Genetic Modification and Application in Cassava, Sweetpotato and Yams

Cassava (Manihot esculenta Crantz), sweetpotato (Ipomoea batatas) and yams (Dioscorea spp.) are important root and tuber crops grown for food, feed and various industrial applications. However, their genetic gain potentials are limited by breeding and genetic bottlenecks for improvement of many desired traits. This book chapter covers the applications and potential benefits of genetic modification in breeding selected outcrossing root and tuber crops. It assesses how improvement of selected root and tuber crops through genetic modification overcomes both the high heterozygosity and serious trait separation that occurs in conventional breeding, and contributes to timely achievement of improved target traits. It also assesses the ways genetic modification improves genetic gain in the root and tuber breeding programs, conclusions and perspectives. Conscious use of complementary techniques such as genetic modification in the root and tuber breeding programs can increase the selection gain by reducing the long breeding cycle and cost, as well as reliable exploitation of the heritable variation in the desired direction.

​Quality Characters of Tannia [Xanthosoma sagittifolium (L.). Schott] as Affected by Tillage, Planting Methods, Plant Nutrition and Application of Soil Conditioners

Background: Tannia is one of the six most important root and tuber crops grown world-wide. Tannia possess good keeping quality compared to other vegetables. The tubers are considered more nutritious than colocasia and potato. But the crop is still under-exploited compared to other tuber crops. Hence the study was undertaken to identify the effect of tillage and nutrition on quality characters of tannia. Methods: A field experiment was conducted at College of Agriculture, Vellayani, Kerala during 2014-15 to study the effect of organic nutrition on quality characters of tannia. The design used was split plot design with four replications. The treatments consisted of tillage and planting methods as main plot treatments (L1- conventional tillage followed by pit system, L2- conventional tillage followed by mound system, L3- deep tillage followed by pit system and L4- deep tillage followed by mound system). The sub plot treatments were combinations of soil conditioners (S1- control, S2- coir pith, S3- rice husk) and two nutrition systems (N1- integrated nutrient management (INM) and N2- organic nutrition). Result: Results of the experiment revealed that the quality characters of tannia was improved by deep tillage to a depth of 30 cm followed by pit system of planting, application of coir pith as soil conditioner @ 500 g plant-1 and organic nutrition (FYM @37.5 t ha-1 + wood ash @ 2 t ha-1).

Employing CRISPR/Cas Technology for the Improvement of Potato and Other Tuber Crops

New breeding technologies have not only revolutionized biological science, but have also been employed to generate transgene-free products. Genome editing is a powerful technology that has been used to modify genomes of several important crops. This review describes the basic mechanisms, advantages and disadvantages of genome editing systems, such as ZFNs, TALENs, and CRISPR/Cas. Secondly, we summarize in detail all studies of the CRISPR/Cas system applied to potato and other tuber crops, such as sweet potato, cassava, yam, and carrot. Genes associated with self-incompatibility, abiotic-biotic resistance, nutrient–antinutrient content, and post-harvest factors targeted utilizing the CRISPR/Cas system are analyzed in this review. We hope that this review provides fundamental information that will be useful for future breeding of tuber crops to develop novel cultivars.