UC Riverside

It was reported that wheat cultivars with reduced metaxylem diameters in roots produced higher grain yields compared to those with larger metaxylem diameters under drought conditions, but not under well-watered conditions. Multiple dosages of rye 1RS translocations in wheat were reported to reduce root metaxylem diameter. The dosage number of 1RS translocations was inversely proportional to the root metaxylem diameter.

Two greenhouse experiments and a field experiment were carried out at University of California, Riverside in 2012 and 2013 under well-watered and terminal drought treatments to test whether translocation lines of wheat cv. Pavon 76 containing 1(RA1), 2 (RA2 and RD2), and 4 dosages (RAD4) of 1RS produced higher grain yields than the control with zero dosage (R0) under terminal drought. Drought in the field experiment reduced grain yield significantly. Grain yield of RA2 (23.9 g-1) was significantly greater than those of RD2 (20.6 g-1) and RAD4 (17.3 g-1) under well-watered field conditions. Also, grain yield of RAD4 was significantly less than those of RA1, R0, and RD2 under well-watered conditions. Under drought field conditions, only significant difference in grain yield was found between RA1 (14.7 g-1) and RAD4 (12.4 g-1). Harvest index was significantly greater in well watered (44.2%) than in droughted (34.6%) field conditions. On average, genotype R1 (42.3%) and RA2 (40.6%) had higher harvest index than RD2 (38.3%) and DAR4 (35.5%) in the field. Also, R0 (40.2) and RD2 (38.3) had higher harvest index than DAR4. In general, Pavon 1RS.1AL carrying double doses of 1RS showed higher grain yields under wet treatments. Pavon 1RS.1AL-1RS.1DL carrying four doses of 1RS produced largest shoot and root biomasses, but relatively had least grain yield. There was a negative correlation between the grain yield loss and metaxylem diameter in roots at mild stress levels (~36%).