No abstract

The use of plasticulture systems, which consist of raised beds, plastic mulch, and drip irrigation for watermelon production, has increased in the Southern United States in recent decades. The root-knot nematode (RKN), Meloidogyne incognita, is a significant pathogen of watermelon production in plasticulture systems and can cause varying levels of yield loss depending on the nematode population density if not properly controlled. Few new non-fumigant nematicides (fluensulfone, fluazaindolizine, and fluopyram) have emerged in the last decade to help manage RKNs. A two-year field study was conducted to examine the impact of different rates, application timing (i.e., days before transplanting [DBT], at transplanting [AT], and days after transplanting [DAT]), and combination of these new nematicides and an older one (oxamyl) in control of RKN in watermelon cv. ‘Fascination’. The nematicide treatments, except for a single-time application of oxamyl in 2019 and 2020, significantly reduced root galling compared to the untreated check. Similarly, all treatments, except a single application of oxamyl in 2020, resulted in a lower soil population level of M. incognita than the untreated check. All nematicide treatments, except a single application of fluensulfone and a two-time application of fluopyram at a half-recommended rate, increased fruit yields when compared to the untreated check. Overall, the drip application of new chemistries, known as 3-F nematicides, shows to be a useful option for RKN management in watermelon. At planting application of fluazaindolizine or fluopyram and two-time applications of oxamyl based on the manufacturer's recommended rate show potential to prevent the crop loss.

This study characterized, identified and conducted phylogenetic analysis on fungi contaminants in vitro bananas based on the sequence of inter-space (ITS) regions. Genomic DNA was extracted from the pure culture of fungi contaminants, amplified and sequenced using ITS1 and ITS4 markers. Analysis of the sequences using MEGA 7 Software at higher similarity sequence identified five Aspergillus spp., three Penicillium spp., one each of Fusarium, Trichoderma and Cladosporium as the contaminants. The genetic distance between the fungi species was 0.205, which suggests a homogeneous substitution between the sequences, and thiamine was the most stable. The fungi clustered in three major groups at 0.10 genetic distance, subdivided into five clusters. A cluster and sub-cluster consisting of five Aspergillus strains; a major cluster of three Penicillium strains; a cluster comprising of Fusarium chlamydosporum and Trichoderma viride; and a sole fungi Cladosporium tenuissimum. The Aspergillus group were phylogenetically related to A. flavus and A. parvissclerotigenus, the identified Penicillium spp. were closely related to Penicillium citrinum while the detected Cladosporium aligned with Cladosporium tenuissium and Phoma multirostrata. The information provided by this study could be utilized to develop a specific and compelling sterilization protocol to minimize the rate of contamination during in vitro culture procedures.