A Review of a Half Century Hybrid Maize Breeding Experiences with Combined Tolerance to Major Biotic and Abiotic Stresses in China and Other Developing Countries

Abstract

Genetic vulnerabilities (GV) of maize (Zeamays L.) have been experienced for a half century globally. Research on quantitative gene resistance (here called “co-survival tolerance”) against GV have been studied on Puccinia sorghi common rust, Exserohilum turicum northern corn leaf blight, Bipolaris maydis Southern corn leaf blight, maize streak virus, parasitic witchweed Striga species, Puccinia polysora tropical rust, Peronosclerspora sorghi downy mildew and Ustilago maydis smut. Among the above GE experiences, the most striking experience was parasitic witchweed Striga hermonthica, S. asiatica and S. aspera species in Africa. Without co-survival tolerance, Striga problems in Africa may not be solved in next few decades. The tolerance is controlled by quantitative gene. African origin parasite problems are causing damage of Africa’s food crops in 7 billion US dollars annually. Parasites and hosts must be live together and co-survive in nature. The author’s experiences of GV with maize in China have been two popular hybrids; Jeungdan 958 and Seunok 335. The former hybrid was covered over 10 million ha during the period of 2007-2013. Its genetic vulnerability due to too wide areas of cultivation of a single hybrid was occurred by corn borers and smut. While Seunok 335 and its sister hybrids now cover majority of maize cultivation of North Eastern (NE) region of China. Seunok 335 has severe root lodging problem under storm. The author observed the lodging in the north of Shenyang, Liaoning Province in 2008, followed in the NE provinces. In addition, it was attacked by E. turcicum in the western region of Jilin Province. Both USA and China have a quarter of the world maize cultivation, each 35 million ha and produce average yield of 10.5 and 6.5t/ha, respectively. To increase maize production for feed, food and industries as well as to reduce climate changes, China’s maize cultivation and breeding must be focused on diverse hybrid development and machine harvest. The later returns stalk and leave to soil. Copies of super hybrids e.g. Seunok 335 by other companies must be discouraged. Under climate changes, breeding stable hybrids with tolerance controlled by QTL must be encouraged. Tolerance breeding has clear advantage from GMO because it shall provide a buffering effect minimizing mutation of aggressive genes. Under the climate changes, the tolerance breeding confers buffering effects of host stability. The author has bred hybrids with tolerance against major biotic and abiotic stresses. Target traits are normal field, sticky, sweet maize, bio energy maize with genes of bm3 + high sugar + leafy, and black herb maize.