**7. Conclusions**

was initially developed in 1974, which demonstrates the considerable lag from introduction

Verticillium wilt continues to be an import disease for the Australian industry. However, there have been major successes in developing cultivars with good resistance to this disease. A major breakthrough was the release of Sicala V-1 in 1991, the first CSIRO cultivar with significant resistance, and its higher yielding replacement, Sicala V-2 in 1994. These cultivars show greatly reduced levels of infection, less severe symptoms and higher yields compared to their predecessors and have transformed those regions where Verticillium wilt severely limited yields. None of the parents of the population these cultivars were developed from had significant resistance to Verticillium wilt and would generally have been considered suscep‐ tible. The source of resistance has therefore been considered to be the result of additive effect of alleles at multiple loci. Molecular techniques may one day be able to determine the source

After Fusarium wilt was first identified in Australian cotton in the early 1990s, new cultivars were required to allow viable production in the regions where the disease was present. It was quickly established that there was cultivar variability for resistance and a few cultivars did show some degree of resistance (Sicot 189, Delta Emerald). Most other commercial cultivars were very susceptible to the disease and had survival rate of close to zero in some situations. An initial screen from the CSIRO germplasm collection in 1994 tested 36 *G. hirsutum* genotypes from the USA, South America, Africa, Asia and Europe. As with the local cultivars, most were susceptible, but a few genotypes showed field survival up to 50% higher than the best Australian cultivars. Over the next few years over 200 genotypes from the collection were evaluated, with material from countries/regions/programs that showed promise in the early evaluations targeted. In 2004 a new cultivar, Sicot F-1, was released from the CSIRO breeding program which had at least twice the resistance of the best cultivar in 1994. Progress in breeding for improved Fusarium resistance continues, with the initial sources of resistance being derived from Indian and Chinese *G. hirsutum* parents and more recently, improved resistance

The key to the breeding success of soil borne fungal diseases has been the availability of screening sites with high levels of inoculum and therefore the opportunity for selection of reduced disease incidence and symptoms, together with high yield. The germplasm collections

The okra leaf (OL) mutant of upland cotton is characterised by deep lobing and some reduction

considerable research has been done on the effects of this leaf shape, only in Australia have OL cottons been grown on a major scale, accounting for between 40-60% of Australian seed sales between 1987 and 1993. As reviewed by Thomson [6] the published benefits of OL include host plant resistance to a range of insect and mite pests (boll weevil *Anthonomus grandis*, whitefly *Bemisia tabaci*, spider mites *Tetranychus spp.* and bollworms *Heliothis* and *Helicoverpa spp.*), earlier maturity, increased water-use efficiency and reduced boll rot. However, the OL

allele is partially dominant over the normal leaf (l2) shape. Although

of a trait to commercial release.

24 World Cotton Germplasm Resources

and composition of this resistance.

from *G. hirsutum* and *G. barbadense* landrace cottons.

**6.2. Commercial utilisation of the okra leaf mutant**

o

in leaf area. This L2

have been invaluable in accessing material for evaluation of resistance.

The challenge of maintaining genetic diversity in this era of fierce intellectual property protection and commercial reality is significant. One of the ways this is being addressed in the CSIRO breeding program is by developing diversity through utilisation of the genetic resources outside the cultivated tetraploids. This can mean using landrace cottons, but more importantly evaluating traits in the secondary germplasm pool (A and D genomes) and accessing those traits by developing synthetic tetraploids. This approach to diversity requires considerable effort and a long-term vision; however, it does have the potential to pay sub‐ stantial dividends in unlocking traits previously unavailable from within elite cultivars. To justify this approach, there generally must be present a crucial trait of commercial importance not available in existing germplasm and/or forward-looking funding.

Access to a broad germplasm pool and the ability to import material from other breeding programs combined with rigorous selection regimes for yield and quality under the unique Australian climate has meant that the CSIRO cotton breeding program has maintained yield progress while many other programs are plateauing in yield. Australian cultivars have had considerable success in the US, particularly Texas where there are some similarities in climatic challenges and are now being marketed worldwide under the FiberMaxTM brand.

ment of Cotton: emerging technologies. Enfield, New Hampshire: Science Publishers,

Australian Cotton Germplasm Resources http://dx.doi.org/10.5772/58414 27

[8] Fitt GP, Wilson LJ, Kelly D, Mensah R. Advances in integrated pest management as a component of sustainable agriculture: The case study of the Australian Cotton Indus‐ try. In: Peshin R, Dhawan AK, editors. Integrated Pest Management: Innovation-De‐

[9] Wilson LJ, Mensah RK, Fitt GP. Implementing IPM in Australian cotton. In: Horo‐ witz AR, Ishaaya I, editors. Novel approaches to insect pest management in field and

[10] Wilson LJ, Bauer LR, Lally DA. Insecticide-induced increases in aphid abundance in

[11] Wilson LJ, Bauer LR, Lally DA. Effect of early season insecticide use on predators and outbreaks of spider mites (Acari : Tetranychidae) in cotton. Bulletin of Entomolo‐

[12] Wilson L, Downes S, Khan M, Whitehouse M, Baker G, GRundy P, et al. IPM in the transgenic era: A review of the challenges from emerging pests in Australian cotton

[13] Constable G, Llewellyn D, Wilson L, Stiller W. An industry transformed" The impact of GM technology on Australian cotton production. Farm Policy Journal 2011;8(1):

[14] Gunning RV, Byrne FJ, Conde BD, Connelly MI, Hergstrom K, Devonshire AL. First Report of B-Biotype *Bemisia-Tabaci* (Gennadius) (Hemiptera, Aleyrodidae) in Austral‐

[15] Sequeira RV, Naranjo SE. Sampling and management of *Bemisia tabaci* (Genn.) bio‐

[16] Werth JA, Preston C, Roberts GN, Taylor IN. Weed management practices in glypho‐ sate-tolerant and conventional cotton fields in Australia. Aust Journal of Experimen‐

[17] Charles GW, Taylor IN. Herbicide resistance and species shift in cotton: the need for an integrated weed management (IWM) approach. In: Swanepoel A, editor. World Cotton Research Conference-3; Cape Town, South Africa: Agricultural Research

[18] Allen SJ. Predominance of race 18 of *Xanthomonas campestris* pv. *malvacearum* on cot‐

[19] Schnathorst W, Evans G. Comparative Virulence of American and Australian Isolates of *Verticillium-albo-atrum* in *Gossypium hirsutum*. Plant Disease Reporter 1971;55(11):

ia. Journal of the Australian Entomological Society 1995;34:116-20.

type B in Australian cotton. Crop Protection 2008;27(9):1262-8.

Council-Institute for Industrial Crops; 2003. p818-28.

ton in Australia. Plant Disease 1991;75:43-4.

velopment Process: Springer Science and Bussiness Media BV; 2009. p507-24.

protected crops. Netherlands: Springer Press; 2004. p97-118.

cotton. Australian Journal of Entomology 1999;30;38:242-3.

systems. Crop and Pasture Science 2013;64:737-49.

Inc.; 2001. p1-15.

gy Research 1998;88(4):477-88.

tal Agriculture 2006;46(9):1177-83.

23-41.

977-80.

New DNA sequencing technologies will accelerate the identification of genes involved in important agronomic traits, and via marker assisted seed selection, new and novel traits will be introgressed into elite cultivars that should further improve Australian cotton yield and quality.
