Smith - 2003 - Rice origin, history, technology, and production

Origin, Domestication, and Diversîficatîon
EVOLUTIONARY PATHWAY OF 0. SATIVA CULTIVARS
Proposed Evolutionary Pathway
The unified postulate on the Gondwanaic origin o f the genus and the parallel evolution
o f the two cultigens amplified and strengthened an analytical approach to
the im portant question: How did O. sativa cultivars evolve? Controversies lingering
from the days o f Watt (1891) and de Candolle (1886) in the late nineteenth century
were concerned largely with the choice between a perennial parent such as O. rufipogon
and an annual form, then called O. sativa f. fatua or f. spontanea (cf. Chang,
1964b). O n top o f the confusion, the ambiguous taxon “O. perennis M oench” o f
diverse geographic origins and uncertain description was used repeatedly by Oka and
co-workers, and others as the ancestral species. “O. perennis M oench” was named
early in 1794 and used by Chatterjee (1948), Sampath (1962), and others in varying
instances. Following Tateoka’s visit to several botanical museums in Europe and the
United States, the specimen was found missing, and various descriptions by later
workers differed widely (Tateoka, 1963,1964). Thus “O. perennis” lacks the requisites
o f a valid botanical species (see Chapter 1.2). Moreover, the distinction between a
perennial or annual growth habit is not so pronounced in diverse environments o f
the tropics as to be a valid classification criterion (Tateoka, 1964; Chang, 1976d).
Tateolca (1964) suggested the use o f O. rufipogon Griff, to designate Asiatic, African,
and American forms in his “ O. sativa complex.”
Then Sharma and Shastry (1965) described and proposed the name O. nivara
Sharma et Shastry for the Asian annual wild form o f the O. sativa complex in northern
India. A m ore restricted description was given o f O. rufipogon. This development
facilitated a delineation between the more primitive perennial forms and the annual,
more advanced wild rices, although samples o f O. nivara provided to me by Sharma
did not agree with his description in many respects (my personal observation). Yet
m ost samples taken from the field were judged as weed races (according to Harlan
and de Wet, 1971) which came from natural hybridization between two wild species
or among three species: rufipogon^ nivara, and sativa and their hybrid progenies. Thus
elegant statistical treatm ent of random samples talcen from the field without prior
knowledge of their phylogenetic origin and site history may not reveal or lead to a
true picture o f the complex events of past centuries. The evolutionary pathway o f
O. sativa and wild relatives is shown in Figure 1.1.2.
Perennial versus Annual Ancestor
The line o f descent in O. sativa is probably from a wild perennial to a wild annual and
onto an annual cultigen. Also involved ai*e weedy forms, which could have played a
role in the long process o f evolution (Chang, 1976a,b). Chang also emphasized that
the status o f the putative progenitors should be regarded as conceptual species o f the
past as true-to-type specimens likely are not to be found in the disturbed habitats
o f today. This scheme, based on past findings of many workers and observations
o f the author, has been accepted generally by rice workers and otlrers. The choice
o f an annual wild form, propagated mainly by seed, as the immediate progenitor