Jaya R. Soneji

Characterization of zygotic and nucellar seedlings from sour orange-like citrus rootstock candidates using RAPD and EST-SSR markers

A series of crosses designed for introgression of mandarin (Citrus reticulata Blanco) and pummelo (C. maxima Merr.) germplasm, to develop an alternative rootstock to sour orange (C. aurantium L.), were carried out. It is necessary to identify those hybrids that yield nucellar seedlings for rootstock propagation. Rootstocks can be developed through traditional plant breeding methods; however, the ability to screen and select for economically important traits (such as production of true nucellar seedlings) in an efficient fashion is limited by the difficulties of screening techniques based on whole plant performance. To address these problems, we have used randomly amplified polymorphic DNA (RAPD) and fluorescently labeled expressed sequence tag simple sequence repeat (EST-SSR) molecular markers. A total of 204 individual seedlings obtained from 34 hybrid parental plants were successfully characterized using five RAPD primers. Ten hybrid parents and their progenies, found to be genetically similar among themselves, were selected for more scrutiny using eight EST-SSR primer pairs. The degrees of genetic similarity (nucellars) among progeny seedlings were determined and compared with that of their parents. The mean genetic similarity varied from 67–99% among the selected rootstock candidates screened. The genetic similarity relationship identified using RAPD and EST-SSR molecular markers was highly concordant (p = 0.001). Two elite rootstock candidates (B6R5T56; B6R11T129) that seem to be ideal for future mandarin and pummelo derived rootstock breeding programs have been identified. Our results indicate that either RAPD or EST-SSR analyses could be equally successful in identifying true nucellars among the progenies obtained from introgression crosses of mandarin and pummelo, thus improving the accuracy of early selection in a citrus rootstock breeding program.

Structure, Diversity, Threats and Conservation of Tropical Forests

In this elegant book, we have defined ‘Tropical Forests’ broadly, into five different themes: (1) tropical forest structure, synergy, synthesis, (2) tropical forest fragmentation, (3) impact of anthropogenic pressure, (4) Geographic Information System and remote sensing, and (5) tropical forest protection and process. The cutting-edge synthesis, detailed current reviews, several original data-rich case studies, recent experiments/experiences from leading scientists across the world (Fig.1) are presented as unique chapters. Though, the chapters differ noticeably in the geographic focus, diverse ecosystems, time and approach, they share these five important themes and help in understanding, educating, and creating awareness on the role of ‘Tropical Forests’ on the diversity of biota, impact of disturbances, climate change and the very survival of mankind.