Abstract
Cereal crop improvement programmes involve the analysis of a great number of lines every year; the availability of a simple, rapid method that would allow the identification of a trait in the early stages of plant development would facilitate the selection process. This work reports two experiments involving the germination of seeds in Petri dishes, performed to study the effect of water deficit on the growth of barley coleoptiles. In one experiment water stress was induced by allowing evaporation from the Petri dishes; in the other water stress was achieved by adding polyethylene glycol 6000. The growth of the control coleoptiles was greater than that of the treatment coleoptiles in all cases, but with differences between the different genotypes. A significant correlation (P < 0.01) was found between the relative growth of the coleoptiles and turgor maintenance in the seedlings. Significant correlations were also seen between the relative growth of the coleop-tiles and the osmotic adjustment of the flag leaf (P < 0.05) and the grain weight (P < 0.01) in adult plants. The genotypes that showed the greatest relative growth also showed the greatest capacity for osmotic adjustment in the flag leaf and produced the greatest yields in experiments with adult plants. The results indicate that the growth of coleoptiles subjected to water deficit could be used as a selection criterion in breeding programmes designed to improve the tolerance of barley to drought.
Highlights
Obtaining high, stable yields is a priority aim of cereal improvement programmes
A significant correlation was obtained between the relative growth of the coleoptiles and under evaporation-induced water deficit conditions (Figure 1)
When water deficit was induced with PEG, the correlation between osmotic adjustment and relative growth was significant (Table 4)
Summary
Stable yields is a priority aim of cereal improvement programmes. In environments affected by drought the improvement of yield is difficult given the low heritability of this trait and because of the variable quantity and temporal distribution of soil water. The use of secondary traits, including physiological traits [1], has been proposed as a possible solution to this problem In this approach the identification of traits that contribute towards drought tolerance and that can be used as selection criteria in improvement programmes is essential for increasing selection efficiency, especially in climates in which water availability is low. The majority of physiological traits associated with drought tolerance that could be used as selection criteria are not easy to measure, and physiological screening tests are complex and slow when a large number of genotypes are involved These problems can be minimised, if traits of interest can be measured in the first stages of development with plants growing in controlled environments as long as these measures are sufficiently closely correlated with drought tolerance at crop level. Heat-stress was associated with a decrease in the rate of growth and in the final length of barley and wheat coleoptiles [3,4]
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