Assessing above- and below-ground traits of disparate peanut genotypes for determining adaptability to soil hydrologic conditions

Crop water deficit stress contributes to more global crop loss than any other abiotic or biotic stress. To help achieve greater crop production under water scarcity, much emphasis has been placed on identifying irrigation management practices and crop genotypes for improving water stress resilience in agriculture. The objectives of this research were to: (i) quantify genotypic differences between subspecies of peanut (Arachis hypogaea L.), hypogaea and fastigiata, in root and canopy architecture, and evaluate their relationship with pod yield; and (ii) examine the response of these above- and below-ground traits of peanut genotypes to various irrigation regimes conducted in a humid climate. Field trials were implemented in 2015 and 2016 in north central Florida. Irrigation treatments included 1.9 cm per application (100%); a primed acclimation treatment consisting of 1.1 cm of water per application until mid-bloom and then 1.9 cm of water for the remainder of the season (60%PA); 1.1 cm of water per application for the entire season (60%); and a rainfed only (RF) system. Peanut genotypes included two Valencia (Arachis hypogaea L. subsp. fastigiata Waldron) market types COC 041 (PI 493631) and New Mexico Valencia C (NMVC), and two runner (Arachis hypogaea L. subsp. hypogaea) commercial cultivars FloRun™ '107′ and TUFRunner™ '511′. Genotypic total root length (TRL) and leaf area index (LAI) did not interact with irrigation treatments, but decreasing the total amount of irrigation over the growing season reduced LAI and pod yield, with no impact on TRL growth or distribution to 80 cm of soil depth. Genotypic effects influenced the TRL development over the growing season, and genotypes of subspecies fastigiata had greater TRL deep in the soil profile. However, all genotypes had similar amounts of root total surface area (TSA) distribution to 80 cm of soil depth. A positive relationship was observed between pod yield and maximal LAI in both study years, although this relationship was weak (R2 = 0.15) in 2016 when greater water deficit stress severity occurred during reproductive growth. A significant low coefficient of determination of 0.15 and 0.20 was observed for the negative relationship between pod yield and maximal TRL in 2015 and 2016, respectively. The lack of interaction between irrigation and genotype for pod yield demonstrates that peanut genotypes with more prolific root growth at depth may not necessarily have an advantage for increased amounts of water acquisition and utilization that are translated into yield.