EFFICACY OF BOTANICAL EXTRACTS FROM GARLIC AND NEEM ON CONTROLLING POTATO SOFT ROT PATHOGENS

Soft rot of potatoes (Solanum tuberosum L.) caused by Pectobacterium and Dickeya subspecies leads to economic losses in agriculture worldwide including Zimbabwe, where losses range from 20 – 60%. A laboratory experiment was carried out using the potato tuber maceration test to screen the effect of two botanicals extract, neem (Azadirachta indica A. Juss.) leaf and garlic (Allium sativum L.) cloves in controlling soft rot disease caused by bacterial pathogens, namely Pectobacterium carotovorum subspecies carotovorum (Pcc), Pectobacterium atrosepticum (Pa) and Dickeya dadantii (Dd). Preparations of two concentrations [(10 and 25% (w/v)] of the aqueous extracts of garlic and neem plants were used in dip and spray applications. Sterile distilled water was used as a negative control. Three tuber halves were used for each treatment. Five 10 mm filter paper discs (Whatman’s No. 1) pre-soaked in 1 x 106 cfu/mL bacterial cell suspensions of Pcc, Pa and Dd respectively were placed on each tuber half and incubated for 48 h at 25oC. After 48 h the filter paper discs were removed and the rotting zone diameter was measured. The experiment was a 3x2x2x2+1 factorial laid out in a completely randomised design, each treatment replicated three times. The two botanicals significantly inhibited the growth of two bacteria, Pa and Dd but were ineffective against Pcc. Concentration, method of application and their interactions were not significant in inhibiting the bacteria. Neem and garlic extracts can be used to control Pa and Dd infections

Effect of BAP, NAA and GA3, either alone or in combination, on meristem culture and plantlet establishment in sweet potato (cv Brondal)

In Zimbabwe, the average sweet potato yield (6 t/ha) is relatively low when compared to Asian counterparts (17 t/ha). These low crop yields have been blamed on weevil infestations and viral infections which account for 60-90% of sweet potato yield losses in Africa. Meristem tip culture, a Centre for Potato Improvement (CIP) initiated tissue culture technique, has been widely used to eradicate viruses from clonally propagated crops and has been noted to be one of the instrumental techniques that helped China to increase sweet potato yields. In an effort to adopt the meristem tip culture technique for the production of virus-free planting material of a local sweet potato (cv Brondal), a study was conducted to evaluate the effect of Benzylamino purine (BAP), 1-Naphthaleneacetic acid (NAA) and Gibberellic acid (GA3) (either alone or in combination) on cultured Brondal meristems. The different hormonal treatments were assessed on the following parameters: plantlet regenerative capacity, multiple plantlet production, shoot height, average leaf number per shoot and average node number per shoot, ten weeks after meristem culture. All treatments containing a combination of BAP (1 mg-L) and GA3 (at either 5 mg-L, 10 mg-L, or 20 mg-L) had a significantly (p<0.01) higher plantlet regenerative capacity of 33-66% when compared to other treatment combinations. Only treatments, 10 mg-L GA3 + 1 mg-L BAP and 20 mg-L GA3 + 1 mg-L BAP were capable of inducing multiple plantlet formation, producing an average of three plantlets/meristem and two plantlets/meristem respectively. Overall, treatment 10 mg-L GA3 + 1 mg-L BAP gave rise to significantly (p<0.01) taller shoots (20 mm) compared to the rest of the treatments used. For average leaf number per shoot, all GA3 treatments (5 mg-L, 10 mg-L, or 20 mg-L) supplemented with 1 mg-L BAP gave significantly (p<0.01) higher numbers of leaves (six leaves/shoot) than the rest of the treatments. Treatments 10 mg-L GA3 + 1 mg-L BAP and 20 mg-L GA3 + 1 mg-L BAP gave rise to the highest number of nodes per shoot, producing an average of three nodes per shoot. In sharp contrast to treatments containing a combination of BAP and GA3, all treatments containing a combination of BAP and NAA performed poorly in all parameters tested for plant regeneration of Brondal sweet potato variety. In conclusion, the best hormonal treatment for culturing Brondal meristems proved to be 10 mg-L GA3 + 1 mg-L BAP.Keywords: Ipomoea batatas, meristem, regeneration, Benzylamino purine, Gibberellic acid, 1-Naphthaleneacetic aci

Morphological and molecular characterisation of Streptomyces spp. which suppress pathogenic fungi

Streptomyces species are aerobes and chemoorganotrophic bacteria. These microorganisms produce a wide range of industrially significant compounds, specifically antibiotics and anti fungal substances. The objective of this study was to characterise soil-borne Streptomyces isolates using morphological and molecular traits in order to identify them to species level, and leverage from their potential to suppress the growth of Aspergillus flavus , Fusarium oxysporum and Penicillium italicum . Twenty-seven soil-borne putative Streptomyces, which elicited comprehensive\ua0antimicrobial activity against Aspergillus flavus, Fusarium oxysporum and Penicillium italicum, in a previous study, were evaluated. On the basis of morphology, the bacteria resembled the genus Streptomyces. Initially, colonies phenotypically appeared to have a relatively smooth surface but as growth progressed the bacteria developed a weft of aerial mycelium granular, powdery or velvety in appearance. Bacteria produced a wide variety of pigments which in turn were responsible for the colour of the vegetative and aerial mycelia, colour ranged from white to cream or buff shades and yellow to orange or brown. Microscopic analyses and morphological characteristics generated sub-groups of the isolates and clustered them according to their similarities. One bacterial strain was randomly selected from each cluster and investigated using molecular characteristics. Partial 16S rDNAs from the selected representative isolates from each subgroup, were sequenced and phylogenetic analysis performed. The 16S\ua0rDNA\ua0sequences of the isolates indicated that they were related to\ua0 Streptomyces species: S. bungoensis , S. thermocarboxydus , S. corchorusii and S. lasaliensis, that are known secondary metabolite producers possessing antimicrobial activity against plant pathogens.Les esp\ue8ces de Streptomyces sont des bact\ue9ries a\ue9robies et chimio-organotrophes. Ces micro-organismes produisent une large gamme de compos\ue9s d\u2019importance industrielle, en particulier des antibiotiques et des substances antifongiques. L\u2019objectif de cette \ue9tude \ue9tait de caract\ue9riser les isolats de Streptomyces transmis par le sol \ue0 l\u2019aide de traits morphologiques et mol\ue9culaires afin de les identifier au niveau de l\u2019esp\ue8ce, et de tirer parti de leur potentiel \ue0 supprimer la croissance d\u2019 Aspergillus flavus , Fusarium oxysporum et Penicillium italicum . Vingt-sept Streptomyces putatifs transmis par le sol, qui ont suscit\ue9 une activit\ue9 antimicrobienne compl\ue8te contre Aspergillus flavus, Fusarium oxysporum et Penicillium italicum, dans une \ue9tude pr\ue9c\ue9dente, ont \ue9t\ue9 \ue9valu\ue9s. Sur la base de la morphologie, les bact\ue9ries ressemblaient au genre Streptomyces. Au d\ue9part, les colonies semblaient ph\ue9notypiquement avoir une surface relativement lisse, mais au fur et \ue0 mesure que la croissance progressait, les bact\ue9ries d\ue9veloppaient une trame de myc\ue9lium a\ue9rien d\u2019aspect granuleux, poudreux ou velout\ue9. Les bact\ue9ries produisaient une grande vari\ue9t\ue9 de pigments qui \ue0 leur tour \ue9taient responsables de la couleur des myc\ue9liums v\ue9g\ue9tatifs et a\ue9riens, la couleur variait du blanc au cr\ue8me ou au chamois et du jaune \ue0 l\u2019orange ou au brun. Des analyses microscopiques et des caract\ue9ristiques morphologiques ont g\ue9n\ue9r\ue9 des sous-groupes d\u2019isolats et les ont regroup\ue9s en fonction de leurs similitudes. Une souche bact\ue9rienne a \ue9t\ue9 s\ue9lectionn\ue9e au hasard dans chaque groupe et \ue9tudi\ue9e en utilisant des caract\ue9ristiques mol\ue9culaires. Des ADNr 16S partiels provenant des isolats repr\ue9sentatifs s\ue9lectionn\ue9s de chaque sous-groupe ont \ue9t\ue9 s\ue9quenc\ue9s et une analyse phylog\ue9n\ue9tique a \ue9t\ue9 effectu\ue9e. Les s\ue9quences d\u2019ADNr 16S des isolats ont indiqu\ue9 qu\u2019ils \ue9taient apparent\ue9s aux esp\ue8ces de Streptomyces: S. bungoensis , S. thermocarboxydus , S. corchorusii et S. lasaliensis, qui sont des producteurs de m\ue9tabolites secondaires connus poss\ue9dant une activit\ue9 antimicrobienne contre les phytopathog\ue8nes

In vitro suppression of pathogenic fungi by Streptomyces spp.

The use of living organisms or natural enemies of pathogens to control their populations is called biological disease control. It involves harnessing and introduction of exotic species of microorganism in a natural form, with the intention of controlling pathogens that may exist naturally in the same ecosystem. Prospects for biological control of Aspergillus flavus , Fusarium oxysporum and Penicillium italicum were investigated using Streptomyces spp. isolated from Chinhoyi University of Technology Farm soils in Mashonaland West, Zimbabwe. Twenty seven Streptomyces spp were obtained from the soil, and screened for antimicrobial activity and antagonism in in vitro pathogen inhibition assays, replicated thrice. Although majority of the isolates tested elicited no effect on test pathogens, 22% of the Streptomyces isolates were able to effectively suppress A. flavus, F. oxysporum and P. italicum by at least 55%. There was a significant interaction between Streptomyces isolates and pathogen (A. flavus, F. oxysporum and P. italicum) (P<0.05) on fungal radial growth at days 7, 10 and 14 after pathogen-Streptomyces incubation. Antimicrobial potential against individual and multiple test pathogens was observed, with CUT-Streptomyces 4, CUT-Streptomyces 10, CUT-Streptomyces 11, CUT-Streptomyces 20 and CUT-Streptomyces 23 showing the greatest antimicrobial activity. CUT-Streptomyces isolates have the potential to suppress A. flavus, F. oxysporum and P. italicum in vitro.L\u2019utilisation d\u2019organismes vivants ou d\u2019ennemis naturels d\u2019agents pathog\ue8nes pour contr\uf4ler leurs populations est appel\ue9e contr\uf4le biologique des maladies. Il s\u2019agit d\u2019exploiter et d\u2019introduire des esp\ue8ces exotiques de microorganismes sous une forme naturelle, dans le but de contr\uf4ler les agents pathog\ue8nes pouvant exister naturellement dans le m\ueame \ue9cosyst\ue8me. Les perspectives de lutte biologique contre Aspergillus flavus , Fusarium oxysporum et Penicillium italicum ont \ue9t\ue9 \ue9tudi\ue9es \ue0 l\u2019aide de Streptomyces spp. isol\ue9es des sols agricoles de l\u2019Universit\ue9 de Technologie de Chinhoyi \ue0 Mashonaland West, Zimbabwe. Vingt-sept Streptomyces spp ont \ue9t\ue9 obtenus du sol et cribl\ue9s pour l\u2019activit\ue9 antimicrobienne et l\u2019antagonisme dans des tests d\u2019inhibition des agents pathog\ue8nes in vitro, r\ue9pliqu\ue9s trois fois. Bien que la majorit\ue9 des isolats test\ue9s ne provoquent aucun effet sur les agents pathog\ue8nes test\ue9s, 22% des isolats de Streptomyces sont capables de supprimer efficacement au moins 55% des A. flavus, F. oxysporum et P. italicum. Il y avait une interaction significative entre les isolats de Streptomyces et l\u2019agent pathog\ue8ne (A. flavus, F. oxysporum et P. italicum) (P< 0.05) lors de la croissance radiale des champignons aux 7\ue8me, 10\ue8me et 14\ue8me jours apr\ue8s l\u2019incubation de l\u2019agent pathog\ue8ne-Streptomyces. Un potentiel antimicrobien contre des agents pathog\ue8nes individuels et multiples a \ue9t\ue9 observ\ue9. CUT-Streptomyces 4, CUT-Streptomyces 10, CUT-Streptomyces 11, CUT-Streptomyces 20 et CUT-Streptomyces 23 ont montr\ue9 l\u2019activit\ue9 antimicrobienne la plus \ue9lev\ue9e. Les isolats de CUT-Streptomyces ont le potentiel de supprimer A. flavus, F. oxysporum et P. italicum in vitro

VARIABILITY IN CONDENSED TANNINS AND BITTERNESS IN SPIDER PLANT GENOTYPES

Spider plant ( Cleome gynandra L.) contributes considerably to the nutrition and medicines of communities in southern Africa. However, its utilisation is limited by its bitterness caused by condensed tannins. Unfortunately, processing options that reduce the bitterness also remove nutritionally and medicinally useful compounds. The objective of this study was to assess the genetic variability of condensed tannins and their association with bitterness in C. gynandra so as to devise variety recommendations for either direct utilisation or for breeding programmes in Zimbabwe. Total phenolic compounds and condensed tannins were quantified in five genotypes. The amount of total phenolic compounds were not significant, but quite significant (P<0.001) for condensed tannins. Genotype CGSKGP had the highest (0.49 mg g-1) and twice as much condensed tannins as CGKEX and CGSKP. Bitterness was positively correlated with the concentrations of condensed tannins (r=0.94, P<0.05), but not with total phenolics. We identified two genotypes, CGKEX and CGSKP with less bitterness (condensed tannins) that can be used in breeding for less bitterness to reduce excessive processing that lowers the nutritional and medicinal properties of C. gynandra.La plante araign\ue9e ( Cleome gynandra L.) contribue de fa\ue7on consid\ue9rable \ue0 la nutrition et \ue0 la m\ue9decine traditionnelle chez les communaut\ue9s en Afrique du Sud. N\ue9anmoins, son utilisation est limit\ue9e en raison de son go\ufbt amer caus\ue9 par la concentration en tanins. Malheureusement, le mode de transformation qui y r\ue9duit le go\ufbt amer r\ue9duit \ue9galement les nutriments et principes actifs utilis\ue9s en m\ue9decine traditionnelle. L\u2019objectif de cette \ue9tude \ue9tait d\ue9valuer la variabilit\ue9 g\ue9n\ue9tique du taux de tanins concentr\ue9 et la relation entre ce taux et le go\ufbt amer de C. gynandra, ceci pour recommander des vari\ue9t\ue9s appropri\ue9es soit pour l\u2019utilisation directe, soit pour des programmes d\u2019am\ue9lioration vari\ue9tales en Zimbabwe. Les taux globaux de compos\ue9s ph\ue9noliques et de tanins concentr\ue9s ont \ue9t\ue9 estim\ue9s dans cinq vari\ue9t\ue9s. L\u2019\ue9tude a montr\ue9 une diff\ue9rence significative pour les tanins concentr\ue9 (P<0.001), mais pas pour les compos\ue9s ph\ue9noliques. La vari\ue9t\ue9 CGSKGP avait la concentration la plus \ue9lev\ue9e (0.49 mg g-1) et \ue9tait deux fois plus concentr\ue9e en tanins que les vari\ue9t\ue9s CGKEX et CGSKP. Le gout amer \ue9tait positivement corr\ue9l\ue9 avec la concentration en tanins (r=0.94, P<0.05), mais pas avec les compos\ue9s ph\ue9noliques. Nous avons identifi\ue9s deux vari\ue9t\ue9s\ua0ayant un faible gout amer (tanins concentr\ue9s), CGKEX et CGSKP, qui peuvent \ueatre utilis\ue9es pour d\ue9velopper des vari\ue9t\ue9s am\ue9lior\ue9es ayant un faible gout amer afin de r\ue9duire les transformations excessives qui r\ue9duisent les propri\ue9t\ue9s nutritionnelles et m\ue9dicinales de C. gynandra

Effect of mixing cereal and legume straws on yield of grey oyster mushroom under controlled conditions

In Zimbabwe, yield of oyster mushroom ( Pleurotus ostreatus ) grown on sole substrates of maize or sorghum straw is low, <75% biological efficiency translating to less than a kilogramme of fresh mushroom per kg of dry substrate. This study aimed at determining the effect of mixing sorghum or maize straw with various proportions of bean straw, on the yield of grey oyster mushroom. Maize and sorghum straws were singly mixed with 0, 20, 40, 60, 80 and 100% bean straw, followed by a spawning rate of 5%. Eighteen days after incubation in a dark room, bags were hanged in a mushroom growing house with controlled temperatures (25-26oC). Mixing bean with maize straw had a significantly higher oyster mushroom yield (1, 229 g) than with sorghum straw (1,138 g); leading to biological efficiency of 83 and 74%, for maize straw and sorghum straw, respectively. Yield and biological efficiency decreased from 1,357 to 977 g plot-1 and 97 to 61%, respectively, when the proportion of bean straw was increased from 0-100%; while number of days to second and third harvest increased. There were significant interactions (P<0.05) for the number of pins, days to second and third harvest, between maize or sorghum straw with bean straw. Maize straw gave better performance with high percentages of bean straw than sorghum straw. Results showed that maize straw mixed with 20% bean straw produced better yield of grey oyster mushroom.Au Zimbabwe, le rendement de pleurotes ( Pleurotus ostreatus ) produites sur les substrats des pailles du ma\uefs ou du sorgho est faible, < 75% de l\u2019efficience biologique traduisant \ue0 moins d\u2019un kg des champignons frais par kg du poids sec du substrat. Cette \ue9tude visait \ue0 d\ue9terminerl\u2019effet du m\ue9lange des pailles du ma\uefs et du sorgho avec diverses proportions de la paille du haricot, sur le rendement du pleurote gris. Les pailles du ma\uefset du sorgho ont \ue9t\ue9 singuli\ue8rementm\ue9lang\ue9es avec 0, 20, 60, 80 et 100% de la paille du haricot, suivie par un taux de 5% de myc\ue9lium. Dix-huit jours apr\ue8s incubation dans une chambre noire, les sacs ont \ue9t\ue9 suspendus dans une chambre de croissance de champignon avec des temp\ue9ratures contr\uf4l\ue9es (25-26oC).Le m\ue9lange de la paille du haricot avec la paille du ma\uefs a eu un rendement significativement plus \ue9lev\ue9 du pleurote (1 229 g) qu\u2019avec la paille du sorgho (1 138 g)\ua0; entrainant une efficience biologique de 83 et 74%, pour la paille du ma\uefs et du sorgho, respectivement. Le rendement et l\u2019efficience biologique ont d\ue9cru du 1 357 \ue0 977 g plot-1 et 97 \ue0 61%,respectivement, quand la proportion de la paille du haricot a augment\ue9 de 0-100%\ua0; alors que le nombre de jours \ue0 la deuxi\ue8me et troisi\ue8me r\ue9colte a augment\ue9. Il y a eud\u2019interactions significatives (P<0.05) pour le nombre de broches, le nombre de jours \ue0 la deuxi\ue8me et troisi\ue8me r\ue9colte, entre la paille du ma\uefs etdu sorgho avec celle du haricot. La paille du ma\uefs a donn\ue9 de meilleures performances avec des pourcentages \ue9lev\ue9s de la paille du haricot que celle du sorgho. Les r\ue9sultats ont montr\ue9 que la paille du ma\uefs m\ue9lang\ue9e avec 20% de la paille du haricot ont produit de meilleur rendement du pleurote gris

Untapped potential of Livingstone potato, an indigenous and underutilised root crop in Zimbabwe: A review

The Livingstone potato ( Plectranthus esculentus ), a tuberous root vegetable indigenous to Africa, remains a neglected and underutilised crop species (NUCS). Of late, there has been a shift in how the NUCS are viewed as consumers become increasingly aware of their nutritional and medicinal value. The objective of the review was to highlight research developments of the Livingstone potato and to identify existing research gaps in a quest to unlock the potential of this crop. Traditionally, the vegetable has been utilised for food, economic and medicinal benefits. However, recent research developments in Africa have demonstrated that the Livingstone potato is highly nutritious and can provide raw materials for the agro and pharmaceutical sectors. While these are notable developments, more needs to be done, especially in Zimbabwe where there is very little researched information on its production and utilisation. The economic impact could potentially be at household, farmer and national level through establishing strong value chains. This is important in order to increase awareness and promote the crop, whose production is on the decline. The diversity and nutritional value of the Livingstone potato needs to be evaluated in Zimbabwe, as a step towards crop improvement, which is key to improved productivity. Continuous production at a large scale will help preserve the germplasm and prevent the genetic erosion currently taking place. This review echoes previous calls for the government of Zimbabwe to take bold steps to support the NUCS, such as the Livingstone potato, at policy level and to fund programmes that deal with such crops.La pomme de terre Livingstone ( Plectranthus esculentus ), un l\ue9gume-racine tub\ue9reux indig\ue8ne d\u2019Afrique, reste une esp\ue8ce qui est n\ue9glig\ue9e et qu\u2018 on la n\u2018 utilize pas. Ces derniers temps, I y a eu le changement pour la fa\ue7on de conciderer la pomme de terre Livingstone parceque les consommateurs deviennent de plus en plus conscients de leur valeur nutritionnelle et m\ue9dicinale. L\u2019objectif de la revue \ue9tait de mettre en \ue9vidence les d\ue9veloppements de la recherche sur la pomme de terre Livingstone et d\u2019identifier les lacunes de la recherche existante dans le but de decouvrir le potentiel de cette culture. Traditionnellement, le l\ue9gume a \ue9t\ue9 utilis\ue9 pour de ressources alimentaires, \ue9conomiques et m\ue9dicinales. Toutefois, des travaux de recherche r\ue9cents en Afrique ont montr\ue9 que la pomme de terre Livingstone \ue9tait tr\ue8s nutritive et pouvait fournir des mati\ue8res premi\ue8res aux secteurs agricoles et pharmaceutiques. Bien qu\u2019il s\u2019agisse d\u2019\ue9volutions notables, il reste encore beaucoup \ue0 faire, en particulier au Zimbabwe, o\uf9 tr\ue8s peu d\u2019informations ont \ue9t\ue9 recueillies sur sa production et son utilisation. L\u2019impact \ue9conomique pourrait potentiellement \ueatre au niveau des m\ue9nages, des agriculteurs et de pays. Ceci est important pour sensibiliser et promouvoir la culture, dont la production est en d\ue9clin. La diversit\ue9 et la valeur nutritionnelle de la pomme de terre Livingstone doivent \ueatre \ue9valu\ue9es au Zimbabwe, dans la perspective d\u2019une am\ue9lioration des cultures et essentiellement l\u2019am\ue9lioration de la productivit\ue9. Une continuite de la production \ue0 grande \ue9chelle aidera de pr\ue9server le germoplasme et de pr\ue9venir l\u2019\ue9rosion g\ue9n\ue9tique en cours. Cette revue fait \ue9cho aux appels precedents et au gouvernement du Zimbabwe pour prendre des mesures audacieuses et soutenir la pomme de terre Livingstone en financant des programmes qui font les recherches sul la pomme de terre Livingstone

Determining the pan-African sweetpotato virome: Understanding virus diversity, distribution and evolution and their impacts on sweetpotato production in Africa.

Food security remains a huge challenge for the millions of Africans dependent on agriculture for their subsistence. A low-level agricultural productivity and a high percentage of poor and undernourished people are common in Africa, particularly in sub-Saharan Africa (SSA). Sweetpotato, Jpomoea batatas (L.) Lam. (Family Convolvulaceae), is among the most important food crops in the world and an extremely important food crop for subsistence farmers in SSA. It is grown throughout the African continent and currently around 34.5% of global sweetpotato area is in Africa. SSA produces approximately 7 million tons of sweetpotato annually, only about 5% of global production. One major limitation in sweetpotato production is cultivar decline, mostly due to the cumulative effect of virus infection on this vegetatively propagated crop. Thus, viral diseases are nhbconsidered a major limiting factor in sweetpotato production woridwide, and particularly in SSA. However, there is a widespread lack of basic information and understanding of virus populations throughout Africa, even though such basic information is required to manage the spread and impact of these viral diseases. This project will focus on evaluating a novel approach, deep sequencing and assembly of small RNAs from field-grown sweetpotato samples collected throughout Africa, to systematically and efficiently identify virus genome. A Pan-African sweetpotato virome will be established, which will provide the scientific community and government unprecedented possibilities to understand sweetpotato virus distribution in Africa, guide phytosanitory requirements, predict risks of future epidemics, and suggest regional disease management strategies. In West-Africa the survey is expanded to include Cassava, Banana, Yams and Potato