PJB-2008-162
RELATIONSHIPS BETWEEN CARBON ISOTOPE DISCRIMINATION AND GRAIN YIELD, WATER-USE EFFICIENCY AND GROWTH PARAMETERS IN WHEAT (TRITICUM AESTIVUM L.) UNDER DIFFERENT WATER REGIMES
JAVED AKHTER , S. ALI SABIR, ZAHID LATEEF1 M. YASEEN ASHRAF AND M. AHSANUL HAQ
Abstract
The present studies were conducted to identify high yielding wheat genotypes for target environments and establish relationship between carbon isotope discrimination (Δ), grain yield (GY) and water use efficiency (WUE), and other parameters. A set of eight wheat genotypes screened previously for variation in Δ and higher GY were grown under four water regimes; well-watered (WW), medium-watered (MW), low-watered (LW) and stored soil moisture (SSM) conditions. Early leaf and grain samples collected at maturity were analysed for Δ. Plant parameters, such as number of tillers (NT), plant height (PH) heading days (HD), and maturity days (MD) were recorded. At harvesting spike length (SL), number of grains per spike (NGPS), thousand grains weight (TGW), biomass yield (BY), GY, harvest index (HI) and WUE on biomass basis (WUEB) and grain basis (WUEG) were determined. Significant effects of genotype and treatments on Δ of leaf (L) and grain (ΔG), BY, GY, HI, WUEB, WUEG, HD, NT, PH, NGPS, TGW and SL were observed. Genotype x treatment interaction had a significant effect on HI, PH, SL, TGW, HD and MD, but the effect was non-significant on other traits. In all these genotypes L and ΔG showed a variation of 1.3 and 0.91‰, respectively. All genotypes exhibited higher L than ΔG under different water regimes. Water stress reduced both L and ΔG and highly significant correlation (0.946**) was found between L and ΔG. GY showed a wide variation among these genotypes and water stress resulted in a marked decrease in GY. Genotype Sitta produced highest mean GY (4.4 Mg ha-1) with highest WUEG (16.99 kg ha-1 mm-1) averaged across the treatment. GY showed significant positive correlations with L (r=0.779*) and ΔG (r=0.753*). GY was also strongly and positively correlated with HI (r=0.845**), SL (r=0.779**) and TGW (r=0.899**). GY had a significant negative correlation with NT (r=-0.884*) and HD (r=-0.708*). WUEG was positively correlated with L (r=0.846*), ΔG (0.707*), HI (r=0.846**), SL (r= 0.784*), TGW (r=0.892**). WUEG was negatively correlated with NT (r=-0.814*) and HD (r= -0.743*). Sitta and FD-83 genotypes were found high yielder with greater increase in WUE under water stress and can be exploited to obtain high GY in rain-fed and water limited environments of the country. The results highlight significant positive correlations between Δ and GY or WUEG in bread wheat and carbon isotope discrimination as indirect selection criterion for grain yield in Pakistan.
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