Effect of Mixed-Salt Salinity on Growth and Ion Relations of a Barnyardgrass Species

Recent investigations of the plant genome have revealed a large degree of similarity among cereal crops (specifically within the family Triticeae) and other related grass species. Recognition of the close genetic relationship among the grasses indicates that more exotic species, such as weedy grasses, may be exploited by plant breeders to enhance biotic/abiotic stress tolerance in cereal crops. Echinochloa crus-galli (L.)1 Beauv. (barnyardgrass), a wide-spread, persistent C4 weed species of agricultural importance, is reported to tolerate high levels of salinity. Growth and ion relations were studied in barnyardgrass using mixed-salt salinity (with final electrical conductivities (ECi) of 3 (control), 7, 11, and 19 dS m−1 in the irrigation water) to determine whether the mechanism(s) for its salt tolerance are similar to those previously reported for other cereal crops. Such a finding would indicate that barnyardgrass may possess valuable genetic traits. Ion accumulation and ion selectivity ratios in the various treatments were determined from oven-dried shoot tissue. Significant (P < 0.01) linear regressions were obtained between either fresh weight or plant height and ECi. The point of 50% reduction (C50) in fresh weight was predicted to occur at about 13.9 dS m−1; the C50 value for plant height was at about 22.9 dS m−1. Statistical analysis of calculated Gapon constants for potassium (K)/sodium (Na) indicated that ion selectivity was not affected until after 11 dS m−1. Calcium (Ca)/Na selectivity was not significantly affected by salinity. We concluded that, similar to some cereal crops, barnyardgrass maintains growth under Received 20 July 2004; accepted 3 November 2005. Address correspondence to Clyde Wilson, United States Department of Agriculture, Agricultural Research Service, George E. Brown Jr. Salinity Laboratory, 450 West Big Springs Road, Riverside, CA 92507, USA. E-mail: [email protected] 1Mention of company names or products is for the benefit of the reader and does not imply endorsement, guarantee, or preferential treatment by the USDA or its agents. 1741 D o w n l o a d e d B y : [ U S D A N a t l A g r i c u l t u l L i b ] A t : 2 3 : 5 6 1 2 M a y 2 0 0 9 1742 C. Wilson and J. J. Read saline conditions by maintaining high K/Na ratios, possibly because of better membrane integrity due to high Ca selectivity.