‘Marketmore 76’ has been widely planted since it was first introduced 30 years ago and represents one of the most successful cucumber cultivars ever released. Despite the subsequent development of numerous higher-yielding hybrids (Rowell et al., 2002), the elevated levels of disease resistances combined with improved color and quality have long made this open-pollinated cultivar a standard slicing cucumber. Decades of cucumber breeding efforts at Cornell have continued to focus on resistance breeding and have generated a series of cucumbers combining disease resistances and other traits, including ‘Marketmore’, ‘Marketmore 70’, ‘Marketmore 76’, ‘Marketmore 87’, and ‘Marketmore 88’. This article highlights the most recent development, ‘Marketmore 97’, and presents data regarding the relative performance of ‘Marketmore 97’ and ‘Marketmore 76’, the most widely grown comparable cultivar.
Resistance breeding in cucumber first began in the United States to address the problem of cucumber mosaic virus (CMV), the most destructive disease of cucumber at that time. Initial crosses to the cultivar ‘White Spine’ were conducted at Cornell University by Oved Shifriss and C.H. Myers using the oriental cultivar Chinese Long, which had been introduced to the United States by R.H. Porter of Iowa State University (Porter, 1929). The largely recessive character of this CMV resistance (Shifriss et al., 1942) was lost during multiple backcross generations. Consequently, early generations relied heavily on the pedigree method (Munger, 1993) (Fig. 1). Crosses were made to several commercially acceptable varieties, self-fed for numerous generations and, to maintain CMV resistance, crossed to an advanced line between ‘Chinese Long’ and several other popular varieties. Scab resistance was introgressed to develop ‘Marketmore’, which quickly gained popularity. A major flaw of this cultivar is that it tends to form light-colored fruit when grown at high temperatures. Introgression of the u gene (Strong, 1930) for uniform fruit color was achieved by backcrossing to the sister line ‘Tablegreen’, resulting in ‘Marketmore 70’.
The prolonged longevity of foliage in the field resulting from CMV and scab resistance resulted in the prominent appearance of mid- to late-season powdery mildew infection. To address this issue, powdery mildew resistance (PMR) from C.E. Peterson's cultivar ‘Spartan Salad’ was added to ‘Marketmore 70’ by backcrossing five times alternating with two generations of self-pollination (Jahn et al., 2002). The resulting cultivar was named ‘Marketmore 76’ and proved to be more widely adapted than earlier versions of ‘Marketmore’. Around this time, it was noticed that the PMR trait of ‘Marketmore 76’ was in an unfavorable linkage with resistance to target leaf spot (Corynespora cassiicola) (Lane and Munger, 1985). Increased resistance to this and several other foliar pathogens was obtained by crossing with ‘Wisconsin 2757’ and backcrossing to ‘Marketmore 76’ to produce ‘Marketmore 87’. Finally, ‘Marketmore 97’ was developed by adding resistance to zucchini yellow mosaic virus (ZYMV), watermelon mosaic virus (WMV), and papaya ringspot virus (PRSV) from ‘Marketmore 88’ (Fig. 1).
Jahn, M., Munger, H. & McCreight, J. 2002 Breeding cucurbit crops for powdery mildew resistance 239 248 Belanger R., Bushnell W., Dik A. & Carver T. The powdery mildews: A comprehensive treatise Amer. Phytopathol. Soc St. Paul, Minn
Lane, D. & Munger, H. 1985 Linkage between Corynespora leafspot resistance and powdery mildew susceptibility in cucumber HortScience 20 593 (abstr.)
Munger, H.M. 1993 Breeding for viral disease resistance in cucurbits 44 60 Kyle M. Resistance to viral diseases of vegetables Timber Press Portland, Ore
Rowell, B., Satanek, A., Slone, D. & Snyder, J. 2002 Yields and gross returns from new slicing cucumber varieties 32 35 2002 Fruit and vegetable crops report University of Kentucky College of Agr Lexington