Effects of water stress on growth and yield of spring wheat (Triticum o,estit)um L.) cultivars Y.A. Abayomil and D. Wright
Schoo/ ot' Agricultural snd Forest Science, Uniuersity College of North Wsles, Bangor Gwynedd, LL57 2 UW, United Kingdom
Two experiments were conducted to evaluate the effects of water stress applied at different growth stag€s, -on the growth, yield components, and grain yield of spring-wheat (Triticum aestiuum L.)- cultivars. The effects of watei stress on gro-wth aird yieU were smaller aird recov9W bettet when the stress was applied in the early vegetative phise than when applied in the late vegetatiye and p,ost-anthesis stages. Water stiess occurring in the early veg6t-ative phase -after decreased tiller production, but this was compensated by production of late tillers rewatering. A waler stress occurring during growth stages 32-65 days decreased spikelet fertil-reduction ity,and_ the number of grains per ear whicli was the greatest contiibutor to the in yield. Other components, however, such as number of-ears per unit area also contributed to -differences the- reduction- in yield._ There were highly significant genotypic in absolute grain yield and yield stability under water stress and awns appeared to be crucial in this respect. Overall, water stress had a greater effect on yield when it occurred during the reproductive stage and it is suggested that screening for water stress tolerant genotypes in cereals should be dbne at the reproductive etage-
Keywords, Water stress; Growth stages; Growth and yield; Spring wheat cultivars
Reports (Davidsonand Chevalier, 1987) have shown that the growth and yield of cereals are reduced by soil moisture deficits, and the extent to which yields are affected in cereal crops is dependent on the stage of development at which the deficits occur (Entz and Fowler, 1988). ln wheat, growth is affected by water stress which can reduce the final number of tillers per plant by reduced tiller production and (or) increasedtiller mortality (Fischer,I973). Davidson and Chevalier (1.987) reported that polyethyleneglycol (PEG)-induced water deficiis delayed tiller initiation, reduced leaf area production, dry matter accumulation,and the number of tertiary and quaternarytillers. The effects of water deficit on individual yield components and harvest index (HI) in wheat have also been shown to be dependent on the stage of growth at which stress occurs (Day and Intalap, 1970). The number of kernels per spike of wheat has been reported to be most severely reduced by water stress during ihe 15 days prior to anthesis (Baier and Robertson, 7969), and while water stress during grain filllng reduces kernel weight, yield decreasesfrom stress at this time are usually less severe than from stress just prior to anthesis (Musick and Dusek, 1980). Although drought is recognisedas an important limitation to cereal crop production, seleclPresent Address: Department of Crop Production, Universityof llorin, P.M.B. 1515, Ilorin, Kwara State, Nigeria
tion techniques have not been adequatelydeveloped (Schoifeld et al., 1988), which would limit breeding for drought resistance(Abd-Ellatif and Wiebel. 1,978\. There is therefore a need to better understand the mechanisms that enable the plant to adapt to water deficits and maintain growth, development,and productivity during stress periods, as this might help in breeding for drought resistance(Seropian and Planchion, 7984\. The aim of this study was, Iherefore, to measure the growth and yield responses of spring wheat cultivars to water stress, with a view to identifying the best that can be used as drought tolercharacter(s) ance indicator(s)and the best growth stage(s) (GS) for screening crop genotypes for drought tolerance.
Site description, experimentaldesign, and treatment application The study was carried out in unheated glasshouses at the college farm, University of Wales, Bangor Gwynedd, United...