Germinability and desiccation tolerance are important attributes that seeds acquire during their development. The timing in the expression of these characteristics is important to understand how environmental conditions affecting the mother plant influence seed quality. Lettuce plants (cv. Tango) were cultivated in the greenhouse. Seed germination, under light and darkness, was evaluated in fresh and dry seeds at 3, 5, 7, 9, 11, 13, 15, and 17 days after flowering (DAF). Desiccation was performed ≈1 h after harvest by placing the seeds at 25 °C and ≈53% RH. The seed moisture level after desiccation decreased from ∼14% for 3 DAF seed to ∼7% for 7 DAF seed, and then remained constant until the last sampling. Seeds achieved maximum dry weight (physiological maturity) at ∼13 DAF. Germination of fresh seeds increased from 0% at 3DAF to ∼80% at 5 DAF, reaching 100% at 7 DAF. Dry seeds did not germinate when they were 3 or 5 DAF. Seeds at 7 DAF had ∼10% germination and at 9 DAF ∼100%. When germinated in the dark, an increase in germination from 0% in fresh seeds at 3 DAF to 50% germination at 5 DAF was observed. However, seeds at 9 DAF had dark germination values that decreased to 0% and increased again to ∼70% germination at 13 DAF. Dry seeds had no dark germination until 7 DAF, with variable and low germination (below 20%) until 11 DAF, then germination reached a maximum of ∼55% at 13 DAF and decreased to below 10% at 17 DAF. According to these results, lettuce seed germinability and desiccation tolerance were reached sooner than physiological maturity. In the dark, germination of fresh seeds presented a curve with two peaks suggesting that, depending on the seed developmental stage, two different physiological mechanisms restrict dark germination.
Roel Rabara, Samuel Contreras, David Tay, Mark A. Bennett, and Miller B. McDonald
Daniela Farinelli, Pierluigi Pierantozzi, and Assunta Maria Palese
The effect of several pollination combinations of the olive cultivars Ascolana Tenera, Carolea, Leccino, and Picholine on seed quality and seed number and drupe and seed features were evaluated in 2007 and in 2008 in central Italy. The well-known pattern in olive fruit was confirmed by the high percentage of drupes (71.8%, on average) containing one seed with a closed endocarp, as the dispersal unit, optimizing the plant’s investment in seedling survival. Based on the results of the χ2 test of independence, there was a significant maternal and paternal effect on the number of normal seeds per drupe in some years and combinations. Particularly, in 2007, Picholine and Leccino cultivars (as mother) had drupes with two normal seeds (23.7% and 3.1%, respectively, with respect to 10.8% observed in a normal seed pattern), confirming that double-seeding in olive could be cultivar-dependent. Also the specific crosspollination between ‘Carolea’, as a pollenizer, and ‘Ascolana Tenera’ gave rise to a higher proportion of double-seeded drupes in 2007 (39% with respect to 14.3% expected to be in this category). In 2008, although ‘Ascolana Tenera’ produced more drupes with undeveloped seeds (31.9% with respect to 19.7% expected to be in that category), ‘Leccino’ and ‘Carolea’ had drupes with a lower number of undeveloped seed (14.2% and 11.5%, respectively). ‘Maurino’ and ‘Ascolana Tenera’ pollen produced significant effects on ‘Leccino’ drupes by increasing the number of drupes with undeveloped seeds in both experimental years. Double-seeded drupes outweighed those with only one normal seed in ‘Leccino’ and ‘Picholine’. Instead, drupes with undeveloped seeds affected fruit weight, being generally lighter than those with normal seeds. Although the Leccino cultivar, combined with ‘Maurino’ and ‘Ascolana Tenera’, greatly increased the proportion of drupes without normal seed, such condition did not affect their final weight, which was not different from those with one normal seed, suggesting that this variety caused late seed death.
Ahmed R. Aggour and Dermot P. Coyne
Common blight in beans (Phaseolus vulgaris L.) incited by Xanthomonas campestris pv. phaseoli (Smith) Dye (X c p) reduces crop yield and seed quality. The objective of this experiment was to study heritability and phenotypic correlations of the disease reaction to various strains of X c p at several plant developmental stages in specific bean crosses using diverse methods of inoculation. Leaf and pod disease reactions to strains of X c p were inherited quantitatively and narrow-sense heritability estimates were low in the following crosses between Phaseolus vulgaris cultivars/lines: Bac-6 (moderately resistant = MR) × NE-EP1 (MR); Bat-862 (MR) × ‘Pompadour Checa’ (susceptible = S); ‘Pompadour Checa’ (S) × Bac-6 (MR); ‘Venezuela 44’ (S) × Bat-862 (MR). Pod disease reaction was not correlated with leaf disease reaction at any growth stage. Low or nonsignificant phenotypic correlations were detected between disease reactions of leaves at the seedling and flowering stages with the several methods of inoculation. Intermediate phenotypic correlations were found for disease reactions with three methods of inoculation at the seedling stage, but only with two methods in the flowering stage. Negative or nonsignificant phenotypic correlations were observed between leaf disease reaction and number of days to first flower. Different duplicate recessive genes were found to control two foliar abnormality traits: crippled growth and variegated leaves. No plants with a combination of both traits were observed. An association was found between crippled growth and a high level of resistance to strain V3S8 of X c p in the cross Bat-862 × ‘Pompadour Checa’.
Field experiments were conducted in 1996 and 1997 to examine the effects of plant density on yield and quality of fruit and seeds of muskmelons (Cucumis melo L.). Two open-pollinated cultivars, Noy Yizre'el (Ha'Ogen type) and TopMark (western U.S. shipper type), were grown at plant densities ranging from 0.5 to 16.0 plants/m2 under commercial conditions. The highest marketable fruit yields were achieved with plant densities of 2 to 4 plants/m2. In contrast, the highest seed yields were obtained at 8 to 12 plants/m2. Seed yield index [seed yield (g)/fruit yield (kg)] was used as a parameter to define seed production efficiency. High seed yield was closely related to high value of the seed yield index. High seed yield indexes resulted from high plant densities (up to 12 plants/m2), at which the crops produced many, but relatively small fruit. In all cases, the seed yield per fruit (seed number and seed size) increased with increasing fruit weight. However, the sum of the seed yield of two small fruit was always greater than the seed yield of one, double-sized fruit. There was a clear exception with extremely small fruit (<500 g), which produced both low seed yields and poor seed quality. A positive relationship was found between fruit size and seed size in both cultivars. Nevertheless, relatively small seeds (25 to 30 mg) extracted from relatively small fruit (500 to 1000 g) showed the best performance in terms of germination and emergence percentages and rates, and in the vegetative development vigor of the seedlings.
Samuel Contreras, Mark A. Bennett, and David Tay
of seed quality such as germination, germinability, and storability. In general, the consensus is that water deficiency during seed development reduces dormancy and improves germination of wild species ( Fenner, 1991 ; Gutterman, 2000 ; Hilhorst and
Warley M. Nascimento, Jairo V. Vieira, Giovani O. Silva, Kathleen R. Reitsma, and Daniel J. Cantliffe
genetic effects, although the mother-plant environment during seed development and maturation can also affect carrot seed quality ( Gray et al., 1988 ) and influence thermotolerance as observed in other species ( Sung et al., 1998 ). Also, tolerance to
Isabel Pimentel and Samuel Contreras
Lettuce, one of the most important vegetable crops in the world, is established through direct sowing or the transplant of seedlings; in both cases, high seed quality is essential to achieve a successful crop as low or slow germination results in
Charlene M. Grahn, Barbara Hellier, Chris Benedict, and Carol Miles
vigor comprises those properties that determine the potential for rapid, uniform emergence and development of normal seedlings under a wide range of field conditions ( McDonald, 1993 ). Seed vigor is based on seed quality, environmental and maternal
H.J. Hill, Jesse D. Cunningham, Kent J. Bradford, and A.G. Taylor
probit of percent viability after a period of p (days) in storage at a given MC and T (°C), K i is an index of the initial seed quality of the lot, and σ is defined as the standard deviation of individual seed lifespans and varies with storage
Khalid M. Elhindi, Yaser Hassan Dewir, Abdul-Wasea Asrar, Eslam Abdel-Salam, Ahmed Sharaf El-Din, and Mohamed Ali
production of herbs ( Hassan, 2012 ; Pereira, 1992 ; Sajjadi, 2006 ). High seed quality and seedling establishment are the cornerstones of profitable, efficient, and sustainable crop production ( Finch-Savage, 1995 ). Seed dormancy is defined as the failure