| dc.description.abstract | In Kenya, rice is an important staple crop after wheat and maize and the rate of
consumption surpasses its production. Apart from consumption, rice is a cash crop for
smallholder farmers including those in Kirinyaga County. Despite its usefulness in
contributing to food security, rice production has remained low due to various
constraints. Among these are plant-parasitic nematodes (PPN) that account for up to
20% of yield losses. Other than the deleterious effect of PPN, rice agroecosystems
contain free living nematodes (FLN) that play important ecological roles such as
decomposition of organic matter and suppression of destructive PPN. However, through
various cropping practices, the diversity and structure of the nematode communities is
altered which affects crop productivity. This study examined the abundance and
additively partitioned diversity of nematode communitiesin rice in Mwea. Soil samples
were collected from 30 rice fields in Nyangati (15) and Tebere (15) in Mwea, Kirinyaga
county. Nematode extraction was done using the modified Baermann technique before
enumeration and identification to the genus level. To determine the differences in the
abundance of nematode genera, one-way analysis of variance (ANOVA) was used.
Spatial distribution of nematode communities in Nyangati and Tebere wasexamined
using Jaccard index-based non-metric multidimensional scaling.One-way ANOVA was
used to evaluate the differences in the indices and metabolic footprints in Nyangati and
Tebere. Gamma diversity was additively partitioned into α and β components in the R
package vegan.Turnover and nestedness components of beta diversity were computed
using the betapart package in R software. The relationship between soil properties and
nematode genera was evaluated using canonical correspondence analysis. There were 17
nematode genera in both regions with Aphelenchoides and Longidorus occurring in
greater proportions in Tebere.The population of Helicotylenchus was high in Nyangati
and Prodorylaimus occurred in high numbers in both regions.Aphelenchoides was
positively correlated to electrical conductivity while Helicotylenchus was negatively
correlated.The two regions could not be unequivocally ordered due to crossing of the
Renyi diversity profiles along the scale parameter.Genus richness partitioning, showed
that α and β components contributed 33.7% and 66.3% of the γ diversity,
respectively.Partitioning of beta diversity showed that nestedness contributed to the
overall nematode diversity observed in Nyangati and Tebere rice fields.Results obtained
from this study provide information that could aid in development and implementation
of effective and environmentally sound nematode management practices in rice. | en_US |
