WINETECH Technical Yearbook 2021

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7,47

FIGURE 3. Incidence of Trichoderma in the basal ends and roots of vines following different methods of application of Trichoderma post callusing. Data shown only for treatments that were repeated over two seasons. Pro uct 5 Basal end % Reduction

2016/17 2017/18

2 b

69,2307692

Product 1

3 BC

2016/17 2017/18

1,5 b

76,9230769

5,87 2,4

ots

120

4,5 BC

0 10 20 30 40 50 60 70 80 90

Product 6

19,33 15,67

100

ABSTRACT Black foot disease is one of the main fungal diseases associated with young grapevine decline. Trichoderma holds the potential to be used as a biocontrol agent against this disease. Therefore, two field experiments were established to evaluate different methods of application of Trichoderma atroviride , and to evaluate the effi cacy of different commercial Trichoderma products on black foot disease in nursery vines post callusing over two seasons. Only in one season of the trial evaluating different products did all of the Trichoderma treatments significantly lower the black foot infec tions in the rootstock bases of the vines. When comparing tissue parts, the base of the vine and root attachments had significantly higher Trichoderma colonisation than the central and root tip parts. Significantly less black foot pathogens were isolated from the base in comparison with the roots. The different application methods showed that dipping of moistened basal ends in the dry formulation followed by monthly soil drenches consistently gave higher colonisation, while the one hour soak of bases of vines was not effective and did not differ from the untreated control. Even though Trichoderma species were not sufficient to prevent all infections by black foot disease pathogens, a certain degree of protection was obtained in the basal ends, which may contribute to longevity of the vines once planted in the vineyard. b AB b C a ABC 2016/17 2017/18 2016/17 2017/18 2016/17

ends are often not completely healed or covered by callus tissue, and callus roots break off during the process, providing direct infection sites for BFD pathogens. The protection offered to the exposed basal ends by Trichoderma by means of competition for infection sites and antibiosis could aid in controlling the disease. The HWT of grafting material in combination with the dry product application was done in both seasons and showed that Trichoderma could successfully colonise the hot water treated material, and only resulted in significantly less colonisation in the first season from the dry product treatment. HWT (before plant ing) did not have an effect in the colonisation of BFD pathogens. However, BFD is often more severe when occurring together with other grapevine trunk diseases (GTDs) and infections often stem from infected propagation material. Therefore, minimising infec tions of other GTDs by means of HWT of dormant grafting ma terial is advantageous and will aid in cultivating healthier vines. Comparing the different Trichoderma-based products that were evaluated, in both seasons Product 5 resulted in higher Tricho- derma reisolation percentages from the basal ends, though not differing significantly from Product 3 (Figure 4). Interestingly, significant differences in the incidence of BFD infections were observed within the basal ends following treatments over both seasons, while no significant differences could be observed in the roots, again highlighting the protection offered by Trichoderma in the basal ends. The BFD infections in the basal ends were reduced by between 62% and 85% by the different product treatments in the first season. Although some of the products resulted in lower BFD incidences in the second season (reduction of 33% 67% in five treatments), it as not signi cantly different from the n treated control (Figure 5). From this study we concluded that the success of Trichoderma species as biocontrol agent und r nur ery field conditions dep nds not only on its antagonistic activity alone (as assessed by in vitro trials), but a combination of several other factors including the method of application, s w ll as ability of the is late to colonise the specific grapevine cultivar. Successful disease management requires an integrated disease management approach. Trichoder- ma may offe advantages as part of such a strategy where it can be used as a component with HWT and cultural measures. Other options need to be explored to lower BFD inoculum in the soil using, for example, biofumigation. b BC b BC b BC b b 0 2 4 6 8 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 BFD incidence (%)

2016/17 2017/18

2,5 b

61,5384615 -13,333333

Product 2

5,87 1,33

8,5 AB

2016/17 2017/18

1 b

84,6153846 46,6666667

4 BC

23,67 12

Product 7

2016/17 2017/18

2 b

69,2307692 66,6666667

Product 3

2,5 C

2016/17 2017/18

1,5 b

76,9230769 33,3333333

Trichoderma incidence (%)

5 BC

26,33 22

Untreated control

2016/17

2016/17 6,5 a

0 0

Product 4

2016/17 2017/18 Product 1 Product 2 Product 3 Product 4 Product 5 Product 6 Product 7 Untreated control 2017/18 7,5 ABC 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 Dry product + drenches 30min HWT + dry product Monthly drenches Soaking Untreated control 2016/17 1 b 84,6153846 2017/18 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 2017/18 2016/17

2016/17 Dry product

2017/18

2016/17 2017/18 Product 1 Product 2 Product 3 Product 4 Product 5 Product 6 Product 7 Untreated control 2017/18

2017/18

11 A

-46,666667

6 4,67

Basal end Roots

FIGURE 4. Incidence of Trichoderma in the basal ends and roots of vines following the application of different Trichoderma -based products. Data shown only for treatments that were repeated over two seasons. Basal end Roots URE 3. Incidence of Trichoderma in the basal ends and roots of vines following different methods of application of Trichoderma post callusing. a shown only for treatments that were repeated over two seasons. Pro uct 5 FIGURE 4. Incidenc of Trich derma in the basal ends and roots of vines following the application of different Trichoderma -based products. Data shown only for treatments that were repeated over two seasons. 2 b 69,2307692

Basal end FIGURE 5. Incidence of BFD pathogens in the basal ends following the application of different Trichoderma-based products. Data shown only for treatments that were repeated over two seasons. For the 2016/17 season all the treatments lowered the incidence of BFD significantly (P < 0.05) in comparison with the control. FIGURE 5. Incidence of BFD pathogens in the basal ends followi g the application of different Trichoderma -based products. Data sh wn only for treatments that were repeated over two seasons. F r the 2016/17 season all the treatments lowered the incidence of BFD significantly (P < 0.05) in comparison with the control.

2016/17 2017/18

37,67 20,33 120

3 BC

SUMMARY Black foot disease is one of the main fungal diseases associated with young grapevine decline. Trichoderma holds the potential to be used as a biocontrol agent against this disease. Therefore, two field experiments were established to evaluate different methods of application of Trichoderma atroviride , and to evaluate the efficacy of different commercial Trichoderma products on black foot disease in nursery vines post callusing over two seasons. Only in one season of the trial evaluating different products WINELAND JUNE 2021 incidences determined from 25 vines per replicate. Isolations were made from 1) the xylem and pith in the basal end, and 2) three sections of the roots, namely the rootstock attachment, central part and root tips. Fungal isolates representing any of the BFD pathogens or Trichoderma isolates were grouped and identified according to standard protocols. RESULTS AND DISCUSSION The two field trials showed that Trichoderma species, even after more effecti e colonisation, were not sufficient to prevent all infections by BFD pathogens. The efficacy of Trichoderma is in fluenced by the specific pathogen complex. In the current study the majori y of the BFD pathogens were found to be of the genus Campylocarpon , that are less sensitive to secondary metabolites produced by Trichoderma in vitro (data not shown). Analyses of the d erent tissue types revealed that in both tri als BFD infections of the roots were significantly higher than in 0 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 2016/17 2017/18 Basal end Roots Pr duct 6 2016/17 2017/18 Product 7 2016/17 2017/18 Untreated control 2016/17 2017/18 60 4 4

did all of the Trichoderma treatments significantly lower the black foot infections in the rootstock bases of the vines. When comparing tissue parts, the base of the vine and root attachments had significantly higher Trichoderma colonisation than the central and root tip parts. Significantly less black foot pathogens were isolated from the base in comparison with the roots. The different application methods showed that dipping of moistened basal ends in the dry formulation followed by monthly soil drenches consistently gave higher colonisation, while the one hour the basal ends of the rootstocks, while the opposite was true for Trichoderma as demonstrated with the different products trial in Figure 2. This effect was, however, variable over the two years. It appears as if Trichoderma were able to prevent pathogen infec tion of the basal ends where its colonisation was higher. When taking the results of the trial evaluating the methods of application of both seasons into account the highest reisolation perce tages of Trichoderma were obtained with the dry product application in combination with monthly soil drenches, or with 30 minutes HWT prior to grafting. In contrast, one hour soaking in a Trichoderma c nidial suspension prior to pla ting, d combinations thereof, were mostly ineffective and resulted in an outcome not different from the untreated control in either of the seasons (Figure 3). Different from the standard methods of application, the dry product application places high inoculum loads at the basal end of the graftlings before planting. At the time of planting the basal 2016/17 2017/18 2016/17 2017/18 2016/17 2,5 b 61,5384615 8,5 AB -13,333333 2 b 69,2307692 2,5 C 66,6666667 6,5 a 0 7,5 ABC 0

100

Foundation (NRF). The research was conducted at ARC Infruitec-Nietvoorbij and Stellenbosch University. The authors would like to express their gratitude towards the grapevine nursery involved, the ARC- Nietvoorbij technical team and Marieta van der Rijst (ARC Biometry Unit) for statistical analysis. Dr Ronel Hendriks is thanked for her contribution in the development of the new application method. ABSTRACT Black foot disease is one of the main fungal diseases associated with young grapevine decline. Trichoderma holds the potential to be used as a biocontrol agent against this disease. Therefore, two field experiments were established to evaluate different methods of application of Trichoderma atroviride , and to evaluate the effi cacy of different commercial Trichoderma products on black foot disease in nursery vines post callusing over two seasons. Only in one season of the trial evaluating different pro ucts did all of the Trichoderma treatments significantly lower the black foot infec tions in the rootstock bases of the vines. When comparing tissue parts, the base of the vine and root attachment had significantly higher Trichoderma colonisation than the central and root tip parts. Significantly less black foot pathogens were isolated from the base in comparison with the ro ts. The different application methods showed that dipping of moistened basal ends in the dry formulation followed by monthly soil drenches consistently gave higher colonisation, while the one hour soak of bases of vines was not effective and did not differ from the untreated control. Even th ugh Trichoderma species were not sufficient to prevent all infections by black foot disease pathogens, a certain degree of protection was obtained in the basal ends, which may contribute to longevity of the vines once planted in the vineyard. For more information, contact Lizél Mostert at lmost@sun.ac.za.

soak of bases of vines was not effective and did not differ from the untreated control. Even though Trichoderma species were not sufficient to prevent all infections by black foot disease pathogens, a certain degree of protection was obtained in the basal ends, which may contribute to longevity of the vines once planted in the vineyard. ACKNOWLEDGEMENTS The research was funded by Winetech and Department of Science and Technology (DST) . Wynand van Jaarsveld was supported by the National Research ends are often not completely healed or covered by callus tissue, and callus roots break off during the process, providing direct infectio si es for BFD pathogens. The protection offered to the exposed basal ends by Trichoderma by means of competition for infection sites and antibiosis could aid in controlling the disease. The HWT of grafting materi l in combination with the dry product application was done in both seasons and showed that Trichoderma could successfully colonise the hot water treated material, and only resulted in significantly less colonisation in the first season from the dry product treatment. HWT (before plant ing) did not have an effect in the colonisation of BFD pathogens. However, BFD is often more severe when occurring together with other grapevine trunk diseases (GTDs) and infections often stem from infected propagation material. Therefore, minimising infec tions of other GTDs by means of HW of dormant grafting ma terial is advantageous and will aid in cultivating healthier vines. Comparing the different Trichoderma- ased products that were evaluated, in both seasons Product 5 resulted in higher Tricho- derma reisolation percentages from the basal ends, though not differing significantly from Product 3 (Figure 4). Interestingly, significant differences in the incidence of BFD infections were observed within the basal ends following treatments over both seasons, while no significant differences could be observed in the roots, again highlighting the protection offered by Trichoderma in the basal ends. The BFD infections in the basal ends were reduced by between 62% and 85% by the different product treatments in the first season. Although some of the products resulted in lower BFD incidences in the second season (reduction of 33% 67% in five treatments), it was not significantly different from the un

7,67 5,67 60 80

12 12 20

Trichoderma incidence (%)

For more information, contact Lizél Mostert at lmost@sun.ac.za.

2016/17 2017/18 Product 1 Product 2 Product 3 Product 4 Product 5 Product 6 Product 7 Untreated control 2017/18

WINETECH TEGNIES JUL IE 2021

URE 4. Incidence of Trichoderma in the ba al ends and roots f vines following the application of different Trichoderma -based products. Data wn only for treatments that were repeated over two seasons.

dences determined from 25 vines per replicate. Isolations were de from 1) the xylem and pith in the basal end, and 2) three tions of the roots, namely the rootstock attachment, central t and root tips. Fungal isolates representing any of the BFD hogens or Trichoderma isolates were grouped and identified

the basal ends of the rootstocks, while the opposite was true for Trichoderma as demonstrated with the different products trial in Figure 2. This effect was, however, variable over the two years. It appears as if Trichoderma were able to prevent pathogen infec tion of the basal ends where its colonisation was higher.

WINETECH TECHNICAL YEARBOOK 2021 | 36

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