Incidence of cassava mosaic disease and associated whitefly vectors in South West and North Central Nigeria: Data exploration

Cassava mosaic disease (CMD) is one of the most economically important viral diseases of cassava, an important staple food for over 800 million people in the tropics. Although several Cassava mosaic virus species associated with CMD have been isolated and characterized over the years, several new super virulent strains of these viruses have evolved due to genetic recombination between diverse species. In this data article, field survey data collected from 184 cassava farms in 12 South Western and North Central States of Nigeria in 2015 are presented and extensively explored. In each State, one cassava farm was randomly selected as the first farm and subsequent farms were selected at 10 km intervals, except in locations were cassava farms are sporadically located. In each selected farm, 30 cassava plants were sampled along two diagonals and all selected plant was scored for the presence or absence of CMD symptoms. Cassava mosaic disease incidence and associated whitefly vectors in South West and North Central Nigeria are explored using relevant descriptive statistics, box plots, bar charts, line graphs, and pie charts. In addition, correlation analysis, Analysis of Variance (ANOVA), and multiple comparison post-hoc tests are performed to understand the relationship between the numbers of whiteflies counted, uninfected farms, infected farms, and the mean of symptom severity in and across the States under investigation. The data exploration provided in this data article is considered adequate for objective assessment of the incidence and symptom severity of cassava mosaic disease and associated whitefly vectors in farmers’ fields in these parts of Nigeria where cassava is heavily cultivated.


a b s t r a c t
Cassava mosaic disease (CMD) is one of the most economically important viral diseases of cassava, an important staple food for over 800 million people in the tropics. Although several Cassava mosaic virus species associated with CMD have been isolated and characterized over the years, several new super virulent strains of these viruses have evolved due to genetic recombination between diverse species. In this data article, field survey data collected from 184 cassava farms in 12 South Western and North Central States of Nigeria in 2015 are presented and extensively explored. In each State, one cassava farm was randomly selected as the first farm and subsequent farms were selected at 10 km intervals, except in locations were cassava farms are sporadically located. In each selected farm, 30 cassava plants were sampled along two diagonals and all selected plant was scored for the presence or absence of CMD symptoms. Cassava mosaic disease incidence and associated whitefly vectors in South West and North Central Nigeria are explored using relevant descriptive statistics, box plots, bar charts, line graphs, and pie charts. In addition, correlation analysis, Analysis of Variance (ANOVA), and multiple comparison post-hoc tests are performed to understand the relationship between the numbers of whiteflies counted, uninfected farms, infected farms, and the mean of symptom severity in and across the States under investigation. The data exploration provided in this data article is considered adequate for objective assessment of the incidence and symptom severity of cassava mosaic disease and associated whitefly vectors in farmers' fields in these parts of Nigeria where cassava is heavily cultivated.  In addition to its significance as source of food and animal feed, cassava is increasingly becoming an important raw material for several industries including biofuel producing industries [1,2]. Therefore, addressing the incidence of cassava mosaic disease and associated whitefly vectors is considered pivotal to the realization of the Sustainable Development Goals (SDGs) numbers 1-3 (i.e. no poverty, zero hunger, and good health and well-being) by 2030 [3,4].
Nigeria is the highest producer of cassava globally and the plant is heavily cultivated in the South Western and North Central States of Nigeria [5,6]. The data provided in this data article will help in tackling the challenges of cassava mosaic disease and associated whitefly vectors in South West and North Central Nigeria. This solution will help the country to harness the potentials of cassava as an important source of foreign exchange.
The data exploration and the statistical analyses provided in this data article are considered adequate for objective assessment of the incidence and symptom severity of cassava mosaic disease and associated whitefly vectors in farmers' fields in these parts of Nigeria where cassava is heavily cultivated [7][8][9].
The data presented in this article will encourage reproducible research and open new doors of research collaborations towards finding effective solutions to deal with the evolution of new super virulent strains of cassava mosaic viruses.

Data
Cassava is a major staple food for millions of people in Nigeria and Africa at large. The plant is drought tolerant, grows in all agro-ecological zones in Nigeria and is one of the highest producing crops in terms of carbohydrate produced per hectare [10]. Beyond its use for food and animal feed, cassava is increasingly becoming a crucial raw material for several industries including biofuel producing industries. Cassava therefore has the potentials to become an important source of foreign exchange for Nigeria which is the highest producer of cassava globally [11]. This important plant is however plagued by several viral diseases which threaten its production and productivity. Cassava mosaic disease (CMD), one of the most economically important cassava virus disease, is wide spread in all areas where cassava is grown [12]. The virus is either seed  transmitted or transmitted by whitefly vectors [13]. A diversity of cassava mosaic virus species associated with CMD have been isolated and characterized over the years. However, several new super virulent strains of these viruses have evolved over the years due to genetic recombination between diverse species [14]. This data article seeks to evaluate the incidence and symptom severity of cassava mosaic disease and associated whitefly vectors in farmers' fields in South West and North Central Nigeria where cassava is heavily cultivated.

Experimental design, materials and methods
Cassava farms located along major and intermediate roads in all the State in the South West and North Central Nigeria were surveyed. The distribution of 184 cassava farms surveyed in 12 South Western and North Central States of Nigeria in 2015 is shown in Fig. 1. In each State, one cassava farm was randomly selected as the first farm and subsequent farms were selected at 10 km intervals except in locations were cassava farms are sporadically located. In each selected farm, 30 cassava plants were sampled along two diagonals and all selected plant was scored for the presence or absence of cassava mosaic disease (CMD) symptoms. Where present, CMD symptom severity was then scored on a scale of 2-5, with 2 indicating mild symptom and 5 indicating very severe symptom covering over 75% of the infected plant. A score of 1 was assigned for none symptomatic plants. The whiteflies present in the top five leaves if each sampled plant were also counted and recorded, to determine the abundance of these CMD vector across the States.  Tables 1-4 present the descriptive statistics (mean, median, mode, standard deviation, variance                  Correlation analysis, ANOVA, and multiple comparison post-hoc tests were performed to understand the relationship between the numbers of whiteflies counted, uninfected cassava plants, infected cassava plants, and the mean of symptom severity in and across the States under investigation. Correlation coefficient matrix and the p-value computed using the field data are presented in Table 5 and Table 6 respectively. Tables 7-14 give the results of the ANOVA and multiple comparison post-hoc tests for whiteflies counted, uninfected cassava farms, infected cassava farms, and mean of symptom severity across the 12 States of Nigeria. Figs. 19-22 show the mean comparisons of the four parameters for easy data interpretations.