The GIGANTEA early flowering promoting allele was detected only in GR5, GR10, and Frieda cultivar. However, further experimentation on the aforementioned landraces is needed, in order to examine the predictive power of those molecular markers, and their potential implementation in white lupin breeding programs. Alleles that confer resistance to anthracnose, were previously found only in Ethiopian landraces, which are distinctly related to European improved germplasm . Resistance conferring alleles, located in antr04_1/antr05_1 and antr04_2/antr05_2 loci, were also detected in the Greek landraces examined, with GR23 and GR25 from Andros, having both of them in their genome . Summarizing these results, molecular markers linked to important agronomic traits have been identified in white lupin germplasm from the Greek rural areas. It will be significant to confirm the association of these markers to the relevant plant phenotype in further studies.

This will be crucial for the utilization of the relative landraces when is necessary , as sources of the responsible alleles in lupin breeding. The global population is expected to reach 8 billion by 2025, which will double future food demand . To meet this demand, crop yield must be increased without increasing the cultivated area. Previously, many studies have been carried out on upgrading crop yield and quality by researchers , such as increasing plant population density and nitrogen fertilizer use. However, a suitable population structure requires not only sufficient individuals per unit area but also the rational distribution and uniform development of individuals in the field for maximum utilization of natural resources . Crops grown with high population density that exceed a certain threshold will encounter competition from neighboring vegetation, which restrains plant growth and yield due to limited light, water, and nutrients . The alteration of photomorphogenic plant responses to plant population density could be used to increase the yield . The critical variable regulating plant growth and yield at different plant population densities is light.

Shade avoidance and shade tolerance are the two contrasting strategies adopted by plants in response to competition for light. Plants perceive low photosynthetically active radiation as an early signal of neighbor competition through phytochrome photoreceptors, which in turn induces the shade-avoidance responses . Generally, a SAR involves the elongation of internodes, reduction in branches, or decrease in leaf number, chlorophyll a/b ratio, or photosynthetic rate that leads to the reallocation of assimilates to stem elongation instead of root and leaf growth, and therefore causes significant decrease in yield . These responses are regulated by phytochromes , which sense decreases in the red/far-red ratio in dense populations and initiate the SAR . At low red/far-red ratios, the phytochrome gene decreases that in turn induce PHYTOCHROME INTERACTING FACTOR accumulation , which regulates the expression of genes associated with SAR. Previous studies have attempted to reveal the mechanisms underlying SAR .

However, the major challenge is to extend our knowledge of this mechanism in plants to develop novel strategies to improve crop yield at high population density. In view of the findings of our investigation and previous research, many useful measures could be implemented to minimize the effect of SAR on crops . The pepper plants were taller and there were fewer branches in double to triple the normal plant population density than normal plant population . Therefore, increased within-row spacing may be a useful measure of plant stand establishment through initiating the effect of SAR, which enables farmers to increase the harvest index or produce high yield with normal population densities. The peanut is a leguminous crop and an important source of oil and protein for humans, which is cultivated worldwide in tropical and subtropical regions. In China, peanut is grown on more than 5.0 × 106 ha to ensure the supply of edible oil . Traditional planting patterns mainly involved double- and multi-seed sowing, which lead to plant competition, lodging, and low yield.

However, to decrease the competition among plants and increase peanut yield, the Shandong Academy of Agricultural Sciences developed a high-yield cultivation technique for monoseeding precision sowing, which was ranked as the main technology by the Ministry of Agriculture and Rural Affairs for five consecutive years from 2015–2019 and promulgated as the national agricultural industry standard . Many scientists have conducted studies to reveal the yield-increasing mechanisms of monoseeding precision sowing that are involved in ontogenetic development and population structure . However, we assumed that the monoseeding pattern increased the peanut yield through the regulation of SAR. Therefore, the purpose of this study was to decipher the physiological and molecular yield-increasing mechanism of monoseeding. As shown in Table 1, the number of nodes shown significantly different between 2018 and 2019, while the main stem height, main stem diameter and number of branches were insignificant.