Associations Among Nitrogen Harvest Index and Other Traits Within Two Avena Species

The partitioning efficiency of nitrogen in crop plants is measured via nitrogen harvest index (NHI), which is the ratio of the weights of grain nitrogen to total plant nitrogen. To determine what associations, if any, exist between NHI and other plant traits for oats, 40 Avena sativa lines and 52 A. sterilis collections were studied. Significant variations occurred between and within species for NHI, groat yield (GTY), groat protein percentage (GTP), groat protein yield (GTPY), straw yield (SY), straw protein percentage (SP), total plant protein yield (TPPY), harvest index (HI), and vegetative growth rate (GR). Traits significantly associated with NHI within both Avena species were HI, GTY, GTPY, SP, and heading date (HD). Uptake and partitioning of nitrogen between grain and straw were not related in A. sativa, suggesting that these two phenomena were controlled by separate physiological mechanisms. Total dry matter accumulation and not protein percentage was the major factor influencing protein yields of both grain and straw. NHI was nor correlated with either GTY or GTP in A. sativa, suggesting that selecting for high NHI may break the inverse relationship between GTY and GTP within this species