Banana cultivation issues in Pakistan - Dissertation Sur Agriculture

Global production of sweet banana is facing serious threat from Fusarium oxysporum f. sp. cubense (Foc), pathogen of Panama disease. Current banana cultivar, the Cavendish, replaced Gros Michael during the mid-twentieth century after devastation caused by Foc race1 and now it covers 99% of global banana trade. Race4, the new Foc strain, is virulent not only to Cavendish but other banana cultivars as well. For more than a decade this strain remained restricted in banana fields of South-East Asia but since 2010 it has spread to Africa, the Middle East and Latin American regions. Overall the global banana industry, according to the export figures of 2016, generates approximately USD 8 million per annum (FAOSTAT). Today commercialized Cavendish cultivar accounts for 47% of global banana with 50 billion tonnes per anum production (FAOSTAT, 2018).

In Pakistan the dwarf Cavendish banana (Hari chhal), locally known as Basrai, was brought in Sindh from Bombay in 1913 and its cultivation became commercialized in 1950s. Since then it has grown on 34 hectares and now covers approximately 90% of area under cultivation in Sindh (Bhatti, 1991; Khalid and Soomro, 1993; Junejo, 2014) while varieties like William Hybrid and recently introduced variety Grand Naine (G-9) accounts for 10% of area under cultivation. Ninety percent of banana production in the country is received from Sindh and 10 % from Baluchistan Province (Junejo, 2014). Banana has become an important export commodity for the country and has earned 2.5392 million US dollars in 2011. Since the TR4 susceptible dwarf Cavendish cultivar is the predominant variety in the region, it puts the entire banana production line of Pakistan under serious threat.

Fusarium wilt of banana is a polycyclic disease (Ploetz, 2015b) implying that even small amounts of pathogen infested fields can cause devastating losses, even though initially it may raise little concern. Although only a few banana fields in Thatta district, Sindh province, Pakistan have been detected with Fusarium wilt infestation yet if taken lightly it could eventually develop into an uncontrollable problem like in the Philippines and China (Buddenhagen, 2009). Foc can persist in the soil as chlamydospores and prevents the replantation of susceptible varieties for up to 30-40 years (Stover, 1962, 1990; Simmonds, 1966; Buddenhagen, 2009), therefore crop-rotation is considered to be ineffective for the management of the Fusarial wilt disease (Stover, 1962).

Presently there exist no effective integrated models of disease management for banana Fusarium wilt because unlike other nefarious

pathogens of banana, like Black Sigatoka, burrowing nematodes, and banana bunchy top, that can be managed via pesticide use, the same strategy has been proven to be ineffective when it comes to Fusarium wilt disease management (Burgess et al., 2008; Guilford, 2014; Ploetz 2015b; Nel et al., 2007). Likewise, cultural and physical methods have also shown little efficacy in this domain (Guilford, 2014; Ploetz 2015b).

An alternative biological method, as antagonistic microorganism, could prove optimistic against Foc, as the studies in the recent era have found that the microbial approaches hold key potential in effective management of plant diseases especially the soil-borne pathogens (Weller et al., 2002 ; Belgrove et al., 2011; Mendes et al., 2015; Shen et al., 2015; Cha et al., 2016). Developing suppressive soils for efficient plant disease management requires exploration of indigenous microbiota having potential for antagonism against the soil-borne pthogens. Therefore the current investigation was aimed to evaluate bio-control efficacy of Trichoderma spp. native, isolated from banana fields of Sindh province, on Fusarium oxysprum f. sp. cubense (Foc) under in-vitro and greenhouse conditions.

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