The investigation was concerned with the effects of water stress on the yield and yield components of wheat grown under rainfed conditions in Rawalakot, Pakistan. A pot experiment was conducted with four wheat genotypes, Inqlab-91, Chakwal-97, Rawal-87 and Kohsar-95, tested against five irrigation levels with drought imposed at different growth stages including control, terminal drought, post-anthesis drought, three irrigations and pre-anthesis drought. The parameters studied were flag leaf area, ear stalk length, number of grains per spike and grain yield per pot. Flag leaf area and ear stalk length exhibited a significant reduction of 14 and 36%, respectively, when wheat was subjected to water stress. The proportional reduction in yield was 40% with three irrigations and 98% in the case of pre-anthesis drought depending upon the extent and degree of stress. Results showed that wheat could withstand and tolerate drought only up to anthesis, after which water stress resulted in the complete failure of the crop. It could be deduced that the critical stage for moisture in wheat started 60 days after germination, and became more severe at 90 days, i.e. at the anthesis stage. Among the genotypes, Inqlab-91 was found to be more tolerant of drought and could thus be a good option for further testing and recommendation for rainfed areas.
Authors:M. Sajjad, S.H. Khan, M.Q. Ahmad, A. Rasheed, A. Mujeeb-Kazi and I.A. Khan
A panel of 94 diverse hexaploid wheat accessions was used to map quantitative trait loci (QTL) underlying the yield related traits on chromosome 3A. Population structure and kinships were estimated using unlinked SSR markers from all 21 chromosomes. Analysis of variance revealed significant difference among accessions; however, genotype × year interaction was non-significant for majority of yield related traits. A mixed linear model (MLM) approach identified six QTLs for four traits that individually accounted for 10.7 to 17.3% phenotypic variability. All QTLs were consistently observed for both study years. New putative QTLs for the maximum fertile florets per spike and spike length were identified. This report on QTLs for yield related traits on chromosome 3A will extend the existing knowledge and may prove useful in marker-assisted selection (MAS) for development of high yielding cultivars.
Authors:M. W. Abbasi, M. Q. Khan, M. J. Zaki, S. S. Shaukat, A. Rauf, N. Ahmed, M. Azeem and M. Tariq
Bacillus thuringiensis (B.t) is well known for its biocontrol potential against a variety of insects. Nematicidal potential of ten B.t isolates was tested against root-knot nematodes (Meloidogyne javanica (Treub) Chitwood) in vitro, under greenhouse as well as in field conditions. Eggs and second stage juveniles (J2) were exposed to 5 and 25% concentrations of bacterial cell-free aqueous extracts up to 96 h. B.t isolates showed lesser degrees of nematicidal activity at 5% concentration. However, some B.t isolates (B.t-14, B.t-16 and B.t-64) greatly reduced egg hatching and increased J2. All B.t isolates revealed suppressed egg hatching and increased mortality of J2 at 25% concentration. Soil applications with most of the B.t isolates under greenhouse and field conditions significantly improved height and fresh weights of root-knot nematode parasitized okra (Abelmoschus esculentus (L.) Moench). Some isolates, including B.t-64 reduced the number of galls and egg masses. B.t-64 reduced gall formation up to 70% under greenhouse conditions. However, 29% of decrease was observed in field conditions. Similarly, B.t-64 treated plants showed a 56% decreased in eggs/egg mass in a field experiment. Population of root-knot nematodes in the rhizosphere was decreased up to 61% in the field experiment as compared to control.