R-473), a cross-sterile line (101), four normal lines (White Seed, Kafir-B. IS-84 and Aispuri)
and four F 1 hybrids were examined at the mid-prophase stage of meiosis. Unpaired chromosomal regions were
noticed at the pachytene stage in the apomictic and cross-sterile lines but not in the normal sexual lines. F 1 hybrids
between normal sexual lines (Kafir-B x Aispuri) did not exhibit any abnormalities in chromosome pairing but those
between sexual and apomictic lines were structurally heterozygous. Chromosomal structural differences can,
therefore, result occasionally in abnormal breeding systems including apomixis. This study indicates that crosses
between divergent materials may help achieve obligate apomixis.
Developmental Studies in Cytoplasmic Genetic Male-sterile Sorghum Lines
L. L. Narayana, R. N. Reddy, N. G. P. Rao. and K. D. Pillal
Abstract
The develoyment of anther, male gametophyte, ovule, and female gametophyte in the male-sterile sorghum lines,
G-1A, CK-60-A, VZM-2-A and M-35-1 has been studied. Abnormalities such as intratapetal syncytia, thickening of
tapetal cell walls, abnormal radical elongation of tapetal cells, early disorganization of tapetum and cytomixis are
responsible for male sterility in these lines. The embryo sac develops according to the polygonum type and is thus
sexual. Because of pollen sterility, fertilization fails to take place under selfing. In the absence of fertilization, sexual
embryo sacs degenerate and consequently there is no seed set. However, in G1A and CK-60-A a tendency for the
formation of aposporous embryo sacs and degeneration of the megaspore mother cell on the products of meiosis has
been noticed. By continued selfing it may be possible to induce apomixis in these lines.
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