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The quantitative trait loci QYr.sun-3BS and QYr.sun-4DL were identified in the W195/BTSS recombinant inbred line (RIL) population in a previous study. QYr.sun-3BS explained 34 to 59% phenotypic variation in stripe rust response. We evaluated parental genotypes at different growth stages and temperature regimes to detect the critical stage for expression of QYr.sun-3BS. W195 expressed low infection type (IT) ;1C at the fourth leaf stage, when incubated at 21 ± 2°C and the alternate parent BTSS was susceptible (IT 3). Monogenic segregation for stripe rust response was observed among the RIL population at the fourth leaf stage and the underlying locus was temporarily named YrW195. YrW195 corresponded to QYr.sun-3BS. Since no previously designated stripe rust resistance genes that expresses at and after the fourth leaf stage was mapped in this region, YrW195 was formally named Yr58. Genotyping with Yr46-linked markers indicated the presence of Yr46 in W195, which corresponded to QYr.sun-4DL. The RILs carrying Yr58 and Yr46 singly produced IT 23C and IT 3, respectively, and those carrying both genes produced IT ;1C indicating the enhancement of Yr58 expression by Yr46. The absence of Yr58-linked alleles of markers sun533 and sun476 in 74 of the 76 wheat cultivars demonstrated their usefulness for marker-assisted selection.

Among the rust diseases, leaf rust of wheat caused by Puccinia triticina, is the most prevalent worldwide and causes significant yield losses. This study aimed to determine the genomic location of loci that control adult plant resistance (APR) to leaf rust in the pre-Green Revolution landrace accession, Aus27506, from the “Watkins Collection”. An Aus27506/Aus27229-derived F7 recombinant inbred line (RIL) population was screened under field conditions across three cropping seasons and genotyped with the iSelect 90K Infinium SNP bead chip array. One quantitative trait loci (QTL) on each of the chromosomes 1BL, 2B and 2DL explained most of the leaf rust response variation in the RIL population, and these were named QLr.sun-1BL, QLr.sun-2B and QLr.sun-2DL, respectively. QLr.sun-1BL and QLr.sun-2DL were contributed by Aus27506. QLr.sun-1BL is likely Lr46, while QLr.sun-2DL appeared to be a new APR locus. The alternate parent, Aus27229, carried the putatively new APR locus QLr.sun-2B. The comparison of average severities among RILs carrying these QTL in different combinations indicated that QLr.sun-2B does not interact with either of the other two QTL; however, the combination of QLr.sun-1BL and QLr.sun-2DL reduced disease severity significantly. In planta fungal quantification assays validated these results. The RILs carrying QLr.sun-1BL and QLr.sun-2DL did not differ significantly from the parent Aus27506 in terms of resistance. Aus27506 can be used as a source of adult plant leaf rust resistance in breeding programs.

Papaya (Carica papaya L.) is an economically important orchard crop, mainly cultivated in tropical and sub-tropical countries. Due its excellent medicinal value, papaw is recommended for daily consumption by medical professionals as fresh fruit. Papaya production is being hampered by papaya Anthracnose disease, caused by Colletotrichum gloeosporioides, which is inflicting major economic losses of around 40–100% during field cultivation, transportation, and storage in organic agriculture. An investigation was planned to assess the antifungal capacity of the medicinal plants Spinacia oleracea, Limonia acidissima, Allium sativum, Achyranthes aspera, Calotropis gigantea, Ocimum basilicum, Mukia scabrella, Ficus racemose, Azadiracta indica, Ocimum tenuiflorum, Lantana camara and Ocimum cinnamon combined with bee wax coating against papaya anthracnose disease. Fifty-percent concentrations of botanical were extracted from dried leaves using a methanol-based solvent extraction method. Two sets of partially ripened non-infected marketable papaya fruits were collected and treated with 50% concentration of botanical extracts and allowed to dry. One set was coated with melted wax by spraying under cool conditions using a power sprayer, along with a non-treated control. These experimental setups were arranged in a complete randomized design with five replicates. Four hours after wax coating, both sets were inoculated with spores of C. gloeosporioides. Data on disease incidence, disease severity (0–5 scale), number of days for disease-free period, pH, and TSS were measured in both sets and ANOVA was performed using SAS software. Duncan’s Multiple Ranges Test (DMRT) was used to determine the least significant differences among the treatments at p < 0.05. The results show that disease incidence and severity in O. basilicum + bee wax treated fruits was 0% and 5%, respectively, and significant at p < 0.05 until the 10th day post-inoculation; thereafter, disease incidence and severity were slowly increased to 15% on the 14th day post-inoculation, but in other treatments and the control, disease incidence and severity varied from 60–80% and 100%, respectively, from the fifth day post-inoculation. Moreover, bee wax-coated papaya fruits showed significantly higher preserved days, to a maximum of 17.047 ± 3.86. Weight loss percentage, pH and TSS were not significantly on par among wax-coated treatments but were significant when compared with wax-free treatments. This study concludes that the combined application O. basilicum + bee wax is a promising alternative to nasty fungicides.

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The important cash crop of Chilli's (Capsicum annum L) production and yield is hampered by Chilli Leaf Curl Virus Disease (CLCVD) in Sri Lanka. To manage CLCVD several insecticides were promised against the vectors of CLCV. Indiscriminate use of insecticides created unwanted human health hazards. The current trends in plant pathology intend to boost the immunity of the host to increase the resistance against pathogens. Therefore, this study was conducted to investigate the efficacy of Sea-Weed Extract (SWE) to manage CLCVD. The chilli variety Vijaya was selected for this experiment with five treatments and a non-treated control, which were arranged in RBCD. Data on growth parameters, yield, aphid severity, and CLCV disease severity Index (DSI) were measured and subjected to ANOVA in SAS and Tukey's HSD multiple comparison test was used to identify the best treatment combination at P <0.05. The results showed that first application of Sea-Weed Extract (SEW) at 15 days after planting with subsequent application of SWE at 15 days interval + application of insecticides at 10-15 days interval (T4) significantly lowered the CLCV DSI of 40.24%, less aphid severity index of 5.16% with the highest chilli yield of 436.8 kg/ha. The investigation concluded that SWE induces plant immunity but no effect on vector control. Therefore, SWE with recommended insecticides is better to increase the immunity of plants for the effective management of CLCVD.

Green gram (Vigna radiata (L.) R. Wilczek) is one of the most economically important grain legumes of the traditional farming systems of Sri Lanka because it is a cheap source of protein and animal feed, and sustains soil fertility by fixing atmospheric nitrogen. Weeds are one of the major problems in green gram cultivation, reducing the yield through competition, interference with harvest and harboring pests and diseases. Controlling of weeds by applying herbicides would definitely cause unexpected damage to human health and the abundant biodiversity of Sri Lanka. Therefore, an investigation was planned to evaluate the yield loss due to weeds and to determine the optimum weed free period to minimize the yield losses. Two experiments were performed. The first experiment was conducted to determine the effects of different weed functional groups on the yield of green gram. In the second experiment, weeds were continuously hand weeded and areas kept weed free. In the third, weeds were allowed to compete with green gram until 2, 3, 4, 5 or 6 weeks after cultivation. All the treatments were conducted in randomized complete block design with three replicates. The data collected on types of weed, number of pods and pod weight at 3–6 weeks after planting (WAP) were analyzed using the SAS 9.4 statistical package, and DMRT was performed to determine the best treatment combination. The results from the first experiment showed that average yield loss due to total weed populations was 54.77%. Yield loss due to grasses alone was 46.56%, far worse than broad leaves (16.49%) and sedges (18.01%) at p < 0.05. Crop stand count at 3–4 WAP was not significantly different among treatments. However, biomass weight of 50 plants, number of pods in 50 plants and grain weight of 10 plants were found to be significantly different after 3–4 WAP in weed free conditions at p < 0.05%. When the weed free period increased, the yield was increased until 3 WAP; thereafter, not significant yield increment was observed. In contrast, yield steeply declined in plots that had weeds until 3 WAP. According to the results of the present study, it can be concluded that the critical weed free period from the planting of green gram is 3 WAP. Maintaining a weed free period for 3–4 weeks is recommended to minimize the yield loss of green gram at minimal weed management cost.