Selection of cassava (Manihot esculenta Crantz) parental lines for the development of varieties with high yield and resistant to major diseases

Cassava (Manihot esculenta Crantz) is a top crop commodity in developing countries. It ranks 3rd as the most important food crop next to rice and corn. There is wide diversity and distinctiveness among the heterozygous plants that can contribute to the upgrading of genetic resources for cassava varietal improvement programs. A total of 276 cassava accessions were collected from different provinces in the Philippines. These collected accessions were evaluated and characterized using morphological characters and molecular markers. An average of 0.76 Shannon-Weaver index obtained from the morphological data showed that the accessions are highly diverse. Molecular markers, on the other hand were used to screen the diversity of the collected accessions. At 0.48 similarity index, a total of 7 clusters were generated using the binary data from the SSR primers. Accessions that grouped in cluster 6 showed the highest average yield of 22.2 t/ha. Some of these markers can also be applied directly in the cassava breeding program since they are gene-specific markers for interesting traits. Gene-specific primers were also used to screen for CMV resistance, early bulking and cyanogenic potential. Based on the markers and yield parameters, 45 promising accessions were selected and 39 out the 45 showed resistance to CMD. These accessions also did not exhibit any symptoms, unlike the accessions planted in the border. Using the early bulking markers, 34 accessions showed positive results. However, only 5 accessions were able to exhibit positive results on the markers for a cyanogenic potential, which means that majority of the accessions are edible or with low cyanide. Unfortunately, markers for CaWB were not able to identify potentially resistant members of the collection. After determining the yield of the accessions, a total of 45 elite accessions were selected with high yield, high starch content, as well as CMV resistance, and early bulking traits. The selected superior lines would undergo hybridization to produce promising lines that can be released in the future as a commercial variety.