Preanthesis Tiller Mortality in Spring Wheat

Abstract

A primary determinant of yield in wheat (Triticum aestivum L.) is the number of spike‐bearing tillers per unit area. Many tillers that emerge do not survive to produce spikes. This study was conducted to determine the point in development when tillers begin to senesce and to examine how premature senescence is affected by water deficits and plant population. Cultivars Edwall and Waverly were planted in a 2‐yr field study at two plant densities (168 and 84 kg ha−1 in 15‐ and 30‐cm rows, respectively) and with both irrigated and nonirrigated treatments. The Haun stage of leaf development was monitored weekly on five plants per plot. Tiller mortality was monitored from tiller emergence until maturity. For tillers destined to die prematurely, a reduced rate of leaf emergence and development was evident immediately after tiller emergence. The majority of tillers senesceduring main stem extension, while almost no tillers were lost during grain filling. The maximum Haun stage reached by senescing tillers was normally ≤3 for all tillers excepthe coleoptile (TO) tiller. For this tiller, the maximum Haun stage was ≤4. Premature tiller senescence occurred in both irrigated and nonirrigated plots and was greatest at the higher plant density. Water deficits increased the number of tillers that died but did not affect the stage at which senescence occurred. Tillers that emerged late during plant development were most likely to senesce prematurely.