Salinity Effects on Growth, Shoot-ion Relations, and Seed Production of Lesquerella fendleri

Lesquerella fendleri (Gray) S. Wats., a native of the arid and semiarid regions of southwestern US, has been proposed as an important industrial seed oil crop (Thompson and Dierig 1988). Intensive breeding and agronomic research efforts at the US Water Conservation Laboratory have been directed towards domesticating and commercializing the crop (Dierig et al. 1993; Coates 1994; Brahim et al. 1996; Dierig et al. 1996; Nelson et al. 1996). Information on the management of lesquerella under saline conditions is limited to a two-season (1993– 4 and 1994–5) field trial conducted by Leland E. Francois at the Irrigated Desert Research Station located at Brawley, CA (Grieve et al. 1997). Six salinity treatments were imposed by adding NaCl and CaCl2 (2:1 molar ratio) to Colorado River water. Electrical conductivities of the irrigation waters (ECi) ranged from 1.4 to 10.0 dS m-1. Both biomass production and seed yield were significantly reduced by salinity, although salt stress had no effect on either the content or the composition of the oil. Based on the combined seed yield data for both years, the salt tolerance threshold (the maximum allowable EC e without a yield decline) was 6.1 dS m-1 and the C50 (ECe value that would result in a 50% yield reduction) was 9 dS m . [As an approximation: ECe = 1.5 ECi]. Each unit increase in salinity above the threshold resulted in a 19% decrease in yield. Under nonsaline control conditions in the Brawley plots (EC i = 1.4 dS m-1), lesquerella was a strong calcium accumulator, and as external calcium increased in concert with salinity, leaf-Ca2+ significantly increased. In response to Clsalinity, leaf-Clincreased three-fold as EC i increased from 1.4 to 10 dS m-1. Large increases in external Na had no effect on leaf-Na. Sodium levels in lesquerella leaves were at least an order of magnitude lower than leaves of other crucifers grown at the same location with the same compositions of Cl--dominated salinity (Francois and Kleiman 1990; Francois 1994). Lesquerella apparently possesses an unique and effective exclusion mechanism that limits the accumulation of potentially toxic levels of Na+ in the leaves. One objective of the current study was to determine the response of lesquerella to sodium sulfate-dominated irrigation waters that are typical of the saline drainage waters commonly encountered in the San Joaquin Valley of California. Lesquerella was evaluated as a crop that could fill a niche in the drainage water reuse system where only moderate tolerance is required. A second objective was to identify and isolate individuals that exhibited salt tolerance and use this germplasm for establishing a base population for breeding more salt tolerant lesquerella.