ablishment process of the Honeycomb field selection designs (Figure 1 and Figure 2), conceived to accurately evaluate individual plants through elimination of the masking effects of soil heterogeneity and interplant competition, have been extensively treated in . A subsequent article  defined interplant competition as the interference with the equal sharing of growth resources among plants because of genetic and acquired differences. It was demonstrated that in the crop stand, the gains from competition do not overcompensate for the losses from it. In the prevalence of big genetic or acquired differences in the crop stand, crop yields are reduced, a concept of great relevance as to the reasons for the observed gap between actual and potential yields. The article established the use of the Coefficient of Variation (CV) of single-plant yields to measure the acquired and the genetic competition. Under dense stands, CV strongly correlates with crop yield (the lower the CV, the lower the unequal sharing of resources within the crop stand, the more uniform the stand, and the higher the yield). An early verification of this notion appeared in  and . Under conditions that exclude interplant competition, CV was found to reflect the departure from normality of the yield distribution and to estimate the load of deleterious genes in breeding populations .
A further essential point was the analysis of the crop yield potential into three independent genetic components [19,20] estimated reliably in the absence of the masking effects of interplant competition and soil heterogeneity. The three components were defined as (i) the yield potential per plant, estimated by the mean progeny yield , (ii) the stability, estimated by the standardized progeny mean yield , where and represent the mean and the standard deviation of the entry/line where each plant belongs, and (iii) the adaptability or responsiveness to inputs, estimated by the standardized selection differential . The independence among the three genetic components was key for predicting for the first time the possibility to develop monogenotypic cultivars that are density-neutral (i.e., capable to attain maximal yields under a wide range of planting densities), while simultaneously possessing high yields per hectare under standard crop stands. The existence of density-neutral cultivars, further verified in maize , a crop whose hybrid performance is known to be highly density-dependent, demonstrated conclusively that density ceases to represent a component of crop yield potential, an idea that had been a widespread working assumption during the recent past (e.g., ). The same article  first presented the concept of ‘nonstop’ selection as an essential component of a comprehensive breeding procedure.
The partitioning of crop yield potential was incorporated in a novel software package designed to analyze data from honeycomb breeding experiments .
Through exploitation of the unique properties of the Honeycomb designs, it was subsequently possible to condense the three components of crop yield potential to two [24,25,26]. The two components are the Plant Yield Index PYI = (Figure 2; Design Code 4 exemplifies plants whose yield per plant is compared to the mean yield of the surrounding plants of the 30 remaining entries in the grey area), measuring with accuracy individual plant yield potential, and the Coefficient of Homeostasis CH = , measuring yield stability or homeostasis. The CH incorporates every factor affecting stability of performance, including heritability, heterozygosity, biotic and abiotic stresses, high planting densities, and any other source contributing to yield variability. The product of the two components measures the plant’s crop yield potential and constitutes the first of two novel equations used in the selection process.
The second equation results by replacing the parameter PYI by the Line Yield Index LYI = , where is the mean yield of the progeny line (lines 1 to 31 in this case) and the mean yield of all plants in the trial:
The concept of nonstop selection find