Prevalence of Fusarium Wilt of Tomato in Major Tomato Growing Areas of Punjab, Pakistan

Article History Received: October 02, 2021 Revised: November 24, 2021 Accepted: December 10, 2021 Tomato is an essential vegetable in the world due to its nutritional importance. It has vitamin A & C and lycopene, which reduce the prostate cancer, and heart and agerelated diseases. Tomato wilt disease (TWD) is a potential threat and spreading rapidly in tomato fields in Pakistan. The survey on the disease prevalence of Fusarium wilt (Fusarium oxysporum f.sp. lycopersici (Fol)) of tomato was conducted in the major tomato growing areas of Punjab, viz., Hafizabad, Pakpattan, Khushab, Sargodha and Faisalabad districts during the cropping season 2018. Tomato wilt disease incidence was higher in district Sargodha (94%) followed by Faisalabad (92%) and Khushab (65%). Two districts, Pakpattan and Hafizabad showed 86% and 73% incidence, respectively. The survey revealed that tomato disease incidence was prevalent with varying intensities in all surveyed districts of Punjab. Moreover, the variation in disease prevalence of tomato wilt disease in different locations was due to the environmental conditions of that area and the varieties being cultivated.


INTRODUCTION
Tomato (Lycopersicum esculentum Mill.) is a member of the family Solanaceae. It is originated from Peru, situated in South America. It is a precious horticultural crop for the market (Pritesh and Subramanian, 2011) and important due to its dietary components, which are contributing significantly to improve nutrition and health of both rural and urban populations (Waiganjo et al., 2006). Tomatoes are grown in all conditions, but give the best production in warm conditions where optimum temperatures are 15-30 °C (Hanaa et al., 2011). It is grown in both monsoon and winter Kharif and Rabi seasons (Nikhate, 2012). High humidity and temperatures reduce yields. While at the stage of ripening, temperature above 30 °C reduces the fruit yield.
Many factors can affect the yield and quality of tomato, among them; diseases play the most significant role (Pritesh and Subramanian, 2011). Commonly known diseases of tomato are early blight, anthracnose, bacterial wilt, bacterial canker, tomato spotted wilt, verticillium wilt and Fusarium wilt (Dodson et al., 2002). Tomato wilt disease (TWD) mainly caused tomato plant wilting, therefore referred as wilt disease. It is very important disease, either in field or greenhouse-grown tomatoes worldwide (Abdel-Fattah and Al-Amri, 2012; Amini and Sidovich, 2010;Sheu and Wang, 2006). The disease reaches at maximum level in tomato fields when wet conditions prevail on the fruit at maturity stage. Fusarium causes 20-80% losses per year worldwide (Nikhate, 2012). Characteristic symptoms of TWD are clearing of veins, leaves margins curling, leaves yellowing, stunting, development of adventitious roots, necrosis of blade of leaves, defoliation, and finally the whole plant died (Agrios, 1988;Srinivas et al., 2019). Disease assessment of plant diseases is not an easy method (Ajilogba and Babalola, 2013). Plant diseases are assessed on the basis of different symptoms produced by plants after infections and disease assessment is vital for estimating the yield losses caused by different plant diseases, development of disease simulating models and and organizing surveys are the best strategies for the estimation of yield losses caused by different fungal pathogens (Campbell and Neher, 1994;Ghuffar et al., 2018). As per our best information, for the first time, the present study plans to record the prevalence of TWD in multiple districts of Punjab. During this study, comprehensive surveys were planned to generate large data set of incidence of tomato wilt disease (TWD). The surveys were conducted in major tomato growing areas of Punjab, viz., Hafizabad, Pakpattan, Sargodha, Khushab and Faisalabad, Pakistan, during the tomato cropping seasons of 2019-20.

MATERIALS AND METHODS Surveys and collection of diseased samples
Surveys of most tomato wilt disease (TWD) affected districts of Province Punjab including Hafizabad, Pakpattan, Khushab, Sargodha and Faisalabad, Pakistan, was conducted in 2018 by using the GPS (GPS map76CSx, Garmin) tagging of these districts to determine the percent disease incidence (PDI) of TWD. The percent disease incidence of tomato wilt disease was determined by using following formula: Disease Incidence (%) = No. of tomato wilted plants Total number of tomato plants × 100 Data of percent disease incidence of TWD of each district was added in GPS and evaluated by ARCGIS and ARC View soft-wares to create the semi-variograms (Patel et al., 2016). Samples were collected from diseased tomato plants with typical symptoms and were placed in polythene zipper bags separately, labeled properly and stored in an ice box prior to isolations (Table 1). Tomato plants were grown in plastic pots having sterilized soil in greenhouse at 28 °C. Control of susceptible variety viz., Roma was also grown. Before inoculation, 2 to 3-week old plant roots were injured by repeatedly injecting a plastic peg into them. The inoculum, 110 9 spores/mL at 2-mL per pot, was drenched into the soil and allowed to penetrate into the rhizosphere. After fifteen days, symptoms were appeared (Fernández-García et al., 2012). Data was recorded every week according to the following disease assessment scale (Mir et al., 2011) (Table 2).

Statistical analysis
Disease incidence data was analyzed statistically using SAS (SAS Institute, NC, USA 1990). Analysis of variance (ANOVA) was used to test the main and interaction effects of the treatments. To check the effects of each treatment, means of each treatment were compared using LSD test at 5% level of significance (Steel et al., 1996).

RESULTS
For the spatio-variation, the selected five districts of Punjab such as Sargodha, Faisalabad, Pakpattan, Hafizabad, and Khushab were highly affected with TWD.

DISCUSSION
For the effective management of crop diseases, their assessment is vital (Campbell and Neher, 1994). Meteorological variables suitable for TWD development are relative humidity, temperature, intervals of leaf wetness and precipitation. Temperature 17 to 22 °C with 90% relative humidity is considered most suitable for TWD (Modesto et al., 2016). TWD caused by soil-borne fungus Fol is a major cause of yield losses in warm-temperate to tropical latitudes worldwide (Dodson et al., 2002). This disease causes wilting of the whole plant by entering from the roots and spreading via xylem fibers, blocking the movement of water (Cox et al., 2019). In this study, a survey of tomato wilt on farms was conducted in different areas of Punjab including Sargodha, Faisalabad, Pakpattan, Hafizabad, and Khushab. This survey revealed that fields in Sargodha had 94% incidence of tomato wilt, followed by Faisalabad (92%), Pakpattan (86%), Hafizabad (73%), and Khushab (65%). These results are in line with the findings of Heydari et al. (2007) and McGovern (2015). They reported 100% incidence of TWD in USA. Houterman et al. (2007) reported less prevalence of TWD on resistant cultivars, i.e., 0-29%, while 100% on susceptible cultivars in USA. Abdel-Fattah and Al-Amri (2012) reported 53-71% disease incidence while 47-78% disease severity of TWD in Egypt. Ishikawa et al. (2005) reported 50% disease severity in Japan, while Mandal et al. (2009) reported 40% TWD incidence in Japan in those fields where recommended foliar sprays of fungicides were applied. TWD is very notorious and has been reported in different countries even after the routine fungicidal applications, Iran 31-48%, Greece 45%, Thailand 80% and India 42% (Myresiotis et al., 2012). The survey noted tomato wilt symptoms including yellowing of leaves, disappearance of veins from the leaves, stunting, curling of leaves, emergence of new adventitious roots, defoliation of leaves, drying of stem and roots, and finally plant collapses and becomes dead (Agrios, 1988). These symptoms have also been reported in previous investigation (Fassihiani, 2000). Fol has the ability to produce the same symptoms in other Solanum spp. including S. pimpinellifolium and S. melogena (Fassihiani, 2000). There are hosts which carry Fol but do not produce symptoms; includes Chenopodium, Amaranthus, Malva, Digitaria and Oryzopsis spp. (Fassihiani, 2000). There are reports that legumes are very susceptible to Fol and show the same symptoms as observed on tomato (McGovern, 2015). Chlymadospores of Fol cause more severe symptoms in tomatoes than the macro-and micro conidia (McGovern, 2015). Fusarium spp. are versatile fungi that can survive on dead as well as living organic matter and persist in soil for years in the absence of host plants (Gordon, 2017). Fusarium spp. pervasive soil-borne pathogens that cause many diseases in horticulture and agronomic crops, including rots, vascular wilts, and damping-off (Bodah, 2017). Fol is a soil-inhabiting fungus having phylogenetic diversity (Xiong and Zhan, 2018). Warm weather, applications of ammonium containing fertilizers and low pH of soil exacerbate the symptoms of TWD (McGovern, 2015). Results from the current survey provided evidence of the prevalence and crop damage caused by tomato wilt in Punjab Province. This disease can undermine farm sustainability and rural livelihoods in Punjab, so it merits more intensive study in order to develop costeffective ways to reduce economic losses.