Lodging resistant tropical maize inbred lines from Tuxpeño

-- S. K. Vasal, G. Srinivasan and F. Gonzalez C.

Root lodging due to poor and/or shallow root structure is a common problem in tropical maize growing environments. At CIMMYT, while evaluating our inbred lines for their per se performance, we accidentally discovered a very valuable source for lodging resistance in our Tuxpeño germplasm. During 1988 and 1990, we experienced a severe hurricane at our lowland tropical experimental station at Poza Rica, México during the main growing season (June-Nov.). The hurricane which hit the maize crop just before flowering practically bulldozed the entire farm. To our pleasant surprise, we identified a few patches of maize standing here and there undisturbed by the hurricane. Upon checking our pedigree, we found that they had all come from a single source going back to Population 21 Fam. 219 which we had identified in our previous studies as a good source family for producing superior inbred lines and also as possessing good combining ability.

Three inbred lines arising out of Pop. 21 Fam. 219 have recently been announced in 1991 by the Maize Program, CIMMYT for use by national programs and maize breeders worldwide. They are: 1) CML 9 (Pop. 21 C5 HC219-3-1-B-###), 2) CML 10 (Pop. 21 C5 HC219-3-2-2-3-B-2-2-###, and 3) CML 11 (Pop. 21 C5 HC219-3-2-2-3-#-7-1-B-4-1-B) ["CML" stands for CIMMYT maize line and HC in Spanish for full-sib family].

CML 9 has been extensively used as a tester line in our hybrid research program and has been found to possess excellent combining ability. These lines are characterized by good stalk quality, a vigorous root system with strong brace roots, slightly broader leaves, and a fair degree of tolerance to most of the tropical foliar diseases. CML 9 which is an early generation line is fairly high yielding and is being used extensively in developing lodging resistant germplasm at CIMMYT. The salient characteristics of the three lines are furnished in Table 1. Small quantities of seeds of these lines are available upon request.

Table 1. Salient features of the lodging resistant lines.
Characters CML 9 CML 10 CML 11
Maturity Late Late Late
Grain color White White White
Grain type Semident Semident Semident
Yield (t/ha.) 4.5 2.0 2.9
Growing degree days 1126 1143 1085
Plant height (cm) 147 142 152
Ear height (cm) 69 73 77
Ear rot (1-5)* 1.9 2.3 2.2
Rust (1-5) 1.5 1.4 1.7
Maydis (1-5) 2.2 1.8 1.9
* Rating on a scale of 1-5. 1 = Resistant, 5 = Susceptible

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