BREEDING RUST RESISTANT TREES: MODERATOR'S SUMMARY 533 



The impact of the high-yielding, fertilizer responsive, light- 

 insensitive, dwarf Mexican varieties on yield and production of wheat in 

 Mexico, Pakistan and India is shown graphically in Figures 1, 2, 3, and 4 

 The Mexican varieties have made Pakistan self-sufficient in wheat produc- 

 tion and have helped India take a giant step in this direction. It is 

 estimated that they have increased the combined gross national product 

 (GNP) of the two countries by 1.5 billion dollars during the past two 

 harvests, compared to the 1965 base which was a previous all-time record 

 crop (Borlaug, et at. , 1969) 



Amazingly although the Mexican dwarfs were bred and developed for 

 irrigated areas, they also are proving to be highly effective under rain- 

 fed areas in many parts. Approximately 20% of the barani (rainfed) area 

 sown to wheat in Pakistan is in Mexican dwarfs. Virtually all of the 

 Afghanistan area sown to Mexican dwarfs and more than 80% of the Turkish 

 area is rainfed. Next year about 20% of the entire area sown to wheat 

 in Tunisia, virtually all of it rainfed, will be in Mexican dwarfs. 



During the 1968-69 crop season, Mexican wheat varieties were grown 

 on more than 20 million acres in foreign countries. This is more than 

 10 times the entire area sown to wheat in Mexico, the country for which 

 they were bred. Little did I realize 3 when we initiated the breeding 

 'program 25 years ago to assist Mexico to become self-sufficient in wheat 

 production 3 that it would subsequently have a "world-wide" impact. Your 

 forest tree breeding projects too will evolve into programs with world- 

 wide impacts if you concentrate your efforts on valuable forest species, 

 develop and maintain very diversified gene pools, and develop an inter- 

 national system of cccverative testing. 



THE MONSTER GROWS 



The seriousness and magnitude of the world food problem must not 

 be underestimated. The recent, much -publicized successes of the green 

 revolution in increasing wheat, rice, and maize production in Asian 

 countires only offers the possibilities of buying 20 to 30 years of 

 time in which to bring population growth into balance with food produc- 

 tion. 



Plant breeders who look ahead must not be satisfied with maintaining 

 the current yield plateau for our major food crop plants. Complacency 

 can bring disaster. 



The unrelentless pressure of exploding world population, with no 

 relief in sight, should urge all of us tc struggle to increase the 

 potential yield levels of all food crops if we are to help ward off 

 widespread world famine within the next 50 years. 



I believe there is entirely too much conservatism in virtually all 

 plant breeding programs. One of the first lessons which we learn in 

 genetics is that maximum levels of heterosis and yield are generally 

 obtained from crossing genetically distinct parents. This principle we 

 promptly ignore in our breeding programs, with few exceptions. Most 

 programs involve crossing closely related varieties or parents. Fre- 

 quently this error is compounded by long backcrossing to the commercial 

 parent. There is very little possibility of significantly increasing 

 the grain yield potential in new varieties developed with these types 

 of approach. 



