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Hongwen Huang, Desmond R. Layne and Thomas L. Kubisiak

Kentucky State Univ. (KSU) is the national clonal germplasm repository for Asimina species. Previous evaluation of the KSU pawpaw collection using 24 isozyme markers demonstrated that pawpaw has a relatively higher genetic diversity than that noted for other plant species with similar species characteristics (long-lived, woody, perennial, out-crossing, temperate, widespread, etc.). Current evaluation using RAPD markers will provide us with a more-accurate insight into pawpaw genetic diversity and population structure. In a preliminary experiment, one hundred 10-mer primers (OA1-20 through OE1-20, Operon Technologies Inc.) were screened against 32 commercial cultivars or advanced selections. A subset of 24 primers that amplify only the most-informative markers were used for germplasm evaluation. Sixty-eight RAPD markers were identified and used for determining genetic parameters. One-hundred-twenty pawpaw accessions were sampled from the KSU repository for RAPD analysis. These accessions represented nine widely distributed states within pawpaw's native range. RAPD data were subjected to various analyses using the NTSYS-PC computer program (ver. 1.8). Information generated from isozyme and RAPD markers will be used to formulate future germplasm collection strategies from wild populations within the native range. The implications of such information to the genetic enhancement of our repository and establishment of a core collection will be discussed.

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Amy Iezzoni

Progress in sour cherry breeding in the U.S. is severely hampered by the limited germplasm available. Importing Prunus germplasm into the U.S. as budwood from the center of diversity in Eastern Europe, is impractical because of the lengthy quarantine period required. Instead it is proposed that pollen collection and the use of a tester clone would be the most efficient way to import and use sour cherry germplasm. Sour cherry pollen can be imported and used directly without a quarantine period. When the pollen is used in crosses with an appropriate tester clone, the breeding value of the germplasm can be assessed relatively easily because both parents are known as opposed to one parent as is the case with open-pollinated seed. Once a germplasm source has been identified as having a desired breeding value, pollen can again be imported or requested from the Plant Introduction Station where presumably the clone is still in quarantine, and used in routine breeding crosses. For a clone to be a good tester, it must induce precocity in the progeny and behave in a recessive manner for traits of importance. Data is presented to illustrate the use of the sour cherry cultivar English Morello as a tester clone for sour cherry germplasm evaluation.

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O.A. Denton Olufolaji, Margaret J. Makinde and J.A. Akinfasoye

Nigeria has diverse ecological conditions, ranging from mangrove swamp of the southern coastal regions to the derived Savannah of the middle belt and the Sudan/Guinea Savannah of the Northern part of the country. Using the southern wet humid rainforest condition of NIHORT, Ibadan, two germplasm evaluation trials were carried out during the rainy season of May to Sept. 1996 and 1997. Thirty-nine tomato accessions were investigated on 1 × 4-m plots at 50 x75-cm spacing in a completely randomized block design with three replications. The top 10 and the least 10 accessions were evaluated for yield in terms of number and weight of both wholesome and unwholesome fruits. In the Northern Guinea Savannah, NHLY-10; Ti 423, and Ti 420 were the best three in terms of fruit number (141 to 117) and weight (673–583 g) per m2. In the northern Sudan Savannah, Ti. 420; NHLY, Äì7 topped the list with (125–72 fruits) and 500–420 g per m2. In the southern rainforest of Ibadan, NHLY, 10; Ti 420, and Ti 423 were superior in fruit number (33–12) and weight (327–150 g/m2 to all the other accessions. However, in the derived Savannah of Ikirun, Ti 423; Roma VF, AND Ti 420 with (85–56 fruits) and(589–278 g) per m2 were quite outstanding among the seven accessions.

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Frank G. Dennis Jr.

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Creighton Gupton and Barbara Smith

Twenty-two muscadine (Vitis rotundifolia) cultivars wars planted in a 4-replication randomized complete block design to 1) accumulate elite germplasm 2) evaluate germplasm and catalog traits that are potentially useful in breeding programs for improving quality and reducing diseases of muscadines consumed as wine, unfermented products, or fresh fruit, and 3) identify cultivars that have acceptable fresh fruit quality. Harvest date ranged from 25 August 92 for 'Southland,' 'Sugargate,' and 'Summit' to 17 September 92 for 'Doreen,' and 'Watergate'. 'Magnolia,' 'Doreen,' 'Janebell,' 'Higgins,' 'Carlos,' and *Welder' produced the highest yields and 'Sugargate,' 'Black Beauty,' 'Fry Seedless,' 'Jumbo,' and 'Sweet Jenny' were the lowest yielding cultivars. The largest berries were produced by 'Black Beauty,' 'Sweet Jenny,' 'Sugargate,' 'Supreme,' and 'Jumbo'. 'Fry Seedless,' 'Nobel,' 'Welder,' 'Doreen,' 'Hunt,' 'Southland,' and 'Sterling' produced the smallest berries. Virtually no ripe rot was found on any cultivar. 'Doreen,' Fry Seedless,' 'Nobel,' 'Supreme,' and 'Welder' were practically free of all disease. The most promising fresh fruit cultivars were 'Supreme,' 'Sweet Jenny,' and 'Black Beauty'.

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Susan C. Miyasaka, Charles E. McCulloch and Scot C. Nelson

Taro leaf blight (TLB), caused by the oomycete pathogen Phytophthora colocasiae, is a worldwide disease that threatens the sustainable cultivation of the tropical root crop taro (Colocasia esculenta). To evaluate taro germplasm from Asia, Hawai‘i, and several South Pacific Islands for resistance to TLB, 119 cultivars were planted along the Hamakua Coast of Hawai‘i (mean annual rainfall of 130 inches) in plots containing five or 10 plants that were replicated over time from 1993 through 2005. Fresh and dry weights of corms were measured after about nine months, with rotten portions removed and weighed. When epidemics of TLB occurred (in nine out of 12 years), visual estimates of disease severity on leaves were assessed using a modified Horsfall–Barratt scale. The correlations between mean dry weight yields for each cultivar and mean severity of TLB, and, respectively, between mean yields and mean severity of corm rots were calculated. As severity of TLB or severity of corm rots increased (suggesting increased susceptibility of particular cultivars to TLB or corm rots), mean dry weight yields decreased significantly (r 2 = 0.37 and 0.22, respectively). “Multiple comparisons with the best” (MCB) were conducted on fresh and dry weight yields, severity of TLB, severity of corm rots, percentage dry matter of corm, and consumer acceptance. Five cultivars were found to be “among the best” with: 1) fresh or dry weight yields that did not differ from the highest level; 2) severity ratings for TLB that were significantly lower than the highest level, suggesting TLB resistance; and 3) percentage of corm rots that were lower than the highest level, suggesting disease resistance. These cultivars, four of which originated from Palau, were Dirratengadik, Merii, Ngesuas, Ochelochel, and Sawa Bastora. Two commercial cultivars from Hawai‘i, Bun Long and Maui Lehua, had fresh and dry weight yields that were significantly lower than the maximum and severity of TLB injury that did not differ from the highest level, indicating that conventional breeding of taro to improve TLB resistance could improve yields of commercial taro cultivars, particularly in areas where epidemics of TLB occur.

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Lisa Alexander

thought ( Dirr, 2009 ). Cold-hardiness of the hybrid fortune’s osmanthus appears to be intermediate to that of its parents ( Dirr, 2009 ), indicating that hybrid breeding may be a promising avenue for improving cold-hardiness in the genus. Germplasm

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Margaret J. Makinde, Adenike O. Olufolahji and Olanrewaju A. Denton

A total of 45 varieties of okra (Abelmoschus esculentus) were evaluated for earliness in fruiting and high fruit yield. In Nigeria selection in okra is for large, spiny fruit with high drawing ability. So far the variety (cultivar) NHAC 47-4 has been well-accepted by both the Nigerian farmers and consumers. It fruit within 42 days and draws and retains fresh color when boiled. These new cultivars, NHAC147 and NHAC 148, were found to fruit within 38 to 40 days and they are of comparable yield of up to 40 fruit per plants. They were found to be drought-tolerant and carry fruit of up to five of same age and size-high degree of uniformity. They are therefore being recommended because they have short stems and NHAC148 has fewer spines than NHAC47-4 AND NHAC 147.

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M.R. Foolad and G.Y. Lin

Cold tolerance (CT) of 31 tomato accessions (cultivars, breeding lines, and plant introductions) representing six Lycopersicon L. sp. was evaluated during seed germination and vegetative growth. Seed germination was evaluated under temperature regimes of 11 ± 0.5 °C (cold stress) and 20 ± 0.5 °C (control) in petri plates containing 0.8% agar medium and maintained in darkness. Cold tolerance during seed germination was defined as the inverse of the ratio of germination time under cold stress to germination time under control conditions and referred to as germination tolerance index (TIG). Across accessions, TIG ranged from 0.15 to 0.48 indicating the presence of genotypic variation for CT during germination. Vegetative growth was evaluated in growth chambers with 12 h days/12 h nights of 12/5 °C (cold stress) and 25/18 °C (control) with a 12 h photoperiod of 350 mmol.m-2.s-1 (photosynthetic photon flux). Cold tolerance during vegetative growth was defined as the ratio of shoot dry weight (DW) under cold stress (DWS) to shoot DW under control (DWC) conditions and referred to as vegetative growth tolerance index (TIVG). Across accessions, TIVG ranged from 0.12 to 0.39 indicating the presence of genotypic variation for CT during vegetative growth. Cold tolerance during vegetative growth was independent of plant vigor, as judged by the absence of a significant correlation (r = 0.14, P > 0.05) between TIVG and DWC. Furthermore, CT during vegetative growth was independent of CT during seed germination, as judged by the absence of a significant rank correlation (rR = 0.14, P > 0.05) between TIVG and TIG. A few accessions, however, were identified with CT during both seed germination and vegetative growth. Results indicate that for CT breeding in tomato, each stage of plant development may have to be evaluated and selected for separately.

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Jessica Chitwood, Ainong Shi, Michael Evans, Curt Rom, Edward E. Gbur Jr., Dennis Motes, Pengyin Chen and David Hensley

Breeding heat-tolerant spinach is an important project to meet the demand of increasing spinach production in heat conditions. Seed germination is the early stage to test, screen, and develop heat-tolerant spinach genotypes. The objective of this research was to determine temperature effect on the seed germination percentage and to select heat-tolerant spinach genotypes. A total of nine spinach genotypes were used in this research. The germination experiment was conducted using seven temperatures: 10, 15, 20, 25, 30, 32, and 35 °C under growth chambers. The temperature trials were conducted using completely randomized design (CRD) with three replicates. Spinach seed germination percentage varied among the nine spinach genotypes under the seven temperatures, indicating that genetic variation for heat tolerance existed in the nine spinach genotypes. ‘Donkey’, ‘Marabu’, and ‘Raccoon’ showed higher seed germination percentage with over 70% at 30 and 32 °C, indicating the three spinach genotypes had heat tolerance for germination. However, all spinach genotypes except ‘Ozarka II’ dropped their germination percentages sharply to less than 30%; ‘Ozarka II’ had 63% germination under 35 °C, indicating it is a good source of heat tolerance for seed germination. The higher germination percentages above 30 °C of ‘Ozarka II’, ‘Donkey’, ‘Marabu’, and ‘Raccoon’ may indicate their potential as donors of heat-tolerant traits in spinach breeding program.