Introduction

In Sinaloa, a wide range of vegetables are grown, of which Solanaceous and Cucurbitaceous crops stand out. The first group includes the potato (Solanum tuberosum), tomato (Solanum lycopersicum), pepper (Capsicum annum) and husk tomatoes (Physalis philadelphica), which, in the fall-winter season of 2022, covered a surface of 11,975.1; 11,541.2; 15,172.4 and 7,317.9 ha, respectively. Meanwhile, cucurbitaceous crops are represented by different types of pumpkin and cucumber that cover a surface of de 2,686.2 and 3,874.9 ha in the same growing season. The annual value of the production of solanaceous crops reached 13,618,770,410 pesos, while cucurbitaceous crops reached 2,511,114,370 pesos (SIAP, 2022).

From an agronomic point of view, weeds are considered a significant threat to agricultural production, since they compete for nutrients, space, water and light with cultivated plants (^{Zimdahl, 1980}; ^{Dille et al., 2016}). On the other hand, although ruderal plants do not compete with the growth of crops, they become undesirable, since they grow along roadsides and in vacant lots in towns and cities, as well alongside railways and in the embankments of drains and channels, limiting the flow of water during heavy rainfalls, causing the accumulation of sediments, which leads to floodings. In addition, both plant types can be sources of inoculum for the development of diseases in economically important crops. These types of plants can act as hosts for plant pathogens and vector insects that spread diseases from these to economically important crops. The symptoms caused by diverse diseases are more evident in cultivated plants than in wild ones, due to several factors: a) The greater genetic diversity in wild plants than in cultivated plants, b) heterogeneity of the wild populations and the limited contact between plants of the same species, c) natural selection in time, which leads to a species becoming resistant or tolerant to a certain pathogen, and d) the natural elimination of wild plants susceptible to highly virulent pathogens (Wisler and Norris, 2000). There are many records of cases in which wild plants are involved as sources of inoculants of diseases caused by viruses (^{Duffus, 1971}; ^{Yazdkhastia et al., 2021}; ^{Korbecka-Glinka, 2021}) and fungi (SAGARPA-SENASICA, 2016; ^{Gerling et al., 2022}).

This study addresses of viral and fungal diseases that have been found in weeds and ruderal plants and which display a potential for spreading to horticultural crops in northern Sinaloa.

Viral diseases. In the complexity of the epidemiology of viral agents, wild and cultivated plants, as sources of inoculum for the development of diseases (Table 1), as well as the insect population and its motility, are important elements for the incidence of this type of diseases. Weeds and ruderals can be infected by viruses introduced to an area of cultivated plants, and then serve as a permanent source of

inoculum for other cultivated plants (^{Broadbent, 1964}). Although this aspect remains unexplored in Sinaloa, the possibility that many of the viruses that currently cause diseases in vegetable crops entered via seeds or other ways to spread diseases is not discarded, as well as the viruses being transmitted from cultivated plants to wild plants, where insect vectors play a crucial role in the development of epidemics.

Potential sources of viral diseases in tomatoes for processing. The viral diseases in processing tomatoes significantly limited the production in northern Sinaloa in the 1990s. Studies in which geostatistical tools were used indicated a high correlation between the presence of weeds and ruderals of the families Malvaceae, Sterculiaceae, Euophorbiaceae, Nyctaginaceae and Leguminaceae, with symptoms induced by geminivirus. Addditonally, species of the family Solanaceae displayed incidence of Tobacco etch virus (TEV), Pepper mottle virus (PepMoV), Cucumber mosaic virus (CMV) and Tomato spotted wilt virus (TSWV). The presence of symptomatic plants and populations of whiteflies, aphids and thrips was highly correlated with the incidence of these viruses in tomatoes for processing. Furthermore, Geographic Information Systems (GeoEAS; USEPA-LV.EAD, Las Vegas, NV), studies on the analysis of risk variables (^{Myers, 1991}), as well as the application of the 5x5 km grid using the Kriging system for risk estimation (^{Isaaks MJ. 1989}; Myers, 1991) helped on determining sectors of northern Sinaloa with incidences ranging between 0 and 2% and others with incidences between 25 and 100% of viral diseases in tomato. Based on this information, a management system was designed and validated for viral diseases in the crop, which consisted of the selection of the irrigation districts with the lower risk of incidence of this type of disease, and where the planting stage was considered, along with the elimination of weeds and ruderals in an area of 200 m adjacent to the vegetable plantations, in the districts that displayed a high risk of incidence of these diseases (^{Nelson et al., 1994}). During the time of the development of this study, 7,000 ha of sugarcane (Saccharum officinarum) were planted in northern Sinaloa, which displayed large weed populations infected with the Tobacco etch virus (TEV), the cucumber mosaic virus (CMV) transmitted by aphids, geminivirus complex transmitted by whiteflies, the Tomato spotted wilt virus (TSWV) transmitted by thrips, and the Tomato mosaic virus (TMV) with an unknown vector. Meanwhile, the weeds were colonized by the insect vectors mentioned above, which transmitted them to tomato plantations for processing. Nowadays, sugarcane is not being planted in the area, and undoubtedly, the level of risk of incidence of viral diseases has decreased. However, in recent years, the Tomato apex necrosis virus (ToANV) (^{Barajas-Ortiz, 2013}) and the Zucchini yellow mosaic virus (^{Félix-Gastelum et al., 2007}) have emerged, which justifies regional studies, such as the one carried out in the 1990s and the subsequent implantation of this system for the management of viral diseases in vegetable plantations.

The Tomato apex necrosis virus in tomato and tomatillo. In the past 10 years, studies have been carried out on the detection of the Tomato apex necrosis virus (ToANV). The disease caused losses in 100% of tomato and husk tomatoes transplants in the El Fuerte and del Carrizo Valleys on 400 and 300 ha surfaces with both crops in the 2011-2012 and 2012-2013 cycles. The damages were observed mainly in the transplanting of susceptible hybrids established in September. Despite the small whitefly (Bemisia tabaci) populations, the populations of wild plants with viral symptoms were large due to summer rains, indicating a high efficiency of the whitefly as a vector. Symptoms in tomato consist on necrosis of young plant and fruit buds (Figures 1 A and B). In husk tomatoes, symptoms initially appear as a mosaic in leaves and in advanced stages of the disease, they become entirely yellow (Figure 1C), followed by the plant in general (Figure 1), with effects on the vigor

Figure 1 Symptoms induced by Tomato apex necrosis virus (ToANV). A) Necrosis in young growth of tomato; B) Necrosis in tomato fruit; C) interveinal chlorosis in leaves of husk tomato; D) Yellowing in wild husk tomato (Physallis sp.); Slight yellowing and deformation of initial leaves in black nightshade (Solanum nigrum); F) Initial symptoms of interveinal chlorosis; G) Intense chlorosis and vein greening of wild tobacco (Nicotiana glauca) leaves; H) General yellowing in black nightshade (Solanum asureum). 

and limiting the production and quality of this vegetable, to the extent in which farmers destroy the crop in order to plant maize (Zea mays) or sorghum (Sorghum bicolor) (^{Espinoza-Castillo, 2013}).

The ToANV has been detected in weeds and ruderals of the family Solanaceae using serological and RT-PCR tests, such as wild tomatillo (Physalis sp.) (Figure 1D), black nightshade (Solanum nigrum) (Figure 1E), jimsonweed (Datura sp.), wild tobacco (Nicotiana glauca) (Figures 1F and G) and nightshade (Solanum asureum) (Figure 1H). Additional tests indicated that whiteflies transmit the virus to tomatillo and tomato from wild plants (mentioned earlier) (^{Espinoza-Castillo, 2013}). These findings coincide with previous results that indicate that the virus is transmitted by whiteflies (^{Barajas-Ortiz, 2013}). These potential sources of inoculum are widely distributed in northern Sinaloa and frequently display viral symptoms, which coincides with large vector populations and husk tomatoes and tomato crops. The management of this disease has focused on the use of virus-tolerant tomato varieties and the management of whitefly using systemic insecticides in applied through pressurized irrigation systems and the elimination of plants as potential sources of inoculum, which is precisely followed up by the la Local Plant Health Board of the Valley del Fuerte.

Wild Cucurbitaceae as sources of inoculum for viral diseases in zucchini squash. Preliminary studies in the El Valle del Fuerte indicate that in zucchini, the infections that take place are caused by the Zucchini yellow mosaic virus (ZYMV) (Figure 2A and B), the Watermelon mosaic virus (WMV), the Papaya ring spot virus (PRSV-W) and the Cucumber mosaic virus (CMV), both individually and as coinfections in commercial plots with this crop. Meanwhile, wild tobacco (Nicotiana glauca), wild cantaloupe (Cucumis melo var. Dudaim), bitter melon (Momordica charantia) and prickly cucumber (Cucumis dipsaceus) plants displayed the same viruses (^{Félix-Gastelum et al., 2007}). Finding these viruses in weeds and ruderals indicates that these can act as sources of inoculum for the development of viral diseases in other cucurbitaceous crops planted in the region, which must be proven through inoculation tests under greenhouse conditions with insect species previously reported as vectors for this type of virus. Studies in Mexico indicate that N. glauca is a CMV reservoir, which coincides with studies in Greece, where the same ruderal is a source of inoculum for the same virus (^{Volvas and Di Franco, 2004}).

Diseases caused by fungi. Fungal diseases in weeds and ruderals have received less attention than cultivated plants, since they cause economic losses in the latter, whereas wild plants frequently remain unnoticed in natural environments. Some plants act as alternate hosts, which is essential in the life cycles of diseases. In this regard, wheat rust stands out, caused by Puccinia graminis f. sp. tritici, which infects the alternate host (Berberis vulgaris) with basidiospores and genetic exchange takes place, to form aecia and aeciospores that infect the wheat plant once again. This allows the biological cycle to repeat itself (^{Leonard and Szabo, 2005}). It is also known that in Germany, on the edges of “kettle holes,” different species

Figure 2 Symptoms induced by the virus Zucchini yellows mosaic virus (ZYMV). A) Yellowing in Zucchini squash var. Grey leaf; B) Symptoms of deformation of the fruit of the same host caused by the same virus. 

of Poaceae and herbaceous plants grow, which are infected by up to 12 species of Fusarium in the autumn-winter, and which have the potential to cause diseases in agricultural crops (^{Gerling et al., 2022}). Similarly, Phomopsis sp., Phomopsis longicolla and Diaporthe phaseolorum, isolated from the weeds Eclipta postrata, Ipomea lacunosa and Desmenthus illinoensis caused diseases in hypocotyls, pods and seeds in soybean plants (Glycine max) (^{Mengistu et al., 2007}). The following describes weeds and ruderals as potential sources of inoculum for the development of fungal leaf diseases in Sinaloa.

Powdery mildew (Golovinomyces spadiceus) on wild sunflower (Helianthus annus). Studies on the powdery mildew on wild sunflower (Figure 3D) indicated that G. spadiceus is the causal agent of the disease in Sinaloa and it caused the disease in commercial sunflower in artificial inoculations (^{Félix-Gastélum et al., 2019}). This study is important, since wild sunflower can serve as a source of inoculum for the development of the disease in cultivated sunflower. It is important

Figure 3 Symptoms induced by fungus in weeds. A) Light to dark brown lesions and browning of the leaf sheath in Johnsongrass (Sorghum halepense) plants, caused by Curvularia muehlenbeckiae; B) Symptoms of powdery mildew caused by Golovinomyces spadiceos in a wild sunflower leaf (Helianthus annus); Irregular to circular brown spots, on a leaf of castor bean plant (Ricinus comunis) caused by Alternaria sp. Irregular to circular brown spots, on a leaf of castor bean plant (Ricinus comunis) caused by Alternaria sp.; F) Symptoms of downy mildew caused by Pseudoperonospora cubensis in wild melon (Cucumis melo var. Dudaim). 

to emphasize that wild sunflower grows as a weed, competing with maize (Zea mays), bean (Phaseolus vulgaris) and other crops, as well as growing as a ruderal plant on the edges of roads, embankments and slopes of drains and canals in the winter and early spring, coinciding with the commercial sunflower cultivations in the region.

Foliar blight (Alternaria spp.) in wild tobacco (Nicotiana glauca). Wild tobacco is a perennial solanaceous plant that grows alongside of, embankments and slopes of irrigation channels and drains, as well as in vacant agricultural fields. This ruderal appears as light to dark brown lesions in irregular shapes on leaves (Figure 3B) during the autumn-winter cycle. The severity of the disease increases when the daily periods of wet foliage range from 15 to 18 h and temperatures fluctuate between 14 and 28 °C; under these conditions, defoliation of the basal third of plants occurs. Preliminary studies showed that an unidentified species of Alternaria (^{Simmons, 2007}) is the causal agent of the disease (^{Apodaca-Orduño, 2016}). In artificial inoculations, the fungus proved to be pathogenic in tomatoes, causing light to dark brown lesions with concentric rings (Figure 3C), similar to those of early blight caused by A. solani (^{Sánchez-Castro, 1998}) y A. tomatophila (^{Jones et al., 2017}). These results show that wild tobacco is a potential source of inoculum for the development of early blight in tomato, caused by a new species of Alternaria in Mexico and other parts of the world.

Leaf blight in coyote tobacco (Nicotiana trigonophylla) and black nightshade (Solanum nigrum). Coyote tobacco and black nightshade are annual plants that grow during the autumn and winter, mainly appear as weeds and rarely, as ruderals. In recent years, these plants displayed irregular, light to dark brown lesions measuring 3.0 to 5.0 mm. With the progress of the disease, the lesions acquire an irregular shape and can cover up to 50% of the infected leaf. When the lesions coalesce and cover up to a third of the leaf, defoliation begins, mainly on the basal leaves of the plants. Two species of Alternaria belonging to the section Alternata and Curvularia muehlenbeckiae (^{Guerra-Meza, 2021}) were consistently isolated, yet their pathogenicity has been proven in them or in cultivated Solanaceae.

Leaf blight (Alternaria sp.) of Johnson grass (Sorghum halepense). Johnson grass is an annual Poaceae that is found as a weed and ruderal all year round in Sinaloa. In the autumn, winter and spring, the plants display light to dark brown interveinal lesions measuring 1.0 a 2.0 cm (Figure 3). The lesions increase their size until they cover 50% of the area of the leaf. Studies carried out in Sinaloa indicate that the disease is caused by Curvularia muehlenbeckiae (^{Olivas-Peraza et al., 2021}). The fungus has also been reported to cause leaf spots on guar (Cyamopsis tetragonoloba) in Sinaloa (Tovar et al., 2022). Soybean is the only economically important host in which the fungus C. muehlenbeckiae causes leaf spots in Sinaloa; it has also been recorded that it causes leaf lesions in pecan trees (Carya illinoinensis) in China (^{Lv et al., 2023}) and firs (Cunninghamia lanceolata) (^{Cui, 2020}), also in Chin. In Sinaloa, the fungus has been found to be associated to leaf spot on coyote tobacco (Nicotiana trigonophylla) (^{Guerra-Meza, 2021}). Although soybean leaf blight is caused by C. muehlenbeckiae in Sinaloa, whether Johnson grass, guar and coyote tobacco can act as potential sources of inoculum for the development of the disease is unknown. Hence the importance of cross-inoculating with isolates of the fungus from different plant species, which will contribute to the understanding of the ecology, epidemiology and management of the disease in economically important crops.

Leaf blight (Alternaria sp.) in castor bean (Ricinus comunis). The wild castor bean is considered an exotic invasive species that behaves as perennial when growing as ruderal in Sinaloa. Its leaves display irregular, light to dark brown spots measuring between 0.5 and 1.0 cm (Figure 3E); when the spots coalesce, they can cover up to 25% of the surface of the leaf, leading to defoliation, mainly in the leaves of the bottom third of the plants. Preliminary studies have proven that the leaf spot in the wild castor bean is caused by Alternaria ricini, and in artificial inoculations, also caused the disease in the commercial castor bean (^{Olivas-Peraza, 2018}), which coincides with earlier reports of the disease implicating A. ricini as the causal agent of the disease in commercial castor bean in Mexico (^{López-Guillén et al., 2015}) and in other parts of the world (^{Masirevic et al., 1993}; ^{Nagaraja and Krishnappa, 2016}a; 2016b). In Sinaloa, symptoms of leaf blight in wild castor bean are found during the autumn-winter, when the periods of relative humidity ≥ 90% from 12 to 16 h a day and temperatures fluctuate between 8 and 28 °C, which coincides with the cycle of the castor bean. Pathogenicity tests indicate that the wild castor bean plant is a potential source of inoculum for the development of leaf blight caused by A. riccini in cultivated castor bean.

Mildew (Pseudoperonospora cubensis) in wild melon (Cucumis melo var. Dudaim). Cantaloupe grows as a weed, but also as a ruderal in northern Sinaloa. It occurs in high populations in vacant agricultural fields during the summer and the early autumn in Sinaloa. In the past six years, this plant has displayed symptoms and signs of mildew. The disease is polycyclic and the plants display pale green to yellow, non-delimited spots on the upper side (Figure 3F), and on the lower side, the signs consist of sporangiophores and sporangia with a hairy, brown or purple growth. The incidence of mildew in cantaloupe is 100% and it destroys up to 50% of the plant foliage. The first symptoms of the disease in wild cantaloupe appear in the

last week in September and the first one in October, when the commercial cucurbits are still not transplanted in the region. The pathogenicity of P. cubensis from wild melon in cucurbits planted in Sinaloa has yet to be proven. However, studies in the United States indicate that P. cubensis survives the winter as an obligate biotroph in wild or cultivated cucurbits in Florida, whereas he pathogen does not survive the winter in the northeastern states of that country due to low temperatures in the winter. Thus, through wind dispersal and the presence of susceptible hosts in the dissemination path, the oomycete is spread from Florida to the northeastern states of the United States when the disease occurs during the spring and summer (^{Ojiambo and Holmes, 2011}). In Sinaloa, greenhouse plantations for the production of cucurbit seedlings begin on the first week in October. The sporulation of P. cubensis in wild cantaloupe is abundant and the levels of humidity and the temperatures favor the development of the disease, both in wild cantaloupe and cultivated cucurbits. However, the survival mechanism of the pathogen during the summer, when temperatures reach up to 40 °C, is unknown.

Weeds and ruderals as potential sources of inoculum in vegetable diseases in vegetable gardens in Sinaloa. This study addresses viral and fungal diseases that have been found in weeds and ruderals, and which have the potential to appear on vegetable crops. The importance of weeds and ruderals, as well as the abundance and motility of insect vectors of viral diseases in tomatoes for processing was proven in Sinaloa. Through studies on the presence of potential sources of inoculum and populations of potential insect vector species, a viral disease management species a viral disease management system was designed for tomatoes for processing (^{Nelson et al., 1994}).

Conclusions

In Sinaloa, a wide range of vegetables is planted. The incidence of viral and fungal diseases is frequent in solanaceae and cucurbitceae planted during the autumn-winter season in the area. At the same time, several species of ruderal weeds belonging to these and other botanical families display symptoms of viral and fungal diseases in the environment in which the produce is grown. The relationship between these pathogens with wild plants implies a risk of transmission towards the cultivated plants. To date there are no studies on the spatial and temporary distribution of weeds and ruderals in the valleys of Sinaloa, as well as the populational fluctuations of the vector insects of the viral diseases of this type of plants to cultivated plants and vice versa. There are also no modern systems to detect phytopathogens in plants or in potential vectors. Future research lines should address these topics, with the collaboration of botanists, entomologists, plant pathologists, and bioinformaticians; this will allow a sustainable management of diseases in vegetable gardens and other important crops in Sinaloa.