Selection and testing of promising cassava varieties KM568, KM539, KM537 in Phu Yen province

Researching and breeding cassava varieties with high starch yield, resistance to major pests and diseases, and suitability to the production conditions of Phu Yen province and ecological regions is important and urgent. The objectives of this study were to select and create cassava varieties with high starch yield (at least 10% higher than controls KM419 and KM94), resistance to major pests and diseases, grade 1 - 2 disease scores for cassava mosaic disease (CMD), and cassava witches broom disease (CWBD). The research method was used according to Vietnam Cassava Program and International Center for Tropical Agriculture (CIAT) standards for technological process of hybrid cassava selection and breeding. The results showed that three promising cassava varieties KM568, KM539, and KM537 were identified. KM568, a hybrid of KM440 x (KM419 x KM539), yielded 54 tons/ha of fresh tubers with a starch content of 28.4% at harvest after 10 months of planting. KM539, a C39* variety, was developed from the original C39 variety from CIAT and yielded 45.9 tons/ha of fresh tubers with a starch content of 27.9%. KM537, a hybrid of (KM419 x KM539) x KM440, yielded 51.3 tons/ha of fresh tubers with a starch content of 28.5%. These three cassava varieties were resistant to CMD level 1.5 and CWBD level 1. KM568, KM539, and KM537 had 8 - 14 tubers/root, 7 - 12 tubers/root, and 7 - 12 tubers/root, respectively. Also, they all achieved the ideal new plant type shape, white root flesh, straight and compact plants, erect stems, short internodes, and less branching. Additionally, the plant height of KM568, KM539, and KM537 was 2.3 - 2.7 m, 2.7 - 3.0 m, and 2.5 - 2.9 m respectively.