Citrullus lanatus (Thunb.) Matsum. & Nakai - Cucurbit Breeding ...

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mosaic (ZYMV). A threatening bacterial disease is bacterial fruit blotch, caused by Acidovorax avenae subsp. citrulli Schaad et al.. Despite the high number of biotic pathogens listed, the genetics of resistance have been described only for the control of Fusarium wilt, gummy stem blight, anthracnose, watermelon mosaic, and zucchini yellow mosaic (Guner and Wehner, 2003; Xu et al., 2004). Seven races of anthracnose have been reported, but races 1, 2, and 3 appear to be the most important in watermelon (Maynard, 2001). Most cultivars are resistant to races 1 and 3, and resistance sources to race 2 have been found, PI 512385 being the most resistant (Boyhan et al., 1994). Resistance to all three races was inherited as a dominant gene in multiple crosses: Ar-1 conferred resistance to races 1 and 3 (Layton, 1937), and Ar-2 1 to race 2 (Winstead et al., 1959). Resistance to three races (0, 1, and 2) of Fusarium wilt has been found and watermelon differentials have been determined. 'Black Diamond' and 'Sugar Baby' are susceptible to all races, 'Quetzali' and 'Mickylee' are resistant to race 0, 'Calhoun Gray' is resistant to races 0 and 1, and PI 296341 and PI 271769 are resistant to all races (Table 1) (Maynard, 2001). In addition, the inheritance of resistance to race 1 has been described. Resistance was inherited as a single dominant gene (Fo-1) in crosses of the resistant 'Calhoun Gray' or 'Summit' with the susceptible 'NH Midget' (Henderson et al., 1970). Resistance to gummy stem blight was found in PI 189225 and PI 271778 and deployed as a single recessive gene (db) to develop the resistant cultivars 'AU-Producer', 'AU-Golden Producer', 'AU-Jubilant', and 'AU-Sweet Scarlet' (Norton, 1979; Norton et al., 1993; Norton et al., 1995; Norton et al., 1986). Nevertheless, these cultivars were less resistant than their resistant parents, thus suggesting a more complex genetics for this trait. Watermelon resistance to viruses has been identified for PRSV, WMV, and ZYMV (Maynard, 2001). So far, identification of two genes for resistance to zucchini yellow mosaic has been reported. Recessive homozygosis at the zym-FL locus was reported to induce resistance to a strain of ZYMV from Florida (Provvidenti, 1991). More recently, resistance to a Chinese strain of the same virus was inherited as the single recessive gene zym-CH (Xu et al., 2004). In addition, Xu et al. (2004) estimated that tolerance to watermelon mosaic in two crosses was controlled by a minimum of two genes with large broad-sense heritability. Finally, one recessive gene (pm) for the susceptibility to powdery mildew was reported (Robinson et al., 9
1975), but no gene has been found for resistance to powdery mildew. The genetics of resistance to this disease is becoming an important information, because powdery mildew is an emerging disease in watermelon. Other genes of minor interest to breeders have been studied and described, as reported in the current watermelon gene list (Guner and Wehner, 2003), such as genes for green flower color (gf), golden leaf color (go), along with several genes coding for specific proteins. On the contrary, watermelon breeders are selecting for many different traits, such as flesh color, rind pattern, plant architecture, leaf shape, and many others and their genetics have not been studied so far. Current efforts are underway to collect mutants by the <strong>Cucurbit</strong> Genetics Cooperative watermelon gene curators (T.C. Wehner and S.R. King). Objectives The objective of this dissertation was to enhance the knowledge of the genetics of the cultivated watermelon, to the benefit of those interested in watermelon improvement. Specifically, we were interested in 1) studying the genetics of rind color and pattern; 2) studying the inheritance of novel skin phenotypes and verifying the genetics of the white, red, salmon yellow and canary yellow flesh colors; 3) establishing the genetic foundations for yield improvement; 4) estimating the heritability and predicted gain from selection for the improvement of fruit-weight; 5) verifying the inheritance of resistance to gummy stem blight; and 6) identifying molecular markers linked to gummy stem blight resistance. Literature Cited Abd el Hafez, A.A., A.K. Gaafer, and A.M.M. Allam. 1981. Inheritance of flesh colour, seed coat cracks and total soluble solids in watermelon and their genetic relations. I. Quantitative traits. Acta Agronomica Academiae Scientiarum Hungaricae. 30: 82-86. Abd el Hafez, A.A., A.K. Gaafer, and A.M.M. Allam. 1985. Inheritance of flesh colour, seed coat cracks and total soluble solids in watermelon and their genetic relations. II. Quantitative characters and the association between various characters. Acta Agronomica Academiae Scientiarum Hungaricae. 34: 84- 89. Boyhan, G., J.D. Norton, and B.R. Abrahams. 1994. Screening for resistance to anthracnose (race 2), gummy stem blight, and root knot nematode in watermelon germplasm. <strong>Cucurbit</strong> Genetics Cooperative Report. 17: 106-110. 10
Page 1 and 2: Abstract GUSMINI, GABRIELE. Inherit
Page 3 and 4: Biography Gabriele Gusmini was born
Page 5 and 6: Currently, Gabriele is planning his
Page 7 and 8: Table of Contents LIST OF TABLES...
Page 9 and 10: Germplasm and Crosses..............
Page 11 and 12: GENERAL INTRODUCTION LIST OF TABLES
Page 13 and 14: GENERAL INTRODUCTION LIST OF FIGURE
Page 15 and 16: HERITABILITY AND GENETIC VARIANCE E
Page 17 and 18: Brief History of Watermelon Breedin
Page 19 and 20: absence of trichomes on the leaves
Page 21 and 22: The genetics of the flesh color in
Page 23: The primary nematode species attack
Page 27 and 28: Henderson, W.R., G.H. Scott, and T.
Page 29 and 30: Shimotsuma, M. 1963. Cytogenetical
Page 31 and 32: Table 1. Watermelon cultivars with
Page 33 and 34: Figure 2. Cultivar Allsweet, releas
Page 35 and 36: Figure 4. Watermelon seeds size: 1
Page 37 and 38: Introduction The inheritance of rin
Page 39 and 40: stripes. In his study, Shimotsuma c
Page 41 and 42: Diamond'), GG mm = mottled dark gre
Page 43 and 44: Shimotsuma, M. 1963. Cytogenetical
Page 45 and 46: Figure 2. Cultivars Japan 6 and Chi
Page 47 and 48: Figure 4. Cultivars Crimson Sweet (
Page 49 and 50: Abstract The watermelon [Citrullus
Page 51 and 52: The rind (skin) colors and patterns
Page 53 and 54: two hybrids are the original canary
Page 55 and 56: Names and symbols for new genes pro
Page 57 and 58: Salmon Yellow and Red Flesh During
Page 59 and 60: During our experiments we did not f
Page 61 and 62: Poole, C.F. and P.C. Grimball. 1945
Page 63 and 64: Table 2. Single locus goodness-of-f
Page 69 and 70: Table 6. Continued. z Generation To
Page 71 and 72: Figure 1. Intermittent stripes in '
Page 73 and 74: Figure 3. Moons and stars induced o
Page 75 and 76:
Figure 5. Examples of unexpected fl
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Abstract High yield is a major goal
Page 79 and 80:
States appears to be narrow, with m
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y using only two replications from
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value=0.0001), indicating that cult
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Levi, A., C.E. Thomas, A.P. Keinath
Page 87 and 88:
Table 1. Analysis of variance (degr
Page 89 and 90:
Table 2. Continued. Yield z Fruit s
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Table 2. Continued. Yield z Fruit s
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w L/D = length/diameter ratio measu
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Abstract The cultivated watermelon
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dominance, and epistatic effects we
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thumped (Maynard, 2001). Weights we
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The giant-fruited parents had a lar
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Literature Cited Brar, J.S. and K.S
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Table 1. Phenotypic variances by ge
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Table 2. Variance and heritability
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t h 2 n = narrow-sense heritability
Page 111 and 112:
Table 3. Continued. Effective Facto
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Figure 1. Each of the three cultiva
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CHAPTER FIVE HERITABILITY AND GENET
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fungus that is seed-borne (Lee et a
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the technique described herein. Pyc
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9 = plant dead. Plants with a disea
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The possible gain from selection pe
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Based on our data, Norton may not h
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Gusmini, G., T.C. Wehner, and G.J.
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Sherbakoff, C.C. 1917. Some importa
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Table 1. Single locus goodness-of-f
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Table 1. Continued. z Generation To
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w Expected was the hypothesized seg
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on leaves only; 5 = some leaves dea
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on leaves only; 5 = some leaves dea
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z Data are ratings from four famili
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CHAPTER SIX PRELIMINARY STUDY OF MO
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fungus that is seed-borne (Lee et a
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approach was successful in assembli
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subculture on artificial medium bas
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We extracted DNA using an extractio
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products using the Genescan ® -500
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(DNA/Polysaccharides) and 260/280 (
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Future Research Based on our prelim
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Gusmini, G., T.L. Ellington, and T.
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Perin, C., L.S. Hagen, V. De Conto,
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Table 2. Analysis of variance for t
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029 v 1 . 3 3 . . 3 4 3 3 . . . + B
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Table 3. Continued. 071 v 1 3 . 3 4
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Table 3. Continued. 113 2 4 5 5 4 3
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Table 3. Continued. 155 2 4 5 4 . 4
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Page 175 and 176:
Page 177 and 178:
Figure 1. Agarose gel electrophores
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1 5 10 15 20 25 30 35 + + + + + + +
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The genetics of rind color (or patt
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were not successful, even though se
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Breeding Methods Traits of interest
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alternative to biotechnology and te
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The solution to these problems is n
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Cucurbit Gene List Committee. 1979.
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Henderson, W.R., G.H. Scott, and T.
Page 195 and 196:
Matthews, P. (ed.). 1993. The guinn
Page 197 and 198:
Provvidenti, R. 1991. Inheritance o
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Souza, F.F.d., M.A.d. Queiroz, and
Page 201:
Wright, S. 1968. The genetics of qu
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