# New Parameters for Seeding Vigor Developed via Phenomics
## 1 Introduction  
Early seedling establishment in rice (_Oryza sativa_ L.) is a crucial trait to compete for light, air, and water for better tolerating various abiotic stresses. It also contributes to subsequent tillering quality [1]. Thus, it can highly affect the grain yield [2]. [PERSON] et al. [3] reported that early vigor has a very strong correlation with yield (0.84). Early seedling establishment is described in many research papers as seedling vigor and measured using several traits, such as primary/secondary filler, shoot length, biomass, root-related traits, and leaf area index [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13].  
With the fact that the yield itself is one of the most poorly inherited traits in crop breeding [14], it would be very advantageous to invest in data collection during the early stage via examining seedling vigor. Among those traits for early seedling vigor, the majority of research has studied plant height and tillering because they are associated with yield. Plant height can help compete for light and indirectly affect biomass, which has a high impact on grain fill and grain weight. Tillering is highly related to the panicle number and eventually grain number. Other traits such as roots are also highly associated with the yield, while they are laborious and time-consuming to measure.  
The labor-intensive and costly conventional phenotyping was the only method until the advent of high throughput phenotyping [15]. However, it has not been widely adapted in breeding programs.  
In rice, there are two research papers that have been published that collected data in the greenhouse [16] and field [17] using mature plants. However, the beauty of phenomics is the non-destructiveness, which means that the same objects can be repeatedly measured in different time intervals. Further, it can snap the data of many samples within a very short period of time very accurately and precisely. These are excellent features for collecting data in the early stage since the growth stage shift is fast in that stage. However, previous studies on seedling vigor only collected data once [7; 12; 13]. Although two data points were collected in one study, it did not examine the difference between the two data points [5]. As [PERSON] et al. [18] concluded that the quantitative trait loci (QTLs) on chromosome 1 for different traits, including projected plant height, panicle number, and panicle length, suggest the pleiotropism and or tight linkage of those traits, sharing several traits in the same region on chromosome 4 might be explained by pleiotropism as well.  
There are several growth stage shifts, which means that many changes are involved in this time period. Thus, even the same trait, such as plant height and biomass, can be very different within this time span. Further, there is no research on the growth rate that has been conducted by measuring two different time points for growth comparison, which would enable researchers to understand what really occurs in the early stage. Hence, the objective of the current study is to measure the growth rate using plant height and green area which are highly associated with yield in second and fourth week in order to find out if these traits are related with any QTLs. The result would help us to understand how each phase of vegetative growth in the early stage moves. Furthermore, it would be the true feature of seedling vigor since it can measure the growth rate within a two to four-week time span.