Principles of Plant Genetics and Breeding

BREEDING FOR RESISTANCE TO ABIOTIC STRESSES 393
The heat shimmered above the dry earth, engulfing all in
its wake. The black clay soil was deeply cracked, and
like a cosmic vacuum cleaner, the sun sucked the last
hint of moisture from its depths. Yet this desolate landscape
was not without life. A crop of sorghum stood
defiantly, thrusting its red grain into the copper sky. It
was the dry season in southern India and no rain had
fallen for many weeks. The crop was almost ready to
harvest, but the yield would be low due to the severe
drought (Figure 1). I walked through my experimental
plots at the International Crops Research Institute for
the Semi-Arid Tropics (ICRISAT) on the outskirts of
Hyderabad. A young Indian scientist accompanied me
on this stroll through our 280 plots. We stopped briefly
at each plot, noting if any leaves still remained alive.
We were examining a population of sorghum lines that
varied in the stay-green drought-resistance trait.
Plants containing the stay-green trait maintain more
Figure 1 Harvesting the sorghum experiment in southern green leaf and stem under drought compared with
India at the end of the dry season. The B35 variety
senescent (non-stay-green) plants, resulting in stronger
displayed remarkable resilience under extremely dry
stems and higher grain yield. In most plots we found all
conditions.
the leaves had died. It was not unusual to find whole
plots laying on the ground, their stems greatly weakened
by the drought. I will never forget what happened next.
Looking up from my notebook, I was stunned to see a plot of sorghum with a number of large green leaves and strong green
stems (Figure 2). Balancing on the end of these stems were large panicles yielding about three times as much grain as the other
plots. How could this be? Our field plan revealed that this particular line was B35, a stay-green line from Ethiopia that was first
documented by Dr Darrell Rosenow, a plant breeder at Texas A&M University. B35 is derived from a durra landrace, an ancient
(a) (b)
Industry highlights
Discovering genes for drought adaptation in sorghum
Andrew Borrell 1 , David Jordan 1 , John Mullet 2 , Patricia Klein 2 , Robert Klein 3 , Henry Nguyen 4 , Darrell Rosenow 5 , Graeme
Hammer 6 , and Bob Henzell 1
1 Department of Primary Industries and Fisheries, Hermitage Research Station, Warwick, Queensland 4370, Australia;
2 Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, TX 77843, USA; 3 USDA-ARS
Southern Agricultural Research Station, College Station, TX 77843, USA; 4 Plant Sciences Unit and National Center for
Soybean Biotechnology, University of Missouri, Columbia, MO 65211, USA (previously Texas Tech University, Lubbock,
USA); 5 Texas A&M Agricultural Research and Extension Center, Lubbock, TX 79403, USA; 6 School of Land and Food,
University of Queensland, Queensland 4072, Australia
Figure 2 Photographs of (a) senescent and (b) stay-green sorghum taken on the same day just prior to harvesting in
the field experiment. The B35 stay-green variety is derived from a durra landrace from Ethiopia.