DEVELOPING SUPERIOR CASSAVA [MANIHOT ESCULENTA (CRANTZ)] VARIETIES USING PARTIAL INBREDS - ABSTRACT
Studies were carried out to identify farmers’ preferences for cassava varieties and desired traits in Edo State. A pre-visit was made to the federal and state ministry of agriculture and to the local community heads to get the primary information. Focus group discussions were conducted followed by the administration of a Semi-Structured Questionnaire. The PRA was conducted in the three senatorial Zones of Edo State, a major cassava producing state in Nigeria. Two sets of elite S2 cassava lines were collected from National Root Crop Research Institute Umudike (NRCRI) and International Institute of Tropical Agriculture (IITA). The survey revealed that farmers in Edo State desire varieties with high yield, high dry matter, and starch content. It also revealed that the farmers prefer their local varieties to improved varieties. Two sets of crosses were made between the S2 lines. The first involved random matings and was done at the off season in November, 2012. The other was a 6x6 diallel mating design done in September, 2013 to determine combining ability, degree of heterosis and gene action influencing the yield and yield component traits. Much of the genetic variation identified among the S2 lines s was non-additive in nature. High heritability in some of the traits indicated high breeding value in the S2 lines. Sufficient useful genetic variation was present in the lines that could be exploited for high fresh root yield and dry matter. There was significant heterosis for yield and dry matter contents. For the first group of crosses, the highest mid-parent and better parent heterosis for root number was recorded in the hybrids TMS14-001-03 with 147% increase and TMS14-091-08 with 122.% increase. For fresh root yield, the highest positive mid-parent and better parent heterosis were recorded for the same hybrid TMS14-001-07 with 350.08% for MPH and with 276% for iv
BPH. The best MPH for dry matter content was recorded for the hybrid TMS14-035-5 with 18.3% and the same hybrid for BPH with 13.24%. For harvest index, the best hybrids for MPH was TMS14 091-04, with 39.2% and TMS14-035-06 with 33.9% increase respectively Eight hybrids recorded superior dry matter content and two hybrids recorded superior fresh root yield compared to the parents and checks. For the second group, ten hybrids had high fresh root yield, three hybrids had high dry matter, and seven hybrids had high total carotene content making a total of 20 superior hybrids. Significant heterosis was observed. The highest MP and BP heterosis for fresh root yield was seen in the cross IBA102888 X NRIS2109-10. The highest for BP heterosis for DM was seen in the cross IBA102923 X NRIS2109-14 .MP heterosis was as high as 204.68%, 63.98% and 89.77%, and BP heterosis was as high as 176.50%, 51.31% and 75.32% for the three traits, respectively. Five hybrids had high levels of heterosis and specific combining ability better than the best parent and the best check (farmers’ variety) used in the study.