Raghwendra Singh

Correspondence of ISSR and RAPD markers for comparative analysis of genetic diversity among different apricot genotypes from cold arid deserts of trans-Himalayas

The phylogenetic relationships of 36 locally grown Prunus armeniaca genotypes which are collected from nine sampling sites from two valleys viz. Nubra (9,600 ft) and Leh (11,500 ft) of trans-Himalayan region were analyzed using 31 PCR markers (20 RAPDs and 11 ISSRs). This is the first report of molecular genetic diversity studies in apricot from this region of the world. RAPD analysis yielded 139 fragments, of which 136 were polymorphic, with an average of 6.8 polymorphic fragments per primer. ISSR analysis produced 58 bands, of which 56 were polymorphic, with an average of 5.09 polymorphic fragments per primer. The primers based on (CT)n produced maximum number of bands (nine) while, (AT)n and many other motifs gave no amplification. RAPD markers were found more efficient with regards to polymorphism detection, as they detected 97.84 % as compared to 96.5 % for ISSR markers. Clustering of genotypes within groups was not similar when RAPD and ISSR derived dendrogram were compared, whereas the pattern of clustering of the genotypes remained more or less the same in RAPD and combined data of RAPD + ISSR. The results of PCA analysis were comparable to the cluster analysis. These analyses, allowed us to identify the groups corresponding to the two apricot collection sites.

Molecular Mapping of a Gene for Fertility Restoration of Wild Abortive (WA) Cytoplasmic Male Sterility using a Basmati Rice Restorer Line

The inheritance and molecular mapping of a fertility restorer gene in basmati quality restorer line PRR-78 was carried out using an F2 mapping population from the cross IR58025A X PRR-78 employing microsatellite markers. Dominant monogenic control of fertility restoration was observed in the F2, and further confirmed by test cross data. Out of 44 sequence tagged microsatellite (STMS) markers used in the bulked segregant analysis (BSA), four differentiated the fertile bulk from the sterile bulk as well as the two parental lines from each other. One of these markers, RM258 located on chromosome 10, was found linked to the restorer gene at a distance of9.5 cM. Considering the RM258 location, additional STMS (RM171 and RM294A) and sequence tagged site (STS) primers derived from restriction fragment length polymorphic (RFLP) clones (G2155 and C1361) linked to fertility restorer gene(s) in other populations, were also used to find out a marker more tightly linked to the restorer gene. However, of these, RM171, RM294A and G2155 based primers amplified monomorphic fragments between parental lines and no amplification was observed with C1361. Cleaved amplified polymorphic sequence (CAPS) analysis of non-polymorphic STMS and STS markers and random amplified polymorphic DNA (RAPD) analysis using five random primers reportedly linked to restorer gene in other populations, also failed to differentiate the two parents. While, the marker RM258 is being used in the restorer breeding to identify putative restorer lines, search for additional tightly linked markers is underway.

Weed Stress in Plants

Few plant species utilize available natural resources more efficiently as compared to other species in order to establish themselves in prevailing environmental conditions. Once established in early phase of growth, they can be sustained throughout the growing season by virtue of better stand. And this is the strategy behind the success of most of the notorious weeds in any cropping system. They, hence, continue to cause huge yield losses despite every effort made by farmers to manage them. Herbicides are largely used to manage weeds globally, but its application is also known to cause stress, though minimal, in crop plants. Another factor which contributes to the success of weeds is their hardiness and resilience to abiotic and biotic stress factors. Molecular mechanism(s) responsible for traits like competitiveness and invasiveness of weeds is poorly understood till date. However, development and availability of sophisticated molecular tools pave the way to dissect the mechanism of weed dominance. Competitiveness and tolerance to stress factors are important traits observed among different weed species that can be exploited in attempts to develop crop plants tolerant to abiotic/biotic stress(es). The need of the hour is to understand the molecular mechanisms underlying weed competitiveness over crop plants in field and to utilize the responsible gene(s) by transferring them into crop plants. However, success of such approaches depends upon integration and collaboration to bring expertise together from weed science, molecular biology, and plant physiology. An effort has been made to review the traits available among weed species that make them competitive and hardy.

Weed control in sesame with pre-emergence herbicides

Pendimethalin, imazethapyr, metribuzin, oxyfluorfen, imezemox were evaluated as pre-emergence herbicides in sesame during summer season of 2013 and 2014 at ICAR-Directorate of Weed Research, Jabalpur. All the herbicides reduced the weed population significantly as compared with weedy check but delayed the germination of sesame and caused sesame injury. Among all the herbicides, pendimethalin alone and in combination with lower dose of imazethapyr caused less injury to the sesame and produced higher sesame yield. None of the herbicides surpassed the yield what was achieved with 2 HW.

Identification of marker-trait associations for morphological descriptors and yield component traits in sugarcane

Ninety two sugarcane varieties from sub-tropical India were subjected to molecular profiling with 174 simple sequence repeat markers and characterized for 23 qualitative (morphological descriptors) and nine quantitative traits that directly or indirectly contribute to yield and juice quality. Using STRUCTURE-based population stratification study and a mixed linear model for marker-trait association (MTA) analysis, a total of 60 MTAs were identified for 22 qualitative traits that were able to explain a significantly higher (up to 40%) proportion of the phenotypic variations compared to all the previous reports of MTA studies in sugarcane. In addition, 21 MTAs stable over the three years of study were also identified for nine quantitative traits that explained 16–37% of the total trait variation. It could be concluded that the qualitative traits that are governed mostly by one or a few genes are more responsive to MTA studies and hence have a better potential to be adopted in marker-assisted breeding programmes in sugarcane. The MTAs identified in this study could also find significant applications in upcoming more stringent IP regime, which may necessitate tracking of specific alleles integrated in breeding programmes.

Fenoxaprop-p-ethyl effect against weeds in late sown wheat

Delayed sowing of wheat tends to reduce germination count and number of tillers/unit area because of sharp rise in temperature during tillering phase of the crop and ultimately decrease in yield (Soomro and Oad 2002). Hence, an attempt was made to cultivate weed free late sown wheat by use of fenoxaprop-p-ethyl at different doses in lieu of higher productivity and profitability from rice fallow areas.