Abstract
AbstractGlobal weather changes compel agriculture to be adequately productive under diverse and marginal conditions. In maize, modern hybrids fail to meet this requirement. Although breeding has achieved spectacular progress in grain yield per area through improved tolerance to stresses, including intense crowding, yields at low plant population densities remain almost unchanged. Stagnated plant yield potential renders hybrids unable to take advantage of resource abundance at lower populations, designating them population dependent. Consequently, the optimum population varies greatly across environments. Generally, the due population increases as the environmental yield potential gets higher. As a remedy, relatively low populations are recommended for low-input conditions leading to inappropriate population in occasional adequacy of resources and considerable yield loss. For example, for a rain-fed hybrid tested at one location across 11 seasons, crop yield potential and optimum population on the basis of the quadratic yield-plateau model varied from 1,890 to 8,980 kg/ha and 4.56 to 10.2 plants/m2, respectively, while 100 % yield loss is computed in the driest season if the optimum population for the most favorable season is used. The article reviews the consequences in terms of crop sustainability under widely diverse environments imposed by climatic changes and proposes crop management strategies to address the situation. The major points are: (1) variable-yielding environments require variable optimum populations, (2) population dependence is an insurmountable barrier in making a decision on plant population, (3) farmers suffer from considerable yield and income loss, (4) estimating the less population-dependent hybrids among the currently cultivated ones is a major challenge for agronomists, and (5) the development of population-neutral hybrids is a fundamental challenge for maize breeding. Honeycomb breeding is a valuable tool to pursue this goal since it places particular emphasis on the so-far stagnated plant yield potential that is essential for population-neutral hybrid development.
Highlights
According to the general conclusion emerging from the published data, the higher the yield potential of the environment, the higher the due plant population density should be
They reported on quadratic equations indicating that the two hybrids were of similar Crop yield potential (CYP) but of different OP
Even though breeding has resulted in spectacular achievements for grain yield per area, modern hybrids fail to meet this presupposition, and the issue is of utmost importance
Summary
Spatial and temporal heterogeneity of the environment may cause a considerable variation in crop yields (Williams et al 2008; Rusinamhodzi et al 2011). Modern hybrids (Fig. 1) are usually population dependent (Tokatlidis et al 2001, 2011), with the ideal plant number per area depending on several factors, including water availability, soil fertility, hybrid maturity group, and row spacing (Sangoi et al 2002) Hybrids accomplish their per-area yield potential at high and narrow spectrum of populations, i.e., they follow the quadraticplateau regression model (Van Roekel and Coulter 2011). Tokatlidis and Tsialtas (2008) studied this artifact statistic and discovered that, even though it is greatly affected by the level of the lowest population included in the analysis, hybrids’ rank does not change and PYP is a solid criterion to comparatively estimate the hybrids for yield potential at the single-plant level. It is hard to reach a particular recommendation on appropriate plant population, devoid of the risk of considerable yield loss and limitation of farmers’ income
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