Management of seed / soil borne diseases of safflower by chemical and biocontrol agents

An experiment was carried out at the Oil seed Research Unit, Marathwada Krishi Vidyapeeth Parbhani, Maharashtra, India to evaluate the efficacy of different chemicals and bioagents against seed/soil borne diseases of safflower on disease incidence (PI or DI). Significantly low disease severity (DS) and low disease incidence (DI) were recorded in treatment withT7, that is, Trichoderma harzianum Th4d sc at 2 ml/kg to the tune of 41.66% in Fusarium sp, 08.33% in Rhizoctonia sp, 06.66% in Phytophthora sp, 04.33% in Alternaria leaf spot and 03.33% in Cercospora leaf spot , respectively, in comparison with the untreated control. The seed yield data indicated that T. harzianum produced highest seed yield (2778 kg/ha) followed by Captan at 0.2% (2115 kg/ha) and Carbendazim+Mancozeb (SAFF) at 0.2% (2114 kg/ha). High infestation of safflower seeds by causal agents of seed/soil borne foot and root rots, reduction of seed germination and considerable infection transmission from seed to seedling were determined. Fungicide seed treatments, T1 to T8, markedly decreased incidence of diseases. Though the treatment with T7, that is, T. harzianum recorded the disease incidence, it produced the highest yield.


INTRODUCTION
Safflower (Carthamus tinctorius L.) is one of the most important oilseed crops of the world valued for its highly nutritious edible oil.It is a multipurpose crop having various uses like source of edible oil, cattle feed, medicinal and industrial products.Safflower is known to suffer from many fungal (leaf spot/blight (Alternaria carthami), wilt (Fusarium oxysporum f.sp.carthami), root rot (Rhizoctonia bataticola), powdery mildew (Erysiphe cichoracearum DC), anthracnose (Colletotrichum capsici) and charcoal rot (Macrophomina phaseolina (Tassi) Goid)), bacterial (leaf blight/spot (Pseudomonas syringae van Hall)) and viral diseases (mosaic (cucumber mosaic virus), necrosis (tobacco streak virus)) at different stages of crop growth (Jawalgaonkar, 1991;Bhale et al., 1998).Seed/soil borne pathogen particularly fungal pathogens affects directly and indirectly the quality and quantity of the oilseed crops in terms of deterioration and reduction in oil content, reduction in germination, viability of seed and potential losses in yields.As primary importance, it is the fact that seed borne plant pathogens introduce diseases into new areas previously free from such pathogens.In safflower, Fusarium wilt, Macrophomina root rot, Alternaria blight are known and reported as externally or internally seed borne fungi which are causing heavy losses to this crop.Keeping in view the importance of seed/soil borne mycoflora in safflower, the present study was conducted to study the effects of chemical and biomicrobial agents in reducing the impact of seed/soil borne diseases in safflower.The experiment was conducted at All India Coordinated Research Project on Safflower Marathwada Krishi Vidyapeeth Parbhani, Maharashtra, India.

MATERIALS AND METHODS
The efficacy of different chemicals and bioagents against seed/soil borne diseases of safflower on disease incidence (PI or DI) was done.The field experiment was conducted at Oil seed Research Unit Marathwada Krishi Vidaypeeth, Parbhani, Maharashtra, India during the Rabi season (15 October 2012 to 15 March 2013).The field experiment was carried out with eight different chemical and bioagents treatments in Randomized Block Design (RBD).Sowing was done at spacing of 45 m x 20 cm with dibbling method and variety used was Niera.In nine treatments, one control (untreated seed) treatment was carried out.Observations on disease incidence and also seed yield were recorded.
The recommended fertilizer dose of 60.30.20 kg N: P2O5:K2O/ha was applied.Nitrogenous fertilizers was applied in two splits, 50% at basal and 50% nitrogen was top dressed six weeks after sowings.Two irrigations were applied at sowing and just before flowering.The observations of various disease incidence percentage and seed yield were taken.
For this purpose, healthy seeds of safflower were selected and divided into two lots.First lot was treated by dry seed treatment, by each fungicide and biocontrol agents and second lot was kept as untreated control.The observations were used for statistical analysis.To compare two treatment means, critical difference (C.D.) at 5% level of significance was worked out.

RESULTS AND DISCUSSION
Results (Table 1) reveal that all the treatments recorded low disease incidence over control.The treatment metalaxy + mancozeb (Ridomil MZ) 0.02%, Folicur (Bayer)-250ml as well metalaxy + mancozeb (Ridomil MZ) 0.02%, significantly reduce incidence in Fusarium Rhizoctonia and Phytophthora, respectively.The treatment with Folicur, carbendazim at the rate 0.2% as well as captan reduce the incidence of Alternaria leaf spot and Cercospora leaf spot, respectively.Though these fungicides reduce the disease incidence, they did not produce higher yield as compare to T. harzianum Th4d sc at the rate 2 ml/kg.As mean per cent disease incidence ranged from 20.00 to 54.33% in Fusarium sp, 1.66 to 29.21% in Rhizoctonia sp, 3.33 to 8.33% in Phytophthora sp, 3.33 to 6.66% in Alternaria leaf spot and 0.00 to 15.03% in Cercospora leaf spot.
Result of different chemical and biocontrol treatments on the seed yield was found significant over control and ranged from 1692.55 to 2577.77kg/ha in comparison 1740.77kg/ha seed yield in control plot.Mean per cent disease intensity was found significant over control (27.56%).The lowest mean per cent disease severity (11.83%) was observed in T 4 treatment i.e. copper oxychloride 0.25% + streptocycline 100 ppm followed by carbendazim 0.1% + strpetocycline 100 ppm (11.95%), carbendazim 0.1% (13.81%) and copper oxychloride 0.25% + agrimycin 100 ppm (14.77%).Results obtained in respect of efficacy of chemical and bioagent in effectively inhibiting these pathogens are in conformity with those reported earlier by Nzojiyobiri et al. (2003), Gaurilčikienė et al. (2008) and Gaurilčikienė et al. (2012).
Results revealed that all the treatments recorded various per cent of diseases and yield.In these nine treatments, the treatment T6, was found significantly superior in the management of Fusarium.The treatments T1, T2, T3, T4 T5 T7 and T8 were at par with T6.The treatment T9 was not significant and T6, T5 were at par with T9.The incidence percentage of Rhizoctonia was low in the treatment T5 which was a superior treatment.The treatments T3, T6, T7, T1 and T2 were at par with superior treatment T5.The treatment T9 was nonsignificant for Rhizoctonia.The treatments T4, T6 and T7 were at par with T9.For the management of soil borne Phytophthora, the treatment T5 and T6 were found significantly superior and the remaining treatments including check were found at par with superior T5 and T6.As there was no stagnant water in the field, the incidence of Phytophthora might be low.
Alternaria incidence was low in the treatment T5 and T6, which was significantly superior and all the remaining treatments excluding T9 were at par with superior treatment.This was recorded as the sowing was done at the recommended date and low humidity throughout the growing season.The treatments T2 and T3 were significantly superior for the management of Cercospora leaf spot.The remaining treatments were also at par with superior treatments.The result indicated that the biological agent seed treatment (T7) was significantly superior over rest of the treatments with respect to yield parameter.Though the diseases were recorded in the treatment T7, the yield was 2577.77kg/ha.It attributes that plant might tolerate the ill effects of diereses.The Trichoderma species might produces inhibitory substances or acetaldehyde compound against the test pathogens.
Biological control is an effective, ecofriendly and alternative approach for any disease management practice.The results on seed/soil borne diseases revealed that, all the chemicals and antagonists significantly reduced the incidence of diseases.Most of the antagonists inhibited the growth of pathogens, by their fast and over growing nature as observed in antagonists.Similarly, Deshmukh and Raut (1992) reported that Trichoderma harzianum Rifai and T. viride.Pers.overgrew colonies of Colletotrichum gloeosporioides and T. harzianum was more aggressive than T. viride . Santha Kumari (2002) observed that the isolates of T 1 and T 2 of T. harzianum and the isolates of A 1 and A 2 of Aspergillus niger were found effective in inhibiting the growth of C. gloeosporioides causing anthracnose of black pepper under in vitro condition.This can be attributed to higher competitive ability of these Trichoderma spp.The antagonism of Trichoderma spp.against many fungi is mainly due to production of acetaldehyde compound (Dennis and Webster, 1971).This may also be the reason for its antagonistic effect on seed/soil borne pathogens.Godtfredsen and Vagedal (1965) reported trichodermin, Pyke and Dictz (1960) found dermadin as major volatile antibiotic produced by Trichoderma spp., which suppress several plant pathogens.

Table 1 .
Management of seed/soil borne disease of safflower by chemical and biocontrol agents (seed treatment).
GMR, Gross monetary return; NMR, net monetary return, B:C ratio, benefit cost ratio.