Suppression of Stem-End Rot on Avocado Fruit Using Trichoderma spp. in the Central Highlands of Kenya

Demand for organic avocado fruits, together with stringent food safety standards in the global market, has made producers to use alternative, safe, and consumer-friendly strategies of controlling the postharvest fungal disease of avocado fruits. This study assessed the in vitro efficacy of Trichoderma spp. (T. atroviride, T. virens, T. asperellum, and T. harzianum) against isolated avocado stem-end rot (SER) fungal pathogens (Lasiodiplodia theobromae, Neofusicoccum parvum, Nectria pseudotrichia, and Fusarium solani) using a dual culture technique. The Trichoderma spp. were also evaluated singly on postharvest “Hass” avocado fruits. Spore suspension at 5 × 104 conidial/ml of the Trichoderma spp. was applied on the avocado fruits at three time points, twenty-four hours before the fungal pathogen (preinoculation), at the same time as the fungal pathogen (concurrent inoculation), and 24 hours after the fungal pathogen (postinoculation). In the in vitro study, T. atroviride showed the highest mycelial growth inhibition against N. parvum (48%), N. pseudotrichia (55%), and F. solani (32.95%), while T. harzianum had the highest mycelial growth inhibition against L. theobromae. Trichoderma asperellum was the least effective in inhibiting the mycelial growth of all the pathogens. Similarly, T. virens showed the highest mycelial growth inhibition against N. pseudotrichia at 45% inhibition. On postharvest “Hass” fruits, T. atroviride showed the highest efficacy against N. parvum, N. pseudotrichia, and F. solani in all the applications. Trichoderma virens and T. harzianum were most effective against all the pathogens during postinoculation, while Lasiodiplodia theobromae was best controlled by T. virens, T. harzianum, and T. asperellum during postinoculation. Both T. atroviride and T. harzianum present a potential alternative to synthetic fungicides against postharvest diseases of avocado fruits, and further tests under field conditions to be done to validate their efficacy. The possibility of using Trichoderma spp. in the management of SER on avocado fruits at a commercial level should also be explored

Identification and Pathogenicity of Fungal Pathogens Associated with Stem End Rots of Avocado Fruits in Kenya

Losses associated with stem end rot (SER) of avocado fruits have been reported in all avocado growing regions of the world. In Kenya, mature avocado fruits present SER symptoms during storage and marketing, but the disease causal agent(s) has not been established. This study aimed to identify the fungal pathogen(s) associated with avocado SER in Kenya and evaluate its pathogenicity. Fungal isolates were collected from symptomatic avocado fruits from randomly selected orchards and major markets within Murang'a County, a major avocado growing region in Kenya, between September 2017 and March 2018. A total of 207 and 125 fungal isolates, recovered from orchards and major markets, respectively, were identified morphologically and further confirmed by molecular techniques. The identified isolates were Lasiodiplodia theobromae (39.8%), Neofusicoccum parvum (24.4%), Nectria pseudotrichia (18.4%), Fusarium solani (7.2%), F. oxysporum (5.1%), F. equiseti (3.9%), and Geotricum candidum (1.2%). Geotricum candidum was exclusively recovered from fruits from the market. In the pathogenicity test, L. theobromae, N. parvum, and N. pseudotrichia caused the most severe SER symptoms. Consequently, they were considered to be the major pathogens of SER of avocado fruits in Kenya. To our knowledge, this is the first report of SER pathogen of avocado fruits in Kenya. Given the significant contribution of avocado fruits to household income and foreign exchange in Kenya, this information is significant to further develop management strategies of postharvest loss of avocado fruits in Kenya

Zeldia spannata sp. n. (Nematoda: Cephalobidae) from the Mojave Desert, California

Zeldia spannata sp. n. is described from the Mojave Desert, California. The new species shares with congeners a single guard process in each primary axil and asymmetrical triangular-shaped lips; it differs from them by the presence of elongate spanner-shaped, deeply bifurcate probolae (vs typically low, rounded and bicornuate). In addition, the new species has five lateral incisures (vs three in most other species of the genus), areolated lateral fields and tessellate cuticle (vs non-tessellate). Unlike some other Zeldia this new species lacks punctations. With respect to the bifurcate probolae, Z.spannata sp. n. resembles Chiloplacus or Stegelleta. Although the new species is reminiscent of some Nothacrobeles with respect to overall asymmetry, triangular shape of the lips, and the presence of tines on lips, maximum parsimony and maximum likelihood analyses of the ITS1, 5.8S and ITS2 of rRNA gene fragments from 13 taxa do not allow resolution of relationships between Zeldia species and several other cephalobid clades. The morphological characters of the new species are the basis for a broader, emended definition of the genus Zeldia, and suggest novel implications for evolution of Cephalobidae.Se describe Zeldia spannata sp. n. del desierto de Mojave, California. La nueva especie comparte con sus congéneres un único proceso guarda en cada axila primaria, así como los  labios asimétricos y triangulares; pero difiere de ellas en la presencia de probolas con forma de llave inglesa alargada y provistas de profundas bifurcaciones, en tanto que en las otras especies de Zeldia las probolas son típicamente bajas, redondeadas y bicorneadas. Además, Z. spannata sp. n. tiene cinco incisuras laterales (vs tres en la mayor parte de las otras especies), campos laterales areolados, y cutícula teselada (vs no teselada). A diferencia de algunas otras especies del género, la nueva especie carece de líneas de puntos. En lo que se refiere a la presencia de probolas bifurcadas, se asemeja a Chiloplacus o Stegelleta. Aunque la nueva especie es reminiscente de algunas pertenecientes al género Nothacrobeles si atendemos a la simetría general, la forma triangular de los labios y la presencia de púas en los mismos, los análisis de parsimonia máxima y probabilidad máxima de los fragmentos ITS1, 5.8S y ITS2 de rRNA de 13 táxones no permiten resolver las relaciones de parentesco entre especies de Zeldia y otros varios clados de cefalóbidos. Los rasgos morfológicos de la nueva especie son la base para una diagnosis corregida y más amplia del género Zeldia, al tiempo que sugieren implicaciones novedosas para la evolución de familia Cephalobidae