TILLER DEVELOPMENT IN SALT-STRESSED WHEAT

Wheat (Triticum aestivum L. emend. Thell.) grain yields are highly dep endent upon the number of spike-bearing tillers produced per plant. Sa linity, drought, and other environmental stresses can greatly affect t he development and viability of tillers. We determined the effects of soil salinity on the occurrence and rate of tiller development and the incidence of tiller abortion in spring wheat cultivars, Anza and Yeco ra Rojo. Plants were grown in Pachappa fine sandy loam soil (mixed, th ermic, Mollic Haploxeralf) in outdoor lysimeters. Three salinity treat ments were imposed by irrigating with waters containing equal weights of NaCl and CaCl2 (electrical conductivities of similar or equal to 1, 12, or 18 dS m(-1)). Salinity significantly decreased the number of p rimary and secondary tillers in both cultivars. Soil water salinities greater than or equal to 7.5 dS m(-1) (mean electrical conductivity of the soil water in the rootzone during tiller development, kappa(SW)) eliminated most of the secondary tillers and greatly reduced the numbe r of T0, T3, and T4 tillers. However, the percentage of tillers produc ing spikes actually increased at kappa(SW) up to 8 dS m(-1). Higher sa linities reduced the percentage of tillers with spikes, but not as muc h as the reduction in tillers. Tiller and spike production per plant d ecreased about 0.13 to 0.15 organs for each unit increase in kappa(SW) . Of all the potential tillers these cultivars can produce, the primar y tillers on Leaves 1 and 2 (i.e., T1 and T2) were the least susceptib le to salt stress, partly because they emerged before salinity builds up during the irrigation season. Adjusting planting densities to incre ase the number of anticipated spike-bearing cuhms per unit area could help to maintain yields on salt-affected soils.