The Arabidopsis thaliana WRKY proteins are characterized by a sequence of 60 amino acids including WRKY domain. It is well established that these proteins are involved in the regulation of various physiological programs unique to plants including pathogen defense, senescence and response to environmental stresses, which attracts attention of the scientific community as to how this family might have evolved. We tried to satisfy this curiosity and analyze reasons for duplications of these gene sequences leading to their diversified gene actions. The WRKY sequences available in Arabidopsis thaliana were used to evaluate selection pressure following duplication events. A phylogenetic tree was constructed and the WRKY family was divided into five sub-families. After that, tests were conducted to decide whether positive or purified selection played key role in these events. Our results suggest that purifying selection played major role during the evolution of this family. Some amino acid changes were also detected in specific branches of phylogeny suggesting that relaxed constraints might also have contributed to functional divergence among sub-families. Sites relaxed from purifying selection were identified and mapped onto the structural and functional regions of the WRKY1 protein. These analyses will enhance our understanding of the precise role played by natural selection to create functional diversity in WRKY family.
Tomato is a premier vegetable crop of round the year and one of the prominent eco-industrial crops of India generating sizeable employment. The present study which consisted 10 genotypes was evaluated in randomized block design replicated thrice at Regional Agricultural Research Station-Ujjain during Rabi 2007 to 2008. The variation was maximum (424 to 825 qtl/ha) for fruit yield and minimum for fruit width (4.1 to 5.6 cm). The magnitude of genotypic and phenotypic coefficient of variation was higher for number of leaves (21.2 and 22.3), fruit length (cm) (19.6 and 19.7) and fruit yield (19.6 and 19.6). High values of heritability coupled with high genetic advance were observed for number of leaves at 60 days after transplanting (99.4 and 64.9), and fruit yield (99.9 and 24.7). A positive association of yield per hectare observed with number of leaves at 60 days after transplanting (0.78) followed by number of leaves at 30 days after transplanting (0.68), fruit length (0.66) and plant height (0.51).
Late blight is the most devastating disease of the potato crop that can be effectively managed by growing resistant cultivars. Introgression of resistance (R) genes/quantitative trait loci (QTLs) from the Solanum germplasm into common potato is one of the plausible approaches to breed resistant cultivars. Although the conventional method of breeding will continue to play a primary role in potato improvement, molecular marker technology is becoming one of its integral components. To achieve rapid success, from the past to recent years, several R genes/QTLs that originated from wild/cultivated Solanum species were mapped on the potato genome and a few genes were cloned using molecular approaches. As a result, molecular markers closely linked to resistance genes or QTLs offer a quicker potato breeding option through marker-assisted selection (MAS). However, limited progress has been achieved so far through MAS in potato breeding. In near future, new resistance genes/QTLs are expected to be discovered from wild Solanum gene pools and linked molecular markers would be available for MAS. This article presents an update on the development of molecular markers linked to late blight resistance genes or QTLs by utilization of Solanum species for MAS in potato.Key words: late blight -molecular marker -MAS -potato -resistance gene -Solanum species Late blight caused by the oomycete (Phytophthora infestans (Mont.) de Bary) is the most important disease of potato production worldwide. This disease caused devastating impact on humanity in the mid-1840s when severe epidemics swept through Europe and resulted in the Irish potato famine (Fry 2008). Consequently, given its significant importance, there have been concerted global efforts for more than 100 years to develop durable resistant potato cultivars against P. infestans. However, evolution of new races of P. infestans was able to conquer the past resistance genes and resulted in susceptible cultivars worldwide. Durably resistant cultivars against a range of P. infestans isolates possessing multiple resistance genes are needed today, which can be developed in less time by conventional and molecular approaches. Regardless of the fact that common potato lacks significant sources of resistance, many wild Solanum species are rich sources of resistance genes. Globally breeders exploited only a very limited scale of Solanum biodiversity in potato breeding. For example, the genetic base of modern Indian potato cultivars is limited to 49 ancestors only involving the wild species S. rybinii and S. demissum. Late blight resistance genes were introgressed from the wild species S. demissum, S. stoloniferum and the cultivated S. tuberosum subsp. andigena and S. phureja into common potato in different parts of the world (Bradshaw et al. 2006c). Thus, it necessitates potato breeders to search for new sources of resistance in wild gene pools and their faster deployment into cultivars through markerassisted selection (MAS).Conventional breeding methods are of primary importance but ar...
Estimated breeding values using best linear unbiased prediction (BLUP) through pedigree relationship can enhance selection efficiency and save time as well as resources in autotetraploid potato breeding program. Here, we used historical preliminary yield evaluation trials data of 469–619 breeding lines for tuber yield and late blight resistance to estimate heritability and BLUP based breeding values modelling auto-tetraploid inheritance in mixed model analysis. The pedigree file had a depth of 3–4 generations with total 370 individuals including 111 founders. Heritability estimates varied from 0.15 for marketable tuber yield to 0.47 for late blight resistance computed using A matrix. The prediction accuracy for total tuber yield, marketable tuber yield and late blight resistance (AUDPC) was 0.53 ± 0.02, 0.44 ± 0.02 and 0.81 ± 0.01, respectively. The prediction accuracy was highest for late blight resistance and moderate for total and marketable tuber yield. The prediction bias measured as regression of observed phenotype values on predicted values for late blight resistance was almost nil in comparison to total and marketable tuber yield. Moderate to high prediction accuracies for tuber yields and late blight resistance suggest the selection of genotypes based on EBVs in Indian potato breeding programme for higher genetic gain.
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