Assessing the Impact of Salinity On Citrus Rootstocks In the Lower Rio Grande Valley.

Citrus is an economically important crop in Texas, worth approximately $50 million annually, with production concentrated in the four-county region of the Lower Rio Grande Valley (LRGV) in south Texas.  In recent years, the citrus industry in the U.S. and the LRGV, in particular, has been facing numerous challenges such as emerging diseases and recurrent droughts.  Increased incidence of water deficits and other drought-related issues such as increased soil salinity have prompted the need for efficient water management strategies, including alternative water sources, and adoption of stress tolerant varieties to mitigate the effects of drought, salinity, and to meet the needs of a rising population along the U.S.-Mexico border.

The main goal of this study is to assess the salinity tolerance of citrus rootstocks that are currently available for commercial citrus production in the LRGV, and to determine if low-quality water can be safely used for citrus irrigation.  Among the requirements for rootstocks grown in the LRGV are tolerance to calcareous soils, Citrus Tristeza Virus (CTV) resistance, and salinity tolerance. The standard rootstock used when soil conditions are alkaline and clayey has been the Sour Orange rootstock; however, alternative rootstocks are being considered due to its susceptibility to CTV.  There are several rootstock varieties that are CTV resistant, yield high quality fruit and are tolerant to calcareous clay soils; C-22 and C146 rootstocks are among the most promising of these new varieties.  This experiment was conducted using a simulated brackish water solution applied at 5 levels of electrical conductivity to assess salinity tolerance, physiological changes and general tree health when exposed to salinity.  Here we will discuss the salinity tolerance of the three citrus rootstocks studied and the implications for the citrus industry.