BREEDING RUST RESISTANT TREES: MODERATOR'S SUMMARY 639 



We in CIMMYT are now convinced that Triticale - a man-made cereal 

 species - is on the verge of becoming a commercial crop that will compete 

 successfully with other small grains. How soon this happens will depend 

 largely upon the amount of research effort that is devoted to further 

 improving this species. CIMMYT is distributing its best lines to all 

 research organizations who are interested in working with this new crop. 



WHAT ARE THE POSSIBILITIES OF DEVELOPING OTHER MAN-MADE CROPS OR 

 TREE SPECIES? 



The rapid progress now being made in the improvement of Triticales 

 naturally stimulates one to consider the feasibility of making other wide 

 crosses, either for the improvement of parent crop plants or for the 

 creation of entirely new ones. 



Within the past decade, as has been indicated by Dr. Ernst Schreiner, 

 tremendous progress has been made in the basic sciences that bear on the 

 feasibility of such undertakings. It is now possible to grow haploid 

 plants of rice, barley, and wheat from anthers, when the proper media are 

 employed (Nichell and Torrey, 1969) . Embryo culture techniques have 

 improved greatly. Tissue culture techniques, involving the use of hor- 

 mones and many new, more efficient nutrient media, have produced spec- 

 tacular results. It is now possible to isolate apparently undamaged 

 individual protoplasts of wheat, carrot, tomato, soybeans, and other 

 species by the use of the enzymes pectinase and cellulase. In some cases 

 when cellulase has been removed from the system, the protoplasts have 

 been able to resynthesize the cell wall. Fusions also have been obtained 

 between two protoplasts within a species. 



These events definitely open the door to the possibilities of using 

 protoplasmic fusion and cell hybridization as a future tool in plant 

 breeding. It is now possible, employing proper techniques, to begin with 

 a single somatic tissue cell of many different plants, i.e., carrot, 

 tobacco, endive, parsely, rice, and sugarcane, and regenerate the entire 

 plant, including the production of seed. Hybrid seed and seedlings have 

 been obtained from wide crosses by using Giberellic acid to facilitate 

 the consummation of fertilization, followed by embryo culture. Using 

 such techniques, Kruse has reported obtaining hybrid seedlings of 

 Hordeum x Secede and more recently, tentatively, between koena x Tritieum 

 (personal communication). To date, however, there has been no report of 

 his having formed the amphidiploid of these hybrids . 



Although I am fascinated by the eventual feasibility of using cell 

 hybridization for plant improvement, I nevertheless feel that there are 

 other avenues that are more immediately feasible. In light of our recent 

 success in progress with Triticale improvement, and Dr. A. Kruse 's 

 preliminary report on successful hybridization of barley x rye, and oats 

 x wheat, and the reported but unproven occurrences of natural hybrid 

 seedlings of maize and sorghum, it now appears the time has come to launch 

 an aggressive program in crop plant improvement based on wide crosses. I 

 propose that such a program be undertaken to improve both cereals and 

 legumes. It should include attempting to make as many crosses between 

 different genera of cereals as possible, employing all of the most modern 

 techniques to consummate fertilization, to cultivate the embryoes , and 

 to form the amphidiploids . If a series of amphidiploids of diverse 

 genetic backgrounds can be produced, this will open the door to vast 

 further improvement through conventional breeding approaches. I feel 



