Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 2.32

PHYSIOLOGICAL TRAITS AND ISOTOPIC DISCRIMINATION IN BARLEY GENOTYPES CONTRASTING FOR YIELD UNDER DROUGHT

F. RIZZA*, J. GHASHGHAIE**, C. LELARGE***, L. CATTIVELLI*, N. DI FONZO****, A.M. STANCA*

*) Istituto Sperimentale Cerealicoltura, Via S. Protaso 302, 29017 Fiorenzuola d’Arda (PC)

**) Laboratoire d’ Ecophysiologie Végétale, Bât 362, Univ. Paris Sud F-91405 Cedex, France

***) Laboratoire de Métabolisme et Structure des Plantes, IBP Univ. Paris Sud F-91405 Cedex, France

****) Istituto Sperimentale Cerealicoltura, SS 16 Km 675, 71100 Foggia

barley, drought, yield potential, yield stability, delta¹³C

The physiological, morphological and developmental traits contributing to drought resistance are either constitutive or induced or in some cases a combination of the two.

In this work 12 barley genotypes (6 six-rowed type and 6 two-rowed type) contrasting for yield potential and yield stability were selected on the basis of field data recorded during three years (from 1999 to 2001) at Foggia (South Italy), where about 100 genotypes of different origin, year of release, rows type and growth habit were evaluated in rainfed (R) and irrigated trials (I). The mean rainfall was 440 mm, 220 mm of which were received during the barley growing season.

The response of a given genotype in R and I trials was compared for yield and associated traits. Positive, highly significant correlations were found for all traits analysed in field (plant height, heading date, grain yield, kernel number m^-2, kernel weight. High yield in both R and I trials was achieved by the most productive genotypes throughout different stategies, probably associated with genotypic traits (higher kernel weight or higher kernel number, reduced plant height, early heading) and conserved under the range of water availability that occurred in the trials.

The 12 selected genotypes were further analysed for carbon isotopic composition (delta¹³C) of the grains harvested in the last season. The ¹³C discrimination, as a measure of the integrated WUE during the kernel development (Farquahar and Richards, 1984), was higher in the I trials for all tested genotypes. Higher discrimination is sustained by a higher ratio of intercellular to external partial pressure of CO₂ during photosynthesis, due to a higher stomatal conductance. Differences among genotypes for delta¹³C were significant within both R and I trials. The correlation between delta¹³C and yield was significant when analysed across treatments, but not within treatments. Apparently the stomatal conductance is not a trait that individually controls yield. Indeed, the two genotypes with the lowest and the highest delta¹³C belong both to the group of the low yielding genotypes. As shown for the other traits, also for the delta¹³C of the grains the response of the genotypes was conserved in R and I trials.

The overall data are consistent with the hypothesis that selection under favourable conditions allows to identify genotypes adpted to environments subjected to mild drought because the same mechanisms which operate under favourable conditions seem to work even at the levels of water limitation that occurred in our trials

References

Farquahar G.D. and R.A. Richards, 1984. Aust. J. Plant Physiol. 11: 539-552.