Developing Drought and Low-Nitrogen Tolerant Maize Symposium Abstracts

Poster 1-13

TRIAZOLE PRIMING OF MAIZE SEED TO ENHANCE DROUGHT TOLERANCE DURING FIELD ESTABLISHMENT

V. Souza Machado^1, G.O. Edmeades², A. Ali¹ and I. Aguilar-Mariscal³

¹ Dept. Horticulture, University of Guelph, Guelph, Ontario, Canada
² CIMMYT, Int., Apdo. Postal 6-641, 06600 Mexico D.F., Mexico
³ Colegio Superior Agropecuario, Iguala, Edo. Guerrero, Mexico

Lowland tropical maize environments are characterized by unreliable rainfall distribution at planting time. Triazoles are plant growth regulators which moderate the effects of drought and high temperatures. We evaluated the triazole ‘Paclobutrazol’ as a seed primer on two maize cultivars in 1994 and on five maize cultivars in 1995 in field trials conducted at Tlaltizapan, Morelos and at Cocula, Guerrero, and in greenhouse studies at the University of Guelph.

In the 1994 trial series, seeds of hybrids ‘P 3288’ and ‘NK TB 8101’ were primed with Paclobutrazol 50 alone and in combination with Ancymidol 25, and grown under severe and moderate drought stress conditions in the dry winter season. At Tlaltizapan, the triazole treatments, compared with the non-primed check, delayed seedling emergence by 2.4-3.2 days, reduced plant height by 4%, delayed anthesis by 1.4-2.0 days and reduced grain yield by 11-17% across both drought treatments. At Cocula similar results were obtained, though yield differences were non-significant due to a high coefficient of variation.

In the 1995 trial series, three cultivars (‘CML8 x CML9’, ‘CML19 x CML27’, ‘La Posta Sequía C3‘, ‘SIWA’ and ‘SIBA’) (the last three from CIMMYT’s drought breeding program), were seed treated with Paclobutrazol 80 imbibed, Paclobutrazol 20 seed coated, and in combination. The two field trials at Tlaltizapan involved a seedling survival trial with a gradation in levels of irrigation during the establishment phase and a mid-season drought stress trial. The seed coated treatment showed no significant response in either trial; the imbibition treatment reduced surviving seedling counts by 15-21% under severe water stress, slowed the rate of emergence, and resulted in non-significant reductions in biomass and grain yield. In greenhouse experiments at Guelph on the same genotypes and seed treatments, Paclobutrazol imbibition treatment delayed emergence, reduced seedling height and fresh weight by 30% and 25% respectively, and gave inconclusive results under heat and drought stress. No differences were noted between the seed coated treatment and the ‘check’. We conclude that Paclobutrazol, as an imbibed seed treatment for tropical field maize, cannot be recommended at this stage.