Screening of Popcorn Genotypes for Drought Tolerance Using Canonical Correlations

Abstract

Getting around the damage caused by drought is a worldwide challenge, particularly in Brazil, given that economy is based on agricultural activities, including popcorn growing. The purpose of this study was to evaluate popcorn inbred lines under water stressed (WS) and well-watered (WW) conditions regarding agronomic attributes, root morphology, and leaf “greenness” index (SPAD index), besides investigating the viability of indirect selection by canonical correlations (CC) of grain yield (GY) and popping expansion (PE). Seven agronomic, six morphological root traits were evaluated and SPAD index at five different dates during grain filling. The WS (−29% less water than WW) affected significantly the GY (−55%), PE (−28%), increased the brace and crown root density, and more vertically oriented the brace and crown angles. Higher SPAD index is associated with a higher yield, and these measures were the only ones with no significant genotype × water condition interaction, which may render concomitant selection for WS and WW easier. For associating the corrections of the different traits, CC proved to have better potential than simple correlations. Thus, the evaluation of SPAD index at 29 days after the anthesis showed the best CC, and based on the previous results of SPAD index, may be used regardless of the water condition.

Supporting Physiological Trait for Indirect Selection for Grain Yield in Drought-Stressed Popcorn

“…In agricultural crops, soil water restriction, caused by the irregular distribution of rainfall during the growth and development of agricultural crops, has a strong impact on yield [ 1 , 2 , 3 , 4 ]. Yield losses caused by drought events have become recurrent [ 5 , 6 , 7 ] and to find measures to minimize them is a challenge nowadays for global agribusiness and, in particular, for Brazil, where agriculture is a key component of the economy [ 8 ]. The impact of water restriction depends on the intensity and duration of a dry spell, as well as on the phenological stage of the plant when it occurs [ 1 ].…”

“…Methods to assess leaf senescence based on the spectral properties of leaves have been used, i.e., measurements of leaves with a portable chlorophyll meter (SPAD index) and an equipment that determines the normalized difference vegetation index (NDVI index) (spectral vegetation indices), as well as the canopy [ 3 , 32 ]. However, the effectiveness of phenotyping methodologies for popcorn lies partly in the possibility of applying them at the critical stages of grain production [ 1 , 15 , 17 ] and popping expansion [ 8 , 22 , 33 , 34 ].…”

“…For maize, different statistical approaches have been used to identify the relationship between the morpho-agronomic traits, as well as those calculated as leaf spectral properties, namely: simple correlation [ 35 ], path analysis [ 36 ], GT-Biplot [ 18 ] and canonical correlation [ 8 ]. However, with the exception of simple linear correlation, these methods include the analysis of irrelevant variables for the model, which interferes with the assumptions for the predictors.…”

Water Use Efficiency in Popcorn (Zea mays L. var. everta): Which Physiological Traits Would Be Useful for Breeding?

“…Some studies found that root length, biomass and density can be considered characteristics of interest for the selection of genotypes under soil water stress, for allowing greater soil exploration in lateral and vertical directions [ 43 , 44 , 45 ]. It is no coincidence that these characteristics are related to greater water use efficiency in popcorn [ 46 ]. Among mature maize plants in the field, the most productive were the genotypes with the highest RL and RDW [ 29 , 47 ].…”

“…This means that steeper roots with straighter profiles are more adaptable to draw water from deeper soil layers. Genotypes with these root characteristics may have advantages in the exploration of subsurface soil layers, allowing greater water uptake [ 18 , 46 , 48 ]. Under drought conditions, [ 19 ] showed that the most productive genotypes were those with deeper roots.…”