Assessment of yield components of some cassava (Manihot esculenta Crantz) genotypes using multivariate analysis such as path coefficients

Cassava, which is a tropical storage root crop, serves as a veritable source of carbohydrate for people living in Sub-Saharan Africa. It is also an important source of industrial starch, biopolymers, animal feeds and ethanol. However, the genetic improvement of the crop is impeded by dearth in information on its genetic variability. A field experiment was carried out at the National Root Crops Research Institute, Umudike (05° 29′ N; 07° 33′ E; 122 m a.s.l.), Nigeria, aimed at assessing the interrelationship between fresh root yield and thirteen quantitative yield-related characters of twenty-eight (28) newly developed cassava genotypes. The rain-fed experiment was laid out in a randomized complete block design with dual replications in 2016/2017 cropping seasons. The results indicated that the newly developed cassava genotypes [2] NR110315 followed by [20] B1-5 and [1] NR110238 exhibited (P < 0.05) highest fresh root yield among the twenty-eight genotypes tested. The fresh root yield of [2] NR110315 (18.77 Mt ha⁻¹) was relatively higher compared with [18] NR050080, which gave the least root yield of 5.38 Mt ha⁻¹. The correlation coefficients obtained from the associations among the variables were positive and exhibited highly significant (P ≤ 0.01) association, especially between leaf area index (LAI) and root diameter as well as with fresh root yield of cassava. Among the nine variables subjected to the path analysis, LAI, starch content, above ground dry matter (AGDM), weight of fresh marketable roots per plant and root length that contributed positively and directly to higher fresh root yield require greater attention during selection and breeding in cassava studies. The direct effect of the variables indicating their magnitudes in decreasing order showed that LAI exhibited the greatest effect followed by starch content, AGDM, weight of fresh marketable roots plant⁻¹, root length, % cassava bacterial blight incidence and % Cassava mosaic disease incidence, which had the lowest direct effect on root yield of cassava. Cyanide potential exhibited a direct, weak and negative effect on fresh root yield. The results further suggested that cassava improvement could be achieved through these characters that have positive and highly significant magnitude effect on fresh root yield.