Caused by mycoplasmas, spiroplasmas, and maize fine stripe virus, maize stunt complex is endemic throughout the tropical lowlands of Central America and poses a potential danger for maize production in the region. To counteract the damaging effects of the disease in commercial maize plots, the Regional Maize Program for Central America and the Caribbean (Programa Regional de Maiz, PRM/CAC) has undertaken a collaborative stunt resistance breeding project, with the principal objective of developing high yielding, disease resistant cultivars. A tropical late white dent population (Pop. 73) and a tropical intermediate white flint population (Pop. 76), in their fifth and third improvement cycle, respectively, are being improved using an Sl-S2 recurrent selection scheme. Research conducted independently in El Salvador and Nicaragua is aimed at developing Sl lines, advancing them to S2, recombining the best segments of each population, and forming experimental synthetic varieties. Lines are evaluated in both countries during normal crop cycles under heavy disease pressure. Lines developed each cycle are tested in countries in the region facing stunt problems. Synthetics developed during the latest breeding cycles (SC3P73 N, SC2P76 N and SC3P73 R) out-yielded resistant cultivar NB-6 by 15.5%, 11.7%, and 17% respectively. A variable percentage (1-20.5%) had fewer stunted plants and ears. In disease free environments, performance of resistant cultivars was statistically similar to that of susceptible high yielding hybrids used as reference checks. Resistant cultivars show outstanding performance under disease pressure in less favored environments, without any loss in yield potential in favored ones.

English

9711|AGRIS 9702

Jose Juan Caballero

CIMMYT Publications Collection