Differential responses of barley, durum and bread wheat to high levels of soil boron
1997
Yau, S.K. (ICARDA, Aleppo (Syria))
Boron can be phytotoxic, causing yield reduction, when present in slightly above normal concentrations in the soil solution. Boron toxicity, caused by inherently high levels of B in soils or by using irrigation water high in B, has recently been found to occur in many dry areas of West Asia and North Africa (WANA). In view of the importance of barley, and durum and bread wheat in WANA, especially in semi-arid and high-altitude areas, work to identify B-toxicity tolerant winter cereals was initiated at the International Center for Agricultural Research in the Dry Areas (ICARDA) in 1993. Here, I report the results obtained on the differential responses to high levels of soil B in the three crops. Seedlings of advanced lines and germplasm accessions were first screened in a plastic house in tanks of soils mixed evenly with known amount of boric acid. Then lines with low B-toxicity symptoms and B concentrations were grown in pots up to maturity. There was significant variation in seedling B-toxicity symptom scores and shoot B concentrations in all three crops at high soil B levels, with barley and bread wheat having larger variation than durum wheat. In a barley trial, most of the varieties from West Asia had low degrees of symptoms while the European varieties had high degrees of symptoms. This suggested that B is a factor causing European varieties to be poorly adapted to the region. In general, wheat had less symptoms than barley, and could grow in soils with a higher B level. Tolerant lines grew much more vigorously than sensitive lines under high soil B levels, resulting in large differential grain yield responses to increasing B levels between lines. On average, barley suffered more grain loss than durum, while bread wheat had the least yield reduction. The advantages of exploiting genetic tolerance over soil reclamation are presented. Growing varieties with high tolerance to B toxicity is the only practical approach to increase or maintain yields on inherently high-B soils, where there is no concern about further B build-up
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