Selection of isoresponsive genotypes in toria (Brassica campestris L.) based on the pattern of response to environmental variations: a proposed method

Summary Thirty-one toria genotypes were compared with three well-established cultivars, Ludhiana Composite-2, K-1 and TCSU-2 (standard testers). The genotypes, which were almost identical to a standard tester in response to environmental variations and which also had other desirable characteristics, were considered to be acceptable for commercial cultivation. Using this criterion, TCSU-7, TH-5 and TH-4 were found to be acceptable for commercial cultivation. TH-4 and TCSU-7 were found superior to TH-5 if r² can be considered as a measure of the agronomical manipulations expected in environmental variations.     

Endogenous abscisic acid and 2-trans-abscisic acid in alternate bearing ‘Wilking’ mandarin trees

The relationship of abscisic acid (ABA) and 2-trans-abscisic acid (t-ABA) to alternate bearing has been examined in Wilking mandarin (Citrus reticulata Blanco) trees. Leaves, stems and buds of trees loaded with fruit (on trees) had 4.3, 6.0 and 2.2 fold higher ABA levels than the corresponding organs from off trees. Leaves had higher ABA levels than stems and buds in both on and off trees. t-ABA was non-detectable in Wilking leaf, stem and bud tissue. Amounts of t-ABA not exceeding 40% of the ABA content, were found in Shamouti and Valencia orange buds and in Wilking fruit peel.The elevated levels of ABA in on tree organs may reflect a stress imposed by the fruit overload.     

Genotype effects on plant regeneration in callus and suspension cultures of Avena

Regenerative potential of the calli of nineteen genotypes of Avena sativa, Avena nuda, Avena byzantina and one interspecific hybrid were compared over three successive cultures. Highly significant genotype and genotype × subculture interactions were observed. Among the highest plant regenerable genotypes were Corbit (first subculture); GAF/Park and 88Ab3073 (second subculture); and GAF/Park and 87Ab5932 (third subculture). These genotypes regenerated on an average 10 to 17 plants each from a 200 mg callus mass after a 30 to 45 proliferation period. GAF/Park, a progeny of an interspecific cross, regenerated plants at a significantly higher level (11.85 plants/rep), followed by the similarly performing A. sativa (6.23 plants) and A. nuda (5.06 plants) genotypes, which were significantly higher than the A. byzantina genotypes (2.07 plants). Four genotypes were tested for their adaptability to suspension culture and plant regeneration potential by separating their cells and cell clusters into two sizes: larger and smaller than 3 mm. Larger clusters yielded plants for three genotypes GAF/Park, 88Ab3073, and Tibor. The smaller clusters only regenerated plants for GAF/Park and 88Ab3073. From one gram of callus used to initiate suspensions of GAF/Park and 88Ab3073, 119.9 and 18.8 plants, respectively, were regenerated. The plants regenerated for various genotypes from agar-solidified or suspension culture experiments had normal growth and seed set. This study confirms high and sustained regenerative capabilities of GAF/Park, a restricted genotype due to the weedy Avena fatua genetic background and identifies alternative genotypes, especially 88Ab3073 for future tissue culture and transformation studies.     

Photoperiodism and thermoperiodism in the predatory mite Amblyseius potentillae are probably based on the same mechanism

Summary A comparative study was made of the photoperiodic and thermoperiodic induction of diapause in the phytoseiid mite Amblyseius potentillae. Sensitivity to thermoperiod was found to be highest during the protonymphal and deutonymphal stages, with some sensitivity still being present in the young adult. Summation of both photoperiodic and thermoperiodic cycles was shown to take place, which demonstrated the presence of a photoperiodic counter as well as a thermoperiodic counter in these mites. Vitamin A appeared to be necessary for some early step in the physiological mechanism of diapause induction and not just for the expression of the diapause response. The light sensitivity threshold for photoperiodic induction of diapause was found to be extremely low, viz. less than 0.02 W/cm². Moreover, the light sensitivity threshold appeared to be strongly temperature dependent in A. potentillae. Experiments in which the mites experienced various sequences of short-day photoperiods and short-day thermoperiods, applied either concurrently or in succession, showed that the information collected by the photoperiodic counter and the thermoperiodic counter is integrated into one induction sum. These results strongly suggest that photoperiodic and thermoperiodic induction of diapause in these mites is based on the same physiological mechanism.Abbreviations DD continuous darkness - LL continuous light - LD light-dark cycle (e.g. LD 16:8 is a cycle of 16 h of light and 8 h of darkness) - TC thermoperiodic cycle (e.g. TC 16:8 (27°: 15°) is a thermoperiod with a 16 h thermophase of 27 °C and an 18 h cryophase of 15°C)     

Genotypic variation in the germination of common bean in response to cold temperature stress

Beans (Phaseolus vulgaris) are regarded as a susceptible crop to suboptimal temperatures. In temperate regions, low temperatures reduce establishment of beans when planted early in the growing season. Seeds of 14 cultivars/lines or beans were germinated in petri dishes at a constant 8, 10, 12, or 18°C or at 12 h alternating temperatures of 10/8, 12/8 or 18/8°C. Differences in germination percentages and rates between cultivars/lines were significant, especially at low temperatures. Cultivars/lines that germinated best and quickly at constant 8°C were Volare, Great Northern (G.N.) Tara, G.N. Belneb # 1, G.N. Spinel, and San Cristobal. Germination percent and rate of Pinto-UI-111 and Canadian Wonder increased significantly when temperatures were increased by 2 to 4°C for 12 h per 24 h, compared with a constant 8°C. Whereas, germination of G.N. Belneb # 1 was reduced. Polyacrylamide gel electrophoresis was used to study the effect of cold treatment on polypeptide patterns of seven cultivars/lines. Seeds were germinated at 18°C constant for 96 h or at 18°C for 48 h followed by 48 h at 2 or 8°C. During cold treatment the synthesis of some polypeptides increased. Volare, G.N. Tara Pinto-UI-111 and Canadian Wonder showed changes in polypeptide patterns, while Alubia-33-1, Michigan 84100 and BAT-1225 showed no changes in polypeptide patterns if compared to the control (96 h at 18°C in the dark). This suggests a likely essential role of these proteins in the development of chilling tolerance.     

Mutagenic effectiveness and efficiency of EMS,DES and gamma-rays in rice

Summary Data on chlorophyll mutation frequency after treatment with EMS, DES and gamma-rays and sequential administration of gamma-rays and the two alkylating agents in three varieties of rice have been used to work out quantitatively the effectiveness and efficiency of each mutagen and combination treatment. For effectiveness, the order is EMS > DES and for efficiency it is EMS > DES > gamma-rays. In some sequential treatments (Gamma-rays + DES in IR8 and Basmati; DES + gamma-rays in IR8 and Jhona; Gamma-rays + EMS in IR8 and Basmati; and EMS + gamma-rays in IR8, Jhona and Basmati) mutation frequency is more than additive (synergistic) but these treatments are decisively less efficient because of their relatively high injurious effects in the M₁. generation. EMS induces more albinas than gamma-rays do. The mutational spectrum patterns induced by gamma-rays and DES are alike. In general, combination treatments tend to increase the frequency of albinas over other types of chlorophyll mutants.     

Genotypic differences in cold tolerance are masked by high sucrose and cytokinin in shoot cultures of sugarbeet

Cold tolerance of field grown plants and shoot cultures of a commercial sugarbeet cultivar, Hilma, was compared with that of two cultivars bred for improved cold tolerance, Monofeb and Winter Hybrid 88619. Leaves of Monofeb and Winter Hybrid 88619 showed an increase in frost tolerance compared to Hilma, as assessed by electrolyte leakage measurements, in both July, and November. However, all varieties exhibited acclimation in the latter month. Similar qualitative differences between cultivars were detected in shoot cultures only when maintained on low (1%) sucrose medium, without added plant growth regulators. The use of high (3%) sucrose and benzyladenine, which releases apical dominance producing multiple shoots, each contributed to a substantial lowering of the temperature at which cold-induced damage occurred in leaves. Under these conditions varietal differences were masked. The implications of these findings in regard to in vitro selection for improved cold tolerance in organized cultures are discussed.Abbreviations BA benzyladenine - MS Murashige & Skoog (1962)     

Improved rate of callus induction from rice anther culture following microscopic staging of microspores in iron alum-haematoxylin

Summary High frequencies of callusing were obtained in indica rice from the microspores which were staged in acetic acid iron alum-haematoxylin stain prior to culture on G5 medium. Two local varieties, Khonorullo and Namyi, and two advance pre-release cultures, PK 1-1-3 and PK 12-22, were used in this investigation. All the cultures exhibited a wide adaptation to varying medium; however, the frequency of callusing was highest (45.5%) in PK 1-1-3 followed by PK 12-22 (32.4%) and Khonorullo (31.6%). Cold shock (10 °C) for 11 days enhanced the frequency of callusing by 200% in Khonorullo.     

Nomenclatural consequences of some recent studies on Brachionus plicatilis (Rotifera,Brachionidae)

Recent studies on morphology, karyotype, genetics including allozyme constitution and reproductive behaviour of S- and L-type B. plicatilis showed that these types are best treated as different species. A reexamination of existing available names revealed B. plicatilis O. F. Müller, 1786 and B. rotundiformis Tschugunoff, 1921 as the correct names for the L- and S-type, respectively.     

Effect of LiCl on compression and tension properties ofPophyra perforata tissue

The mechanical properties of various differentiated regions of thePorphyra perforata thallus and the effect of LiCl were studied by performing compression and tension tests. Among the various differentiated tissues, the holdfast area was high in its compressive modulus of elasticity and tensile modulus of elasticity, possibly related to its thick matrix. Vegetative non-dividing tissue and vegetative dividing tissue were the most flexible and strong, showing the highest percentage elongation at break and tensile strength. The patch area, which is a transition zone leading to sexually mature tissue, had moderate values of tensile properties. Meanwhile, sexually differentiated male and female tissues had the highest compressive modulus of elasticity and lowest tensile properties. Thes tisues tended to crumble easily. Treatments in LiCl, as used for DNA extraction, resulted in a decrease in both compressive modulus of elasticity (87%) and tensile modulus of elasticity (54%). After treatment of tissue for chromosome staining in a method using LiCl, there was a marked decrease in tensile modulus of elasticity (49%), while the compressive modulus of elasticity remained unchanged. Such mechanical changes verify the softening effect of LiCl on the seaweedP. perforata tissue.Author for correspondence     

Genetic analysis of resistance to whitebacked planthopper in twenty-one varieties of rice,Oryza sativa L.

Summary The inheritance of resistance to whitebacked planthopper Sogatella furcifera (Horvath) was studied in 21 rice varieties. Reactions of F₁; F₂ and F₃ progenies of the crosses of 21 resistant varieties with the susceptible variety TN 1 revealed that a single dominant gene governs resistance in Mushkan 41, Santhi, Siahnakidar 195, SM2-34, Tirisurkh 251, Zirijowaian 245, 18, 24A, 39, 76 S, 78, 180, 213 B, 267, 293, CI 6037-4, NP97, S39 JKW and Bansphul. In varieties 65 and 274 A, resistance is governed by one dominant and one recessive gene which segregate independently of each other. Tests for allelism with the Wbph 1 gene originally identified in N 22 revealed that the dominant gene present in all the test varieties is the same as Wbph 1. Further studies are required to determine the allelic relationships of the recessive gene found in varieties 65 and 274 A.     

Are ‘multiple cross-multiple pollen hybrids’ an answer for productive populations in Brassica campestris (var.) Brown Sarson?

Summary A set of 167 mucromphs was evaluated in their F₁ generation for seven plant, four plot and five ratio characters. Methods of characterizing the parents and the hybrids on the basis of combining ability effects described in the first part were found to be efficient in identifying desirable cross combinations for pedigree breeding or generating composite populations. Order effects of multiple-pollen combinations were found to be potent for a number of character components. High x Low cross-combinations were found to produce a high frequency of heterotic crosses followed by High x High. Selected biparental progenies, single crosses, three-way crosses and elite varieties were successful female parents and combinations of pollen from two varieties, one variety and three varieties were successful male parents, in that order, in producing significant heterosis in mucromphs. The relationship between general and specific combining ability on the one hand and realised heterosis on the other was discussed.     

Plant regeneration through culture of isolated microspores of Triticum aestivum L.

Wheat microspores mechanically isolated from the anthers before culture and isolated from the anthers during the hole culture period in a chemically defined medium resulted in proembryos, embryos and finally plants. Of the four genotypes included, all responded with proembryos, and the two spring wheats Ciano and Walter gave rise to macroscopic embryos and plants. The frequency of embryo regeneration and the frequency of albino plants in both Ciano and Walter was in accordance with previously obtained results with anther culture derived material.Abbreviations 2,4-d 2,4-dichlorophenoxy acetic acid - NAA 1-naphthaleneacetic acid     

Sources and inheritance of resistance to leaf curl virus in Lycopersicon

Summary One hundred and twenty-two varieties, lines and wild accessions of Lycopersicon were screened under three different regimes during the autumn/winter season of 1982–83 and 1983–84 for resistance to tomato leaf curl virus (TLCV). L. hirsutum f. glabratum (B6013) and L. hirsutum f. typicum (A1904) proved to be highly resistant to TLCV in all three environments. Various accessions of L. peruvianum were also highly resistant. L. pimpinellifolium (A1921) exhibited no TLCV symptoms within 90 days. Of the cultivated varieties, Acc 99 exhibited the minimim score for susceptibility; AC 142, Collection No. 2, Kalyanpur Angurlata and HS 101 had a low rating for virus incidence. The inheritance of resistance was studied in the interspecific crosses between a TLCV resistant line of L. pimpinellifolium (A1921) and five (HS 101, HS 102, HS 110, Pusa Ruby and Punjab Chhuhara) susceptible cultivars of L. esculentum. Parents, F₁, F₂ and backcross progenies were artificially inoculated with local strains of TLCV using vector the viruliferious whitefly, Bemisia tabaci (Genn.). Data indicated that the resistance of L. pimpinellifolium (A 1921) is monogenic and incompletely dominant over susceptibility.     

Evaluation of an exotic maize population adapted to a locality

Summary An exotic Zea mays L. population (Tuxpeno) was adapted to North Carolina conditions by first introducing genes for adaptability from two North Carolina varieties ([(Jarvis X Indian Chief)Tuxpeno]Tuxpeno) including four generations of intermating, and then selecting for adaptability using maturity as the primary measure. The study evaluated selection for adaptability and the diversity available between adapted Tuxpeno and the local varieties, Jarvis and Indian Chief. Analytical procedures were developed to quantify the diversity between populations and the complementation of local varieties by introduced germ plasms. The analyses utilized the specific effects available from the diallel mating design.Three replicate selections responded similarly under simple recurrent mass selection (1/10) for the earliest disease-free plants initially and additionally for plant types (primarily height) in the final generation. The 1/4 local germ plasm permitted rapid adaptation of Tuxpeno gene pool to local conditions. The adapted Tuxpeno populations yielded similarly to the local populations with an average heterosis for grain yield of 28% when crossed to the local populations used as source of genes for adaptability. The diversity found between adapted Tuxpeno lines and these local varieties based on genes affecting grain yield was 1.5 to 2.5 times that measured between the local varieties (Jarvis and Indian Chief). Diversity lost through intergradation with local material was a reasonable investment. Yield genes introduced from Tuxpeno complemented local gene pools through nonadditive, primarily dominance-associated, gene effects. Reassortment of major gene blocks apparently occurred leading to significant divergence among replicate selections involving both additive-associated and dominance-associated gene effects.Paper No. 6355 of the North Carolina Agri. Res. Ser., Raleigh, NC. Research supported in collaboration with the Rockefeller Foundation and CIMMYT, D.F. (Mexico)     

Variation in the karyotype of three cultivars of Narcissus tazetta L. (Amaryllidaceae)

Three cultivated varieties of Narcissus tazetta, Grand Soleil d'Or, Chinese Sacred Lily and Cypri, are triploid (2n = 3x+30) with the basic number 10. Grand Soleil d'Or has three homomorphic sets, each comprising 2 long submetacentrics, 4 long acrocentrics and 4 short acrocentrics. Karyotypes of the other two varieties are heteromorphic. Both possess one telocentric satellited chromosome. In addition, Cypri shows translocation between two chromosomes belonging to the seventh and eighth triplets. The number of secondary constrictions varies between 3 (Chinese Sacred Lily) and 4 (Grand Soleil d'Or and Cypri) which is also the number of nucleoli observed in the respective varieties.     

Effects of clutch size manipulations on reproductive behaviour and nesting success in the cooperatively breeding Bell Miner (Manorina melanophrys)

Summary An experimental manipulation of clutch size was carried out on a wild population of the cooperatively breeding Bell Miner (Manorina melanophrys, Meliphagidae) to assess which factor(s) limit clutch size in this species. Results provide some support for the trade-off hypothesis since there is a cost of reproduction for the breeding female in terms of loss of body mass. The breeding female performs most of the nestling care. Clutches of three eggs are also laid during the mid-breeding season which is the period most favourable for breeding (i.e. nestlings grow faster). This evidence also supports the intrabrood competition hypothesis. Clutches that have lost an egg were more likely to be deserted; this may be an antipredator strategy since partial clutch predation has been recorded in the field. Nest predation was high in this study (64.9%), suggesting that many small clutches may be a strategy to decrease the effect of nest predation on reproductive success over the whole breeding season (nest predation hypothesis). Both the trade-off hypothesis and the nest predation hypothesis may apply in this case since they are not mutually exclusive. The size of the attending group did not greatly affect reproductive success in the short term, although if both age structure and size of the group are taken into account, reproductive success can be better predicted.     

Identification of a high-molecular-weight subunit of glutenin whose presence correlates with bread-making quality in wheats of related pedigree

Summary The subunit composition of glutenin was analysed by SDS-polyacrylamide-gel electrophoresis using two varieties of contrasting pedigrees. Maris Widgeon, a variety of good bread-making quality, was shown to contain 2 glutenin subunits not present in Maris Ranger, a much higher yielding variety that is unsuitable for making bread. A third subunit was only found in Maris Ranger glutenin. To determine if any of these subunits are directly related to bread-making quality, 60 randomly-derived F₂ progeny from a Maris Widgeon x Maris Ranger cross were analysed for bread-making quality and for glutenin subunit composition. A strong correlation was demonstrated between the presence of one of the two subunits inherited from Maris Widgeon, and quality. This subunit (termed subunit 1 glutenin) had an approx. mol. wt. of 145,000. It was also found in Maris Freeman, a bread-making variety selected from the same cross previously made in 1962. In further crosses involving Maris Widgeon or its descendants, more bread-making varieties have been produced in the last decade at the Plant Breeding Institute, Cambridge and all but one have inherited glutenin subunit 1. The subunit has been traced back through Holdfast to White Fife, a Canadian hard spring wheat of excellent breadmaking quality. Some 67 varieties were screened for the presence of glutenin subunit 1 and it was found in 31% of them. Several unrelated varieties of good bread-making quality did not contain subunit 1 glutenin.     

On morphological variation in Keratella cochlearis populations from Holstein lakes (Northern Germany)

Keratella cochlearis occurs in many Holstein lakes (northern Germany) as three well defined and separated forms: cochlearis, hispida, and tecta, each showing very little variation between the lakes. The present data show that the tecta form did not originate from a Lauterborn cycle.     

Regeneration strategy of mangroves along the Kenya coast: a first approach

In June 1990 a research project sponsored by DANIDA and AWF was carried out by botany students of Nairobi University to investigate the regeneration strategy of mangroves at Gazi bay and Mida creek. Statistical analysis of 449 quadrats (5 × 5 m) sampled along 35 line transects in 4 mangrove forests showed that mangrove seedlings follow the same distribution pattern in the intertidal zone as their parent trees. In other words, mangrove seedlings mainly develop within a well-defined species specific zone. These distribution zones for the various mangrove trees and their seedlings are defined in terms of elevation above the mean low water level of spring tides.Through assigning mangrove seedlings in the intertidal zone to the categories (i) fixed or not-fixed, and (ii) covered or not-covered, evidence was found that propagule dispersal followed both the self-planting theory and the stranding theory. The self-planting theory appeared to be the major mechanism of propagule dispersal in undisturbed mangrove forests, whilst the stranding theory proved to be predominant in colonizing over-exploited and cleared mangrove forests.It is concluded that re-afforestation of mangrove seedlings in the intertidal zone will be most successful when the seedlings are planted in their specific distribution zones under fixed conditions.