ANALYSIS OF MAIN-SPIKE YIELD COMPONENTS IN SALT-STRESSED WHEAT

Grain yield potential of wheat (Triticum aestivum L.) main spikes is genetically determined and depends upon the number of spikelets per spike, the number of kernels per spikelet, and the weight of individual kernels. Environmental factors may interact with the genotype to influence the expression of these components. This study was initiated to determine the effects of salinity on main-spike yield components of two Mexican semidwarf, hard red spring wheat cultivars, Yecora Rojo and Anza. Plants were grown in greenhouse sand cultures irrigated four times daily with modified Hoagland's solution. Two saline treatments with osmotic potentials (psi(s)) of - 0.65 and - 0.85 MPa were imposed by adding NaCl and CaCl2 to the base nutrient solution. The electrical conductivities of the saline irrigation waters (EC(iw)) were 14.3 and 18.1 dS m-1, respectively. These treatments were compared to a nonsaline control treatment at - 0.05 MPa (EC(iw) = 2.0 dS m-1). Six main-spike yield components were measured: spike length, spikelets per spike, kernels per spike, kernels per spikelet, individual kernel weight, and total kernel weight per spike. The first three parameters decreased in response to salinity. Kernel number per Anza spikelet was unchanged by salinity. Compared with the controls, kernel number per Yecora Rojo spikelet increased at - 0.65 MPa and decreased at - 0.85 MPa. At - 0.65 MPa, decreases in kernel numbers per spike of both cultivars were offset by increases in kernel weight, particularly in the central spikelets. As a result, grain yield per main spike was 12 to 15% higher than in the nonsaline controls. Stimulation of main-spike yield by salinity suggests that in those salt-affected areas where tillering capacity may be reduced, wheat production may benefit from higher planting density.