Synthesis and fungicidal activity of novel 4,4'-bis(2' '-aryl-5' '-methyl/unsubstituted-4' '-oxo-thiazolidin-3' '-yl) bibenzyl

Reduction followed by nitration of benzil I yielded 4,4'-dinitrobibenzyl (III) which by reduction furnished quantitatively and analytically pure 4,4'-diaminobibenzyl (IV) which on condensation with different carbonyl compounds gave 4,4'-bis (benzylideneamino) bibenzyls (Va-f). Compounds (Va-f) on cycloaddition with mercaptoacetic acid/2-mercaptopropionic acid yielded the corresponding 4-oxothiazolidin-3-yl bibenzyls (VIa-l). The compounds VIg-l have two chiral centers in each thiazolidinone moiety so two diastereomers are possible, but on crystallization and repeated chromatography, one diastereomer was obtained. The absolute configuration of the diastereomer was tentatively assigned on the basis of (1)H NMR spectra. (1)H NMR spectra of the product showed a distinct doublet at delta 1.22 for C(5)-CH(3) of thiazolidinone ring (22, 23) and a distinct quartet at delta 4.20 for the C(5)-H proton. Similarly, the C(2) proton showed an independent singlet at delta 5.95, so the diastereomers obtained were assigned trans configuration. Compounds Va-f and VIa-l were evaluated in vitro for their fungitoxicities against Fusarium oxysporium and Penicillium citrinum. All the compounds were found to be antifungal active. Some of the compounds displayed activities comparable with that of the commercial fungicide Dithane M-45. Structure-activity relationships for the screened compounds are discussed.     

Modeling yield sustainability for different rotations in long-term barley trials

In crop rotation trials, the errors arising over time on the same plot are correlated. Often-used analyses assume zero or constant correlation between the errors while the actual covariance structure for the plot errors might be very different. The objective of this study was to identify the most suitable covariance structure and incorporate the error structure in assessment of the crop rotations in terms of yield productivity and yield sustainability. A set of five covariance structures were examined for barley yield data from a 14-year, two-course barley rotation trial conducted at two locations in northern Syria. Selection of the covariance structures was based on the Akaike information criterion (AIC, Akaike 1974) (a function of penalized log-likelihood) obtained from fitting the structure. Covariance structure with heterogeneous variances and with constant correlation between errors over cycles within the same plot was found to account for most variability in grain and straw yields at both locations. Modeling data with this covariance structure, the legume rotations gave higher productivity as well as higher annual increases compared with the continuous barley system. This implies that an agricultural production system based on a legume following a cereal is likely to be more sustainable for cereal production compared to cereal followed by cereals.     

Validation of Molecular Markers and Haplotype Diversity at the SalTol Locus on Chromosome 1 of Rice

Rice （Oryza sativa L.） is the most important economic activity on earth as it is second largest single use of the land for food production and also consumed by the half of the world＇s population. Salinity is the one of the most common abiotic problem in rice growing areas of the world. Millions of hectares in the tropics, arid and semi arid region could be potential rice growing areas but either left idle or cropped with very low yielding varieties due to the lack of suitable salt tolerant high yielding modem varieties.     

Helminthosporium leaf blight resistance and agronomic performance of wheat genotypes across warm regions of South Asia

Helminthosporium leaf blight (HLB) is the most important disease constraint to wheat (Triticum aestivum L.) cultivation in the eastern Gangetic Plains of South Asia. A Helminthosporium Monitoring Nursery (HMN) including potential adapted and exotic sources of HLB resistance was developed in Bangladesh, India and Nepal to assess the stability of genetic resistance across locations. The 8th, 9th and 10th HMN assessed the HLB resistance and agronomic traits of 17 wheat genotypes across 20 environments of Bangladesh, India and Nepal in the 1999‐2000, 2000‐2001 and 2001‐2002 cropping seasons, respectively. The area under the disease progress curve (AUDPC) for HLB, grain yield, thousand‐kernel weight (TKW), days to heading, days to maturity, and plant height were examined. The 17 genotypes showed a range of variability for disease and agronomic characters. Disease severity (AUDPC) differed in the 3 years and showed the highest values in 2002. The increase in AUDPC in 2002 caused the lowest grain yield, with an average 18% reduction due to HLB. A few genotypes (SW 89‐5422, Yangmai‐6 and Ning 8201) appeared to have stable HLB resistance across environments. However, most of the higher‐yielding genotypes, except BL 1883, were unstable. The results suggest that careful selection of HLB resistance with acceptable grain yield, TKW and plant height may be possible using the wheat genotypes included in the HMN.     

Monosomic analysis of Helminthosporium leaf blight resistance genes in wheat

A set of 21 monosomic (2n ‐ 1) and the disomic (2n) lines of the ‘Chinese Spring’ cultivar were crossed with ‘Chirya‐3′, the CIMMYT synthetic wheat line which has been identified as highly resistant for Helminthosporium leaf blight disease (HLB), in order to locate the genes governing disease resistance. The F₁ and segregating populations were challenged and screened against the most virulent pure mono‐conidial HLB isolate KL‐8 (Karnal, India). The F₁ progenies of the crosses were found to be susceptible because of the recessive nature of resistance. The F₂ progeny of the control cross (‘Chinese Spring’בChirya‐3’), segregated in the ratio of 1: 15 (resistant: susceptible), indicating that resistance to HLB was controlled by a pair of recessive genes. While the F₂ progeny of 19 monosomic crosses segregated in the ratio of 1: 15 (resistant: susceptible), the progeny of the remaining two crosses, 7B and 7D, deviated significantly from the ratio, revealing that 7B and 7D were the critical chromosomes for resistance genes that were located one on each chromosome. Moreover, the critical lines, 7B and 7D, confirmed the digenic complementary recessive nature of gene action by fitting well with the overall pooled F₂ segregation ratio of 13: 51 (resistant: susceptible) as expected for digenic complementary recessive resistance. The F₃ segregation ratios of the critical crosses, based on their pooled F₂ analysis, was estimated as 19: 32: 13 (non‐segregating susceptible: segregating as susceptible and resistant: non‐segregating resistant). F₃ progenies when tested with these ratios showed goodness‐of‐fit, confirming that the two pairs of recessive resistance genes were located on chromosomes 7B and 7D.     

Identification of QTLs for BYDV tolerance in bread wheat

We searched for QTLs involved in tolerance to barley yellow dwarf (BYD), a serious viral disease of small grain cereals in two wheat populations, Opata × Synthetic (ITMI)and Frontana × INIA66 (F × I), for which marker data had previously been generated. The populations were evaluated in replicated field trials under artificial inoculation with a BYDV-PAV-Mex isolate and under disease-free conditions. Disease symptoms (yellowing, dwarfism and biomass reduction) were visually recorded and agronomic traits (number of tillers,height, biomass, yield and thousand-kernel weight) were measured on five plants per plot. Phenotypic data on all evaluated traits showed normal distribution with high correlation between visual estimates and measured values. Heritabilities were mostly moderate to high in the 114 lines of the ITMI population, and from low to moderate in the 117 lines of the F × I population. QTL analyses were based on genetic maps containing 443 loci for the ITMI population and 317 loci for the F × I population. Using composite interval mapping, 22 QTLs in the ITMI population and seven in the F × I population were detected, explaining9.8–43.3% of total phenotypic variation (σ² _P)per agronomic trait in the first population, and 4.1–13.7% in the second. Individual QTLs explained less than 15.8%of σ² _P. In the F × I population a minor QTL explaining 7% of σ² _P for yellowing was detected on the short arm of 7D, linked to leaf tip necrosis, a morphological marker for linked genes Bdv1, Yr18 andLr34. A QTL consistently detected for several traits on 2D in the ITMI population and on the short arm of group 6 chromosome(6S) in F × I explained 10–15% of σ² _P. The large number of QTLs having mostly small effects and the continuous distribution of all evaluated traits confirmed the polygenic nature and complexity of BYD tolerance in wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Resistance to stripe rust in Triticum turgidum,T. tauschii and their synthetic hexaploids

Resistance to stripe rust (caused by Puccinia striiformis Westend.) of 34 Triticum turgidum L. var.durum, 278 T. tauschii, and 267 synthetic hexaploid wheats (T. turgidum x T. tauschii) was evaluated at the seedling stage in the greenhouse and at the adult-plant stage at two field locations. Mexican pathotype 14E14 was used in all studies. Seedling resistance, expressed as low infection type, was present in all three species. One hundred and twenty-eight (46%) accessions of T. tauschii, 8 (23%) of T. turgidum and 31 (12%) of synthetic hexaploid wheats were highly resistant as seedlings. In the field tests, resistance was evaluated by estimating area under disease progress curve (AUDPC). Synthetic hexaploid wheats showed a wide range of variability for disease responses in both greenhouse and field tests, indicating the presence of a number of genes for resistance. In general, genotypes with seedling resistance were also found to be resistant as adult plants. Genotypes, which were susceptible or intermediate as seedlings but resistant as adult plants, were present in both T. turgidum and the synthetic hexaploids. Resistances from either T. turgidum or T. tauschii or both were identified in the synthetic hexaploids in this study. These new sources of resistance could be incorporated into cultivated hexaploid wheats to increase the existing gene pool of resistance to stripe rust.