Improving Corn Population for Grain Yield and Resistance to Leaf Blight and Stalk Rot¹

Abstract

Estimates of among and within half-sib family varl. ance components for disease scores in each of two corn (Zea mays L.) populations were obtained from artificially inoculated experiments in 1, 2, or 3 years. These estimates were used to predict response to mass, half-sib, and Ss election for resistance to northern corn leaf blight (caused by Helminthosporium turcicum Pass.), Diplodia stalk rot [caused by Diplodia maydis (Berk.) Sacc.], and anthracnose leaf blight and stalk rot [caused by Col. letotrichum graminlcola (Ces.) Wils.]. In addition, among half-sib family variance component estimates for yield were obtained from unlnoculated experiments for the same families.Genetic correlations among yield and reactions to the four diseases were estimated.Per-year predicted gains in ieaf blight resistance for mass selection with pollen control were greater than for either S~ or half-sib family selection (with 20 plants per family). Per-year predicted gain for mass selection-for stalk rot resistance was greater than that for half-sib family selection (20 plants per family), For a given selection intensity and effective population size, predicted gain in stalk rot resistance for mass selection with pollen control is about equal to that for S~ selection at a great reduction in the number of plants rated for disease reaction and at no increase in the required number of hand pollinations.Genetic correlations between grain yield in the absence of disease and disease reactions were all near zero and nonsignificant. All significant genetic correlations among disease reactions were positive. These results suggest that mass selection would be the most efficient method of improving disease resistance in corn populations and that such improvement would not affect yield potential of the populations if adequate effective population size is maintained.

Change in heritability estimates due to half-sib family selection in the maize variety Pahari

“…Analysis of variance (ANOVA) based on a randomized complete block design was computed according to format (Table 1) for the data of each year and trait (Milles et al, 1980) to derive mean squares for HS families using the MSTATC computer package (Director Crop and Siol Science Department, Machigan State University, Version 2.00). Estimates of genotypic and phenotypic components were calculated from ANOVA and used to calculate heritability on an entry-mean basis (Penny and Elbert, 1971;Carson et al, 2004) as follows:…”

Inheritance of resistance to anthracnose stalk rot (Colletotrichum graminicola) in tropical maize inbred lines

“…Symptoms also include discoloration of pith and stalk breakage (Miles et al 1980, Bergstrom and Nicholson 1999, Muimba-Kankolongo and Bergstrom 2011. Usually, these symptoms start immediately after flowering.…”

Response to Recurrent Selection for Resistance to Striga hermonthica (Del.) Benth in a Tropical Maize Population

“…Recurrent selection involves systematic testing and selection of desirable progeny derived from a population followed by recombination of the selected progeny to form an improved population. This type of selection method has been used successfully for increasing resistance in maize to diseases ( Jenkins et al, 1954;Miles et al, 1980Miles et al, , 1981Ceballos et al, 1991;Lambert and White, 1997) and European corn borers (Ostrinia nubilalis Hübner) (Tseng et al, 1984;Klenke et al, 1986). So far, the use of recurrent selection for improving resistance to parasitic plants in maize and other cereals has been limited.…”