ABSTRACT
Groundnut (Arachis hypogaea Linn) is an important legume in western Kenya, but yields are
low and declining. Pests and diseases are ranked high among the yield reducing factors.
Groundnut rosette disease (GRD) is the main disease and can cause up to 100% yield loss.
Rosette is transmitted mainly by the groundnut aphid, Aphis craccivora Koch and to a lesser
extent by Aphis gosypii Glover and Myzus persicae Sulzer. Rosette is caused by two
synergistic viruses; groundnut rosette assistor virus (GRAV, genus Luteovirus) and
groundnut rosette virus (GRV, genus Umbravirus) associated with a satellite-ribonucleic acid
(sat-RNA). Inadequate current information on the occurrence, distribution and diversity of
GRAV causing GRD in western Kenya, is a limiting factor on proper diagnosis and
management of GRD which gave the impetus for this study. This study determined the
occurrence, distribution and diversity of GRAV on groundnuts in western Kenya. A survey of
GRD was conducted in Bungoma and Kakamega Counties during the short rains (October –
December 2016) and long rains (May – June 2017). Symptomatic leafy samples were
collected in falcon tubes containing RNALater solution, and preserved for laboratory
analysis. The data collected on incidence and severity was subjected to analysis of variance
and pairwise comparison of means done using Least Significance Difference at P ≤ 0.05.
Screening for resistance to GRAV was done on five popular legume varieties and one
solanaceous Physalis peruviana Linn. The plants at three leaf-stage were mechanically
inoculated with GRD inoculum prepared from leaves of RT-PCR positive samples. The
plants were monitored for symptom development in the screenhouse for 8 weeks. Total RNA
was extracted from the leaf samples using RNeasy Mini Kit (Qiagen) according to the
manufacturers’ protocol. The extracted total RNA was used for double stranded cDNA
synthesis using the SuperScript II kit. DNA libraries were prepared and sequenced on the
MiSeq platform (Illumina). Quality check on reads was done using FastQC. Trimmed reads
were used for de novo assembly and contigs aligned to the viral genomes database using CLC
Genomics Workbench 10.1.2. The assembled contigs were subjected to a BLASTn search
against the GenBank database. Phylogenetic analyses and comparisons were performed using
the MEGA X software. Primers used in RT-PCR were designed using Primer3Plus software
from consensus sequences. A total of 144 farms were surveyed. Rosette was observed in all
the surveyed areas with chlorotic symptoms being dominant followed by green rosette and
mosaic. Mean rosette incidence was higher in Bungoma (66.51%) than Kakamega (60.52%).
Short rains had higher mean incidence than the long rains season. Nucleotide sequences of
GRAV coat protein (CP) gene revealed 97-99% identity among the western Kenya isolates
and those from Ghana, Malawi and Nigeria. All tested plants developed viral symptoms and
tested positive for GRAV by RT-PCR. The fact that GRD occurs wherever groundnuts are
grown in western Kenya, is of great concern and may be the reason for the observed low
yields. Incorporation of GRD resistant genes in the local cultivars/varieties may be the only
practical solution.
Simiyu, A (2021). Occurrence, Distribution And Molecular Diversity Of Groundnut Rosette Assistor Virus Causing Groundnut Rosette Disease In Western Kenya. Afribary. Retrieved from https://afribary.com/works/occurrence-distribution-and-molecular-diversity-of-groundnut-rosette-assistor-virus-causing-groundnut-rosette-disease-in-western-kenya
Simiyu, Anthony "Occurrence, Distribution And Molecular Diversity Of Groundnut Rosette Assistor Virus Causing Groundnut Rosette Disease In Western Kenya" Afribary. Afribary, 08 May. 2021, https://afribary.com/works/occurrence-distribution-and-molecular-diversity-of-groundnut-rosette-assistor-virus-causing-groundnut-rosette-disease-in-western-kenya. Accessed 06 Nov. 2024.
Simiyu, Anthony . "Occurrence, Distribution And Molecular Diversity Of Groundnut Rosette Assistor Virus Causing Groundnut Rosette Disease In Western Kenya". Afribary, Afribary, 08 May. 2021. Web. 06 Nov. 2024. < https://afribary.com/works/occurrence-distribution-and-molecular-diversity-of-groundnut-rosette-assistor-virus-causing-groundnut-rosette-disease-in-western-kenya >.
Simiyu, Anthony . "Occurrence, Distribution And Molecular Diversity Of Groundnut Rosette Assistor Virus Causing Groundnut Rosette Disease In Western Kenya" Afribary (2021). Accessed November 06, 2024. https://afribary.com/works/occurrence-distribution-and-molecular-diversity-of-groundnut-rosette-assistor-virus-causing-groundnut-rosette-disease-in-western-kenya