Similarities and Variabilities in Ten Cassava Germplasms from International Institute of Tropical Agriculture Onne Rivers State Nigeria

Abstract

Cassava (Manihot esculenta Crantz.) is among the most important staple food crop in sub-Saharan Africa, consumed frequently by a population of more than 800 million people across this region (Lebot, 2009). Cassava is the third most important source of calories in the tropics (FAO, 2010) and the sixth most significant food crop after rice, maize, sugar cane, wheat and potato, in terms of global annual production (FAOSTAT, 2010). Cassava global annual production is approximately 291.9 million tons with Africa contributing more than 177 million tons, which is about 60.9% of global production (FAOSTAT, 2019). Added to this, Nigeria has the largest contribution to global productivity, with an annual production of about 59 million tonnes (FAOSTAT, 2019), more than Abstract: The quest to establish cassava cultivars with increased yield, pest and drought resistance has led to the establishment of several cassava germplasms but with little or no independent study on these germplasms. Hence, we employed basic morphological and anatomical protocol to ascertain the similarities and variabilities among 10 cassava germplasms and their potentials for yield, pest and drought resistance. Cassava germplasms were grown in soil-filled polypots, maintained at 50% field capacity and parameters like plant height, leaf area, petiole length, petiole insertion type, lobe margins, nature of cuticles, number of vasculatures in stems and petioles, presence/absence of trichomes in midribs and estimated area of vascular bundles were measured at 45 days after planting. Data collected were subjected to descriptive statistics and petiole insertion type, reticulate venation, lobe margin and number vasculatures in stems revealed similarities among all germplasms studied, thus indicating an identical ancestral origin. Nonetheless, variations were observed in plant height, leaf area, nature of cuticles, petiole length, number of vasculatures in petiole and presence/absence of trichomes in midrib. Germplasms like TMS 95/0289, TMS 95/0166, TMS 92/0057, TMS 91/02324 were among the top performing lines on plant height, petiole length, leaf area and number of vasculatures present in the petiole and Pearson coefficient correlation among these four parameters revealed a strong positive relationships statistically significant at p < 0.05, thus indicating that these germplasms will contribute to breeding of cassava cultivar with improved yield capabilities, as the selection of one of these parameters will positively influence others. Germplasms like TMS 96/0166, TMS 97/0211, TMS 9/1089A and TMS 98/2101 were top performers on qualities of drought and pest resistance via the presence of trichomes, thick leaf cuticles, reduced number of petiole vasculatures and area of vascular bundles in both petioles and midribs. Thus, our results suggest a possible tradeoff between breeding for increased yield and breeding for resistance to pest and drought but an exception was revealed in germplasm TMS 96/0166, which performed relatively well for increased yield potentials, drought and pest resistance. Thus, further studies are required to relate the data from studied juvenile cassava germplasms with that of their matured field grown counterpart. Also, there is need for the identification of quantitative trait loci and understanding of the genetic basis responsible for the traits revealed in germplasm TMS 96/0166 and the variabilities observed among other germplasms.