Morphological and Physiological Traits in Maize Associated with Tolerance to High Plant Density¹

Abstract

Maize (Zea mays L.) hybrids were grown at a high plant density (98,800 plants/ha) to determine the influence of several morphological and physiological traits on barrenness, the major factor limiting grain yields at high stand densities. Correlation and multiple regression analyses indicated density‐tolerant maize genotypes would be characterized by rapid completion of silk extrusion, coincidence of pollen‐shed and silk extrusion, rapid growth of the fust ear and first‐ear silk, prolificacy, reduced tassel size, and efficient production of grain per unit leaf area. Breeding populations composed of these “plant types” should allow isolation and development of high‐yielding and density‐tolerant maize genotypes.

Row spacing and fertilizer nitrogen effects on plant growth and grain yield of maize

“…An earlier study by Stivers et al (1971) demonstrated that there were more barren ears, contributing to lower yield, in wider rows (102, 76 cm) than in narrow rows (0.51 m) under drought stress conditions. However, some studies have shown no yield advantage for narrow rows (Giesbrecht 1969;Nunez and Kamprath 1969;Alessi andPower 1974, 1975) and, in some cases, high plant densities have been found to reduce kernel number per unit land area (Andrade et al 1993), decrease the number of kernels per ear (Ireminen and Milbourn 1980;Tetio-Kagho and Gardner 1988), decrease harvest index (Tollenaar 1991), and reduce the overall grain yield (Buren et al 1974;Daynard and Muldoon 1983). These reductions in grain yield have mainly been attributed to an increase in ear barrenness (Buren et al 1974).…”

Morphological and physiological traits associated with barrenness and grain yield in the maize breeding population, Iowa Upright Leaf Synthetic #1

“…Barrenness often is used as a criterion for classifying genotypes as either density tolerant or intolerant because high negative correlations between grain yield and barrenness at high plant densities have been well documented in the literature (Lang et al, 1956;Stinson and Moss, I96O; Pendleton and Seîf, I96I; Woolley et al, 1962;Stickler, 1964;Timmons et al, 1966;Rutger and Crowder, 1967;Buren, 1970). In three experiments reported'by Buren et al in 1974, correlation coefficients between grain yield and barrenness at 98,800 plants/ha ranged from -0.76 to -O.89. Stinson and Moss (I960) suggested that competition for light is a principal cause of the inability of maize hybrids to tolerate dense plantings.…”

“…Additionally, Kohnke and Miles (1951) reported that silking was delayed approximately one day for every increase of 7,000 -8,000 plants/ha. Maize hybrids intolerant of high plant densities have a longer delay in silk emergence than those that are tolerant (Moss and Stinson, 1961;Schwanke, 1965;Earley et al, 1967;Meyer, 1970;Buren, 1970;El-Lakany and Russell, 1971;Mock and Buren, 1972;Buren et al, (1974);Fakorede, 1977).…”

“…These conclusions were supported by the work of Sanford et al (1965) which demonstrated that, at high plant densities, male-sterile plants displayed more nitrogen in the ear than in the tassel compared with male-fertile plants. Mock and Buren (1972) and Buren et al (1974) indicated that densitytolerant maize genotypes were characterized by, among other traits, small tassels. These authors mentioned that large tassels suppressed ear development of plants grown at high plant densities; and according to Anderson (1971), these repressive effects were probably caused by apical dominance created by increased auxin levels in the stem.…”

“…It is important, therefore, that factors influencing barrenness be determined, evaluated and understood so successful selection of genotypes that are tolerant to high plant densities can be accomplished. Buren (1970) and Buren et al (1974) identified various morphological and physiological plant traits associated with barrenness and grain yield of maize at high plant densities, and they proposed that genotypes possessing these traits should display reduced barrenness. Once maize breeding populations composed of genotypes possessing these traits have been produced, they should be amenable to yield improvement when planted at thick densities; and the probability of isolating high-yielding, density-tolerant genotypes from these populations should be enhanced.…”