An adventure in applied science - IRRI books - International Rice ...

104 History of the International Rice Research Institutesions at a time, there was a backlog in the first few years. Later, however, thenumber of annual additions decreased and the scientists were able to keep upwith the incoming accessions.By 1963, the world collection had increased to 9,430 varieties and 1,194mutants, testers, and other species of the genus Oryza. From then on, it grewmore slowly, numbering 9,779 in 1964, 9,913 in 1965, and 10,323 in 1966.Compared with IRRI’s current collection of nearly 55,000 varieties and geneticlines, the collection in 1966 seems rather small. Nevertheless, even at that time,the Institute had by far the worlds largest single rice collection.Besides providing the basis for IRRI’s rice breeding program, the ricescollected were available, on request, to rice breeders everywhere. Requestsbegan coming in as early as late 1962, and IRRI sent out 400 seed lots to 14countries that year. In 1963, the number of samples shipped — to 26 institutionsin 17 countries — jumped to 2,296. In 1965, IRRI sent 1,608 varieties to 56institutions in 26 countries, and in 1966 the figure was 1,052 varieties to 41countries. By then (as reported later in the section on the rice breedingprogram) the Institute was able to distribute varieties it had tested thoroughlyas well as progeny from its own crosses that showed great promise. Jenningstook charge of the world collection the first several years, and after he left forColombia in 1967, Chang assumed full responsibility for the project.Basic research projectsBoth Jennings and Chang devoted considerable effort to basic studies of rice.None of this was pure research or research for its own sake but rather a searchfor the answers to questions that arose as they attempted to breed superiorvarieties of rice. The studies were so numerous that only a few of the moreimportant can be reported here.An early project of Chang’s was to study the genetics of the inheritance ofplant height. Crossing the tall Peta variety with the short-statured variety Deegeo-woo-gen,he found that in the F 2 generation, three-fourths of the plantswere tall and one-fourth were short, thus fitting the Mendelian ratio of 3:1. Hisstudies proved that tallness was dominant over shortness and that shortstature was controlled by a single recessive gene. If the inheritance of shortstature had been complex, IRRI never could have made such fast progress inits rice breeding program. It is interesting that although Taichung Native 1 wasdeveloped in Taiwan in the mid-l950s, the simple inheritance of its shortnesswas not known until Chang discovered it at IRRI in 1963-64.One of the first studies made by Jennings sought a quick and efficientprocedure for crossing rice varieties. The technique he devised in 1962-63 wasto emasculate the florets by cutting the glumes with scissors just below theanthers. This was done in the afternoon before the morning when the plantswould be pollinated. Any anthers left after clipping were picked out withforceps. The next morning, panicles of the male parent were shaken over theclipped anthers, and the panicles of the female parent were bagged. Thismethod of making crosses is still used by IRRI plant breeders.