Water stress adaptation of popcorn roots and association with agronomic traits
Water stress reduces the yield of agricultural crops severely. The objectives of this study were to investigate genotypic differences between 20 popcorn lines in environments under well-irrigated (WW) and water stressed (WS) conditions to determine phenotypic, genetic and environmental relations among agronomic and root traits. The experiment was arranged in a randomized complete block design with three replications per environment. The following traits were evaluated: volume of expanded popcorn per hectare (PV), grain yield (GY), popping expansion (PE), number of rings of adventitious roots (NRAR), number of adventitious roots (NAR), number of tap roots (NTR), number of crown roots (NCR), adventitious root density (ARD), tap root density (TRD), crown root density (CRD), tap root angle (TRA), and crown root angle (CRA). Under WS, the values of the agronomic traits PV, GY and PE were reduced by 74.03, 67.15 and 28.76%, respectively. Water stress had little influence on NRAR, NAR, DR, NTR, and NCR. Due to an adaptive response to WS, increases were observed in TRA and CRA. In general, the estimates of genetic parameters evaluated under WS were higher. Negative genetic associations between agronomic traits and TRD, and CRD were observed in cultivation under WS; selection for trait PV will produce simultaneous gains in GY and PE under this regime. Under well-watered conditions, the development of genotypes with satisfactory GY and PE is difficult. This reinforces the hypothesis that root phenotypes adapted to particular environments should be identified.