Studies of pigeonpea insect pests and their management in Kenya, Malawi, Tanzania and Uganda

Systematic surveys were conducted in farmers= fields in Kenya, Malawi, Tanzania, and Uganda to determine the incidence, distribution and damage levels due to insect pests of pigeonpea seeds. Three surveys were conducted in eastern Kenya, one in 1992 and two in 1995. Two surveys, one per country per year - were conducted in Malawi, Tanzania, and Uganda in 1995 and 1996. Key insect pests were pod sucking bugs (dominated by Clavigralla tomentosicollis Stal), pod and seed boring Lepidoptera (Helicoverpa armigera Hübner, Maruca vitrata (= testulalis) Geyer, Etiella zinkenella Treitschke), and pod fly (Melanagromyza chalcosoma Spencer). Seed damage due to insect pests were 22, 15, 14, and 16% in Kenya, Malawi, Tanzania, and Uganda, respectively. Damage levels indicated that pod sucking bugs were more damaging in Malawi (caused 69% of total seed damage) and Kenya (43%), while pod borers caused more damage in Tanzania (50%) and Uganda (54%). Pod fly caused more damage in Kenya than in the other countries. Pod borer damage was high in early maturing crops and pod fly in late maturing crops, while pod sucking bugs damage was high regardless of crop maturity period. Greater variations in seed damage were observed between locations in Kenya, Malawi, and Tanzania than in Uganda. Warm and dry locations had less seed damage than warm and humid, cool and dry, or cool and humid locations in Kenya, Malawi and Tanzania. None of the farmers visited in Malawi, Tanzania, and Uganda used conventional pesticides on pigeonpea in the field. Over 80% of these farmers used traditional methods in storage pest management. In contrast, 35 and 53% of farmers in Kenya had used conventional pesticides on long-duration pigeonpea genotypes in their fields

Genic SNP markers and legume synteny reveal candidate genes underlying QTL for Macrophomina phaseolina resistance and maturity in cowpea [Vigna unguiculata (L) Walp.]

<p>Abstract</p> <p>Background</p> <p><it>Macrophomina phaseolina </it>is an emerging and devastating fungal pathogen that causes significant losses in crop production under high temperatures and drought stress. An increasing number of disease incidence reports highlight the wide prevalence of the pathogen around the world and its contribution toward crop yield suppression. In cowpea [<it>Vigna unguiculata </it>(L) Walp.], limited sources of low-level host resistance have been identified, the genetic basis of which is unknown. In this study we report on the identification of strong sources of host resistance to <it>M. phaseolina </it>and the genetic mapping of putative resistance loci on a cowpea genetic map comprised of gene-derived single nucleotide polymorphisms (SNPs) and amplified fragment length polymorphisms (AFLPs).</p> <p>Results</p> <p>Nine quantitative trait loci (QTLs), accounting for between 6.1 and 40.0% of the phenotypic variance (R²), were identified using plant mortality data taken over three years in field experiments and disease severity scores taken from two greenhouse experiments. Based on annotated genic SNPs as well as synteny with soybean (<it>Glycine max</it>) and <it>Medicago truncatula</it>, candidate resistance genes were found within mapped QTL intervals. QTL <it>Mac-2 </it>explained the largest percent R²and was identified in three field and one greenhouse experiments where the QTL peak co-located with a SNP marker derived from a pectin esterase inhibitor encoding gene. Maturity effects on the expression of resistance were indicated by the co-location of <it>Mac-6 </it>and <it>Mac-7 </it>QTLs with maturity-related senescence QTLs <it>Mat-2 </it>and <it>Mat-1</it>, respectively. Homologs of the <it>ELF4 </it>and <it>FLK </it>flowering genes were found in corresponding syntenic soybean regions. Only three <it>Macrophomina </it>resistance QTLs co-located with delayed drought-induced premature senescence QTLs previously mapped in the same population, suggesting that largely different genetic mechanisms mediate cowpea response to drought stress and <it>Macrophomina </it>infection.</p> <p>Conclusion</p> <p>Effective sources of host resistance were identified in this study. QTL mapping and synteny analysis identified genomic loci harboring resistance factors and revealed candidate genes with potential for further functional genomics analysis.</p

Multiple evolutionary origins of Trypanosoma evansi in Kenya

Trypanosoma evansi is the parasite causing surra, a form of trypanosomiasis in camels and other livestock, and a serious economic burden in Kenya and many other parts of the world. Trypanosoma evansi transmission can be sustained mechanically by tabanid and Stomoxys biting flies, whereas the closely related African trypanosomes T. brucei brucei and T. b. rhodesiense require cyclical development in tsetse flies (genus Glossina) for transmission. In this study, we investigated the evolutionary origins of T. evansi. We used 15 polymorphic microsatellites to quantify levels and patterns of genetic diversity among 41 T. evansi isolates and 66 isolates of T. b. brucei (n = 51) and T. b. rhodesiense (n = 15), including many from Kenya, a region where T. evansi may have evolved from T. brucei. We found that T. evansi strains belong to at least two distinct T. brucei genetic units and contain genetic diversity that is similar to that in T. brucei strains. Results indicated that the 41 T. evansi isolates originated from multiple T. brucei strains from different genetic backgrounds, implying independent origins of T. evansi from T. brucei strains. This surprising finding further suggested that the acquisition of the ability of T. evansi to be transmitted mechanically, and thus the ability to escape the obligate link with the African tsetse fly vector, has occurred repeatedly. These findings, if confirmed, have epidemiological implications, as T. brucei strains from different genetic backgrounds can become either causative agents of a dangerous, cosmopolitan livestock disease or of a lethal human disease, like for T. b. rhodesiense

Study of e+e−→ppˉe^+e^- \rightarrow p\bar{p} in the vicinity of ψ(3770)\psi(3770)

Using 2917 $\rm{pb}^{-1}$ of data accumulated at 3.773~$\rm{GeV}$, 44.5~$\rm{pb}^{-1}$ of data accumulated at 3.65~$\rm{GeV}$ and data accumulated during a $\psi(3770)$ line-shape scan with the BESIII detector, the reaction $e^+e^-\rightarrow p\bar{p}$ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of $e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}$, $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p})$, is found to have two solutions, determined to be ($0.059\pm0.032\pm0.012$) pb with the phase angle $\phi = (255.8\pm37.9\pm4.8)^\circ$ ($<$0.11 pb at the 90% confidence level), or $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}) = (2.57\pm0.12\pm0.12$) pb with $\phi = (266.9\pm6.1\pm0.9)^\circ$ both of which agree with a destructive interference. Using the obtained cross section of $\psi(3770)\rightarrow p\bar{p}$, the cross section of $p\bar{p}\rightarrow \psi(3770)$, which is useful information for the future PANDA experiment, is estimated to be either ($9.8\pm5.7$) nb ($<17.2$ nb at 90% C.L.) or $(425.6\pm42.9)$ nb

Colonisation of Cotesia flavpipes (Hymenoptera: braconidae) in stemborders in the semi-arid eastern province of Kenya

Field surveys carried out in Mozambique showed that two indigenous cereal stemborers, Busseola fusca Fuller (Lepidoptera: Noctuidae), Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and one exotic stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), are the main pests of maize and sorghum in the country. Busseola fusca was abundant at high altitudes (> 800 m) and Ch. partellus was abundant at low altitudes (< 800 m). Sesamia calamistis occurred at all elevations but in low numbers. Of the three stemborers, Ch. partellus was the most widespread and abundant pest of maize followed by B. fusca. Therefore, a programme was initiated to introduce the exotic parasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae) to increase natural suppression of Ch. partellus populations. Cotesia flavipes was introduced into southern Mozambique for the first time in November 1996. Additional releases were subsequently carried out in several places in southern and central Mozambique from 1998 - 2000. The parasitoid was recovered from all localities sampled 1 to 3 years after its introduction, indicating that this exotic parasitoid had established in the southern and central regions of Mozambique. RÉSUMÉ Durant quatre saisons (courtes saisons des pluies 1996 - longues saisons 1998), une étude a été menée à Katumani, Kiboko et Ithookwe dans la zone sémi-aride de la province de l'est du Kenya. Elle avait pour but de confirmer les principales espèces de foreur de tige de mais, d'introduire et de suivre la colonisation par Cotesia flavipes Cameron (Hymenoptera: Braconidae) de ces foreurs. Environ 6750 adultes de Cotesia flavipes ont été lâché à chaque site à partir d'une semaine après émergence des plantes et répété toutes les deux semaines jusqu'â la récolte. Le parasitisme avant les lâchés a été mesuré durant deux saisons. Le parasitisme a aussi été mesuré pendant la saison des lâchés et une saison après. La parasitisme a été évalué à partir des different stades de développement collectés après échantillonage destructif de 100 plantes à partir d'une semaine après la germination. Ceci a été répété toutes les semaines à Katumani et une fois toutes les deux semaines à Kiboko et Ithookwe, ceci jusqu'à la récolte. Les foreurs collectés sur du maïs étaient les suivants: Chilo partellus, Sesamia calamistis, Cryptophlebia leucotreta et Busseola fusca dans l'ordre descendant d'abondance avec Chilo partellus come étant l'espèce la plus répandue. Cotesia flavipes a parasité et colonisé avec success Ch. partellus et Sesamia calamistis dans les 3 sites pendant la saison des lâchés et une saison après lâchés. Le parasitisme par Co. flavipes était compris entre 7.14 et 25.80 %. La vitesse de colonisation des deux foreurs majeurs de la zone semi-aride de la province de l'est du Kenya est une indication du grand potentiel qu'aurait ce parasitoid à assurer la régulation de population des foreurs de tige de maïs dans cette région

Regional distribution of lepidopteran stemborers and their parasitoids among wild grasses in the semi-arid eastern Kenya

A survey was conducted in six agroecological zones (AEZs) in semi-arid eastern Kenya, in May, 1996, to identify the major wild host grasses (abundance ≥ 70%) for stemborers in each zone. The grasses sampled were Pennisetum purpureum   Schumach, P. trachyphyllum Pilg., Panicum maximum   Jacq, Sorghum versicolor   Anderss, Cenchrus ciliaris   L. and Cyperus   sp. Among these grasses, P. purpureumwas the most widespread and abundant. The survey was followed by an on-farm study conducted in each of the six AEZs to determine the relative abundance and distribution of stemborers, that infested the major wild grasses and their parasitoids . This was done by destructive sampling of 100 tillers, at a three-month interval, from July 1997 to April 1998. The stemborers that infested the grasses were Chilo partellus   Swinhoe and Sesamia calamistis   Hampson. Among these, C. partelluswas the predominant species, with the highest number being recovered on S. versicolor (94.6%). Parasitoids were only reared on S. versicolor, and these were Cotesia sesamiae   (Cameron), C. flavipes Cameron, Chelonus curvimaculatus   (Cameron), Pristomerus   sp. and Norbanus   sp., with C. flavipes causing the highest parasitism (13.6%). Results reveal that S. versicolor exhibited potential for use in the management of stemborers in maize, by acting as a "trap" and "refuge" crop for C. flavipes, between cropping seasons

Studies of pigeonpea insect pests and their management in farmers' fields in Kenya, Malawi, Tanzania, and Uganda

(African Crop Science Journal 1999 7(1): 59-70