Evaluation of Brassica genotypes for resistance to shatter. II. Variation in siliqua strengh within and between accessions

Summary Within-plant variation in strength of the siliquae, studied in seven Brassica accessions, appears to be mostly associated with variation in size, rather than the position of the siliquae in the infructescence. Position and strength did not show correlated variation in three accessions where the position of the siliqua in the infructescence appeared to significantly influence its strength (adjusted for the effect of size). There was significant variation in strength between plants within accessions. Considering the above results, variation between siliquae from the same accession could be reduced by sampling siliquae of average size as represented by length. When comparing accessions, a few siliquae from many plants would provide a more representative sample than many siliquae from few plants. Use of strength measures adjusted for the size of the siliquae (bending moment/length² and energy/length) would enhance the accuracy of estimation of inherent shatter-resistance. A minimum of three to six tests per accession appeared to be necessary for satisfactory evaluation of shatter-resistance.     

Inheritance of siliqua locule number and seed coat colour in Brassica juncea

The inheritance of siliqua locule number and seed coat colour in Brassica juncea was investigated, using three lines each of tetralocular brown seeded and bilocular yellow seeded. Three crosses of tetralocular brown seeded × bilocular yellow seeded lines were attempted and their F₁, F₂ and backcross generations were examined for segregation of these two traits. Brown seed colour and bilocular siliqua characters were found to be dominant over yellow seed and tetralocular siliqua, respectively. Chi‐square tests indicated that each trait is controlled by different sets of duplicate pairs of genes. Bilocular siliquae or brown seeds can result from the presence of either of two dominant alleles, whereas tetralocular siliquae or yellow seeds are produced when alleles at both loci are recessive. A joint segregation analysis of F₂ data indicated that the genes governing siliqua locule number and seed colour were inherited independently.     

The inheritance of partial self-compatibility in Brassica oleracea L.: Results from a half diallel homozygous for a moderately recessive S-allele

Summary In a study of partial self-compatibility in Brassica oleracea, flower number, seeded siliqua and seed production were recorded on self-and cross-pollinated inflorescences of the progenies of a half diallel between six in bred Brussels sprout plants homozygous for the same moderately recessive incompatibility allele S₄₅.On both self-and cross-pollinated inflorescences significant amounts of additively controlled genetic variation were found for seed set per flower. For cross-pollinated inflorescences this was also the case for the two components of seed set, seeded siliquae per flower and seeds per seeded siliquae, but for self-pollinated ones only seeded siliquae production showed significant additive variation. Considerable heterosis and gene interaction were always present and a simple additive dominance model did not explain the variation.Two of the parents transmitted lower levels of partial self-compatibility to their progenies and, in one of these, dominant genes appeared to be responsible. The most important feature determining the production of self seeds was found to be the number of flowering sites at which the incompatibility mechanism failed rather than the number of seeds produced at each site.     

Salt-tolerance in Brassica juncea L. II. Salt-stress induced changes in polypeptide pattern of in vitro selected NaCl-tolerant plants

Summary The effect of salt-stress was studied on SDS-PAGE pattern of polypeptides in seedling, leaf and siliqua tissues of four genetically stable lines (SR2P1-2, SR3P2-1, SR3P6-1 and SR3P6-2) of in vitro selected NaCl-tolerant plants, a non-selected somaclone (CP5-2) and parent variety Prakash of Brassica juncea L. Seedlings were raised in 0, 50, 100 and 150 meq/l NaCl solutions and plants were irrigated with nutrient solution with 0, 30, 60 & 90 meq/l NaCl. Salinity induced distinct genotype specific changes in polypeptide pattern of leaf and siliqua tissues, while it had no effect on the polypeptide pattern of seedlings, radicle or hypocotyl tissues in any of the lines. In leaves, at vegetative stage, a high molecular weight protein of 53.2 kD while disappered at 60 mM and higher NaCl level in cv. Prakash and SR3P2-1, it appeared in SR2P1-2 and CP5-2 only at these higher salt levels and in SR3P6 lines it was present irrespective of stress conditions. Differences were also observed for a 93.8 kD protein which appeared anew under stress in cv. Prakash, CP5-2 and SR2P1-2, while it was absent in SR-3 lines. Intensity of the 57.3 kD protein decreased in cv. Prakash, increased in SR-2 and CP-5 lines whereas remained unchanged in SR-3 lines under salt-stress. In siliquae, salt stress induced the expression of four new polypeptides (56.1–70.8 kD) at 60 mM NaCl in cv. Prakash, and at 30 mM in SR2P1-2, SR3P2-1 and SR3P6-1 lines, while these were present in CP5-2 and SR3P6-2 even in the absence of NaCl stress.     

Inheritance of siliqua characters in Indian colza I. Locule number and siliqua position

Summary F₁, F₂, BC₁ and BC₂ generations, involving bilocular and tetralocular siliquae and with upright and pendent siliqua position, were studied with their parents. The segregation pattern in these generations indicated that number of locules is monogenically governed with the allel for bilocular type (VV-two valved pods) showing complete dominance over tetralocular (vv). Upright siliqua position is governed by two dominant genes (Up₁ Up₁ Up₂ Up₂) and pendent by two recessive genes (up₁ up₁ up₂ up₂). However, in absence of even a single dominant gene it give rise to a third type of siliqua position i.e. parallel.     

Cytogenetics of Brassica juncea×Brassica rapa hybrids and patterns of variation in the hybrid derivatives

Interspecific hybridization is an important tool to elucidate intergenomic relationships, transfer characters across species and develop synthetic amphidiploids, and it has been widely applied for improving Brassicas. The objective of the present study was to create genetic variability in Brassica through interspecific hybridization. Crosses between Brassica juncea (AABB, 2n= 36), and Brassica rapa (AA, 2n = 20) vars toria, yellow sarson, and brown sarson were attempted, and the hybrid derivatives were advanced to the F4 generation. Hybrids were obtained from the crosses B. juncea× toria and B. juncea× yellow sarson. The F₁ plants were vigorous and intermediate to the parents in many morphological traits. The meiotic study of AAB hybrids showed 10 II + 8 I in the majority (71.8%) of cells analysed. A maximum of 12 and a minimum of seven bivalents were also observed in a few cells. The occurrence of multivalent associations (trivalents to pentavalents) at diakinesis/metaphase I and a bridge‐fragment configuration at anaphase I were attributed to homoeology between A and B genomes. A high percentage of plants resembling B. juncea was observed in the F₂ generation. Transgressive segregation in both directions was found for plant height, primary branches, main raceme length, siliquae on main raceme, siliqua intensity, seeds per siliqua and seed yield. There were significant differences for the 14 characters in the F₄ derivatives. Moderate to high estimates of phenotypic and genotypic coefficients of variation, broad‐sense heritability, and expected genetic advance were found for seed yield, 1000‐seed weight, siliquae per plant, seeds per siliqua and days to flowering. Intergenomic recombination, reflected as wide variation in the hybrid progenies, permitted the selection of some useful derivatives.     

Influence of timing of cross-versus self-pollination on self-incompatibility in Brussels sprout inbreds

Summary The impact of cross pollination 30 h, 4 h, and immediately prior to self-pollination, and self-pollination 2, 4, 8, 12, 24 and 30 h prior to cross-pollination was assessed for pollen tube number per style, seed number per siliqua, and proportion of self-seed (sibs) per siliqua, in two inbred lines of brussels sprout. Pollination procedure had a marked effect on the amount of sib-and hybrid seed produced. Cross pollination 30 h prior to self-pollination produced significantly greater numbers of sib progeny, as did self-pollination 8–12 h before cross pollination. Prior application of self pollen reduces the number of pollen tubes in the style. The results of this experiment suggest that self-incompatibility in brussels sprout could better be assessed by self-pollination with a subsequent cross pollination 8 h later, and the determination of amounts of sib and F₁ hybrid seed per siliqua.     

Untersuchungen zum Einfluß der Bestandesdichte auf das Ertragspotential von Rapspflanzen (Brassica napus L. var. napus)*)

Investigations on the effect of number of plants/area on the yield potential of rapeseed plants (Brassica napus L. var. napus) Based on field experiments with winter rapeseed, the effect of number of plants per area on yield potential and components of yield were investigated. The dependence of yield from number of plants per area before and after winter was analyzed by manipulating the number of plants immediately after sowing and in spring before beginning of growth. The number of plants per area was varied between 10 plants/m² till 185 plants/m². The results show that the yield potential is partly dependend on the growing conditions before winter as influenced by the number of plants per area; the yield potential declines with increasing number of plants/area before winter; affected are the number of siliquae producing lateral shoots, the number of siliquae per shoot and seeds per siliqua. The growing conditions before winter, in this way control the capacity of the rapeseed plant to utilize environmental factors in the main growing period. 50–100 plants/m² before winter and 45–90 plants/m² after winter are within the compensation capacity of rapeseed plants.     

Resynthesizing <Emphasis Type="Italic">Brassica napus</Emphasis> from interspecific hybridization between <Emphasis Type="Italic">Brassica rapa</Emphasis> and <Emphasis Type="Italic">B. oleracea</Emphasis> through ovary culture

Using three varieties of Brassica rapa, cv. Hauarad (accession 708), cv. Maoshan-3 (714) and cv. Youbai (715), as the maternal plants and one variety of B. oleracea cv. Jingfeng-1 (6012) as the paternal plant, crosses were made to produce interspecific hybrids through ovary culture techniques. A better response of seed formation was observed when ovaries were cultured in vitro at 9–12 days after pollination on the basal MS and B5 media supplemented with 6-benzylaminopurine (BA) and naphthylacetic acid (NAA). The best response was observed for cross 714×6012 with the rate of seeds per ovary reaching 43.0%. Seeds for cross 715×6012 showed the best germination response (66.7%) on the regeneration medium (MS+1.0 mg l^–1 BA+0.05 mg l^–1 NAA). In all three cross combinations, good response in terms of root number and length of plants was observed on the root induction medium (MS+1.0 mg l^–1 BA+0.1 mg l^–1 NAA). A better response was observed for the regenerated plants cultured for 14 days than for 7 days. The ovary-derived plants with well-developed root system were hardened for 8 days and their survival rate reached over 80%. Cytological studies showed that the chromosome number of all plants tested was 19 (the sum of both parents), indicating that these regenerated plants were all true hybrids of B. rapa (n = 10) × B. oleracea (n = 9). The regenerated plants were doubled with colchicine treatment, and the best response in the crosses 708×6012, 714×6012 and 715×6012 was observed when treated with 170 mg l^–1 colchicine for up to 30 h and their doubling frequency reached 52, 56 and 62%, respectively.     

Image analysis measurements and repeatability estimates of siliqua morphological traits in Brassica campestris L

Summary The repeatabilities of six traits; peduncle, pod, beak, and total siliqua length, seed number/siliqua and seed mass/siliqua were estimated for the random-mating CrGC-1 Brassica campestris L. population. All length measurements were made using a fast digital image analysis technique. Beak, pod, and total siliqua length showed the highest repeatabilities of all six traits (0.73, 0.63, and 0.63, respectively). Both pod and total siliqua length were highly correlated with both seed number and seed mass/siliqua. These results suggest that these siliqua-related morphological traits could be used as indirect indices of selection in breeding for improved seed yields in Brassica campestris L.     

Identification of RAPD markers linked to recessive genes conferring siliqua shatter resistance in Brassica rapa

Shattering of siliquae causes significant seed loss in canola (Brassica napus) production worldwide. There is little genetic variation for resistance to shatter in canola and, hence, the trait has been studied in B. rapa. Previous studies have shown two randomly segregating recessive genes to be responsible for shatter resistance. Three random amplified polymorphic DNA markers were identified as being linked to shatter resistance using bulked segregant analysis in a F₃B. rapa population. The population was derived from a cross between a shatter‐susceptible Canadian cultivar and a shatter‐resistant Indian line. Of the three markers, RAC‐3₉₀₀ and RX‐7₁₀₀₀ were linked to recessive sh1 and sh2 alleles, and SAC‐20₁₃₀₀ was linked to both dominant Sh1 and Sh2 alleles. The common marker for the dominant wild‐type allele for the two loci was explained to have resulted from duplication of an original locus and the associated markers through chromosome duplication and rearrangements in the process of evolution of the modern B. rapa from its progenitor that had a lower number of chromosomes. Segregation data from double heterozygous F₃ families, although limited, indicated the markers were not linked to each other and provided further evidence for the duplication hypothesis.     

Regenerative trait and cold hardiness in highly productive cultivars of alfalfa and red clover

Summary In earlier work on improvement of persistance in forage legumes, we selected genotypes from highly productive cultivars of alfalfa, Algonquin and Apica (Euphytica 45: 105–112, 1990) and cv. Florex red clover (Plant Cell Reports 8: 395–398, 1989) capable of in vitro regeneration from callus and cell culture. The alfalfa germplasm and its F₁ progeny as well as an F₂ red clover population were tested for cold stress tolerance. Plantlets were hardened in culture tubes at 2 or 5°C, 8h photoperiod, for at least four weeks and then subjected to freezing temperatures, –16 or –10°C for alfalfa and red clover, respectively. Survival of regenerative genotypes was significantly higher than of the non-regenerative ones in both species. A strong oositive correlation (r=0.78) between the regenerative trait and plant survival was found in alfalfa. The experiments indicate that in vitro selection for regenerative trait may improve cold stress tolerance of alfalfa and red clover.     

An intersubgeneric hybrid between Glycine tomentella Hayata and the soybean,G. max (L.) Merr.

Summary The objective of the present paper is to provide information on the morphology and cytology of an intersub-generic hybrid (2n=59) between Glycine tomentella Hayata (2n=78) and G. max (L.) Merr. (2n=40) obtained through in vitro immature seed culture. The hybrid plant was slow in vegetative growth and twinning like the female parent but morphologically was intermediate between both parents for several traits. At metaphase I, the average chromosome associations and ranges for 25 cells were 44.0 I (37–51)+7.5 II (3–11). The plant was completely pollen and seed sterile. The present investigation suggests that wild perennial Glycine species can be exploited as either the male or female parent in wide hybridization programs with the soybean, G. max.     

Coagulable protein in potato: Screening method and prospects for breeding

Summary From tubers of 34 varieties of Solanum tuberosum, extracts were prepared and analysed for crude protein and coagulable protein by the Kjeldahl method. Content of coagulable protein was 0.37–1.24%. From the same material, juice was prepared with a juice centrifuge and analysed for coagulable protein by the Kjeldahl and microbiuret method. The average amount of coagulable protein in the juice was 81.8% of the total coagulable protein. The correlation coefficient between coagulable protein in the juice and total coagulable protein was 0.956. The correlation coefficient between Kjeldahl and microbiuret data for coagulable protein in the juice was 0.956. Analysis of tuber juice by the microbiuret method is recommended as a rapid screening technique for coagulable protein.Relationships between protein data of the 34 varieties and earliness, yield and content of dry matter were analysed statistically. Content of coagulable protein in fresh material correlated with content of dry matter (rs=–0.756), yield of fresh potatoes (r=–0.615) and earliness (r=–0.361) but not significantly with yield of dry matter (rs=–0.309). Coagulable protein in dry matter correlated with fresh yield (r=–0.525), but not significantly with content of dry matter (r=–0.260), yield of dry matter (r=–0.131) and earliness (r=–0.054). Path coefficient analysis showed that 67% of the variation in coagulable protein in fresh material was statistically determined by earliness, content of dry matter, fresh yield and content of uncoagulable protein in fresh material, whereas only 34% of the variation in content of coagulable protein in dry matter was determined by these components. A high content of coagulable protein in fresh or dry matter can be combined with early maturity and with high yield of dry matter. Coagulable protein in dry matter seems to be a more suitable criterion of selection than coagulable protein in fresh material.     

Pod shatter resistance evaluation in cultivars and breeding lines of Brassica napus, B. juncea and Sinapis alba

Pod shatter susceptibility was investigated in Brassica napus germplasm and shatter resistant species of B. juncea and Sinapis alba. The comparisons were made by measuring seed yield in field plots, detached pod rupture energy (RE) and the half‐life of pod‐opening. Pod shatter resistance was significantly greater in B. napus lines derived from interspecific hybridizations of B. napus with B. rapa, B. carinata and B. juncea, than common B. napus cultivars. While these lines exhibited no significant difference in resistance to pod shatter than B. juncea, an entry of S. alba had no yield loss caused by pod shatter. Resistance to pod shatter was characterized in the field as little or no yield loss after full maturity, delayed shattering in time, and stable yield performance under variable climatic conditions during pod maturity. Yield loss caused by pod shatter ranged from a low of 4% for the B. juncea cv. ‘AC Vulcan’ to a high of 61% for the black seeded B. napus line DH12075 in 2‐year field trials after 1 month maturity. Pod shatter resistance was not significantly associated with specific plant and pod morphological traits, except pod length (P = 0.005) in tested materials. Field visual scores of pod shatter through inspections of average pod shatter per plant within plots were highly correlated with plot yield loss. Indoor quantitative evaluations of pod strength using a pendulum machine to measure pod RE and random impact test to measure half‐life of pod‐opening resistance were highly correlated with field yield loss. Multiple evaluations of pod shatter in method and in time after pod maturity are recommended for reliable evaluation of pod shatter resistance.     

Intraspecific hybridization in Pinus caribaea var. hondurensis II. Genetic parameters

Genetic parameters of growth and stemstraightness to seven years of age wereestimated from two field populations ofpure Pinus caribaea var. hondurensis provenances and theirintraspecific hybrids, (Mountain Pine Ridge(MPR) × coastal provenances). There were noconsistent differences in the geneticparameter estimates obtained for theparental provenances compared to those fromthe MPR × coastal inter-provenance hybridcrosses. Narrow-sense heritabilities ofgrowth traits (0.06–0.33) andstraightness (0.21–0.50) were within therange of estimates that have beenpreviously reported for this species andother tropical pines. In general, additivevariance was found to be more importantthan dominance variance for growth andstraightness traits. There was no strongevidence to affirm that the superiority ofthe MPR × coastal hybrid could be caused bydominance variance. The low magnitude ofthe type-B genetic correlations within theMPR × coastal hybrid crosses suggested thatthe genotype-by-environment interactionmight be of practical importance inbreeding. For future hybridization of theMPR and coastal provenances, a recurrentselection scheme based on the utilizationof additive genetic variance of both parentpopulations is recommended.     

Evaluation of the U.S. cucumber germplasm collection for root size using a subjective rating technique

Summary Root size in cucumber (Cucumis sativus L.) has received little research attention until recently. However, a large root system could improve nutrient and water uptake, and ultimately yield. Knowledge of root size could help cucumber breeders develop cultivars with improved performance. A study was conducted in the greenhouse to evaluate 857 cultigens (827 plant introduction accessions, 22 breeding lines, and 8 cultivars) of cucumber for root length. Complete data were obtained for 794 cultigens. Plants were grown from seeds in 2 replications in the greenhouse. Plants were rated for root length using a 1 to 9 scale (1–3 = small, 4–6 = medium 7–9 = large). Also, root length was measured from soil surface to the tip of the longest main root. In addition, all cultigens were evaluated for root length and dry weight to provide meaning to the subjective rating. Root rating was highly correlated with both root length (r=0.92) and dry weight (r=0.64) of roots. Root length averaged 74 mm and most cultigens (579, or 68%) had roots 40 to 110 mm long. The cultigen with the longest roots was PI 183056 (193 mm), and the shortest was PI 176954 (2 mm). The subjective rating technique provided a simple, accurate and rapid method to estimate root growth in the greenhouse.     

Partial control of chromosome elimination by temperature in immature embryos of Hordeum vulgare L. x H. bulbosum L.

Summary Embryos derived from Hordeum vulgare L. x H. bulbosum L. were subjected in vivo to a range of temperatures, and the proportions of hybrid plants which retain both parental sets of chromosomes were determined. Elimination of the H. bulbosum genome was significantly increased at temperatures greater than 20°C and resulted in fewer hybrid plants compared with temperatures below 17.5°C. Embryos were also allowed to develop in situ at 15°C and then transferred to 26°C for 8, 16 or 24h during the first 7 days after pollination. A period of 16 h at 26°C (equivalent to at least one complete mitotic cycle) at 2–5 days after pollination was found to be sufficient to increase chromosome elimination significantly above the levels obtained at a constant 15°C. At this stage (2–5 days after pollination at 15°C) the mean embryonic cell number was 2.3–223.     

Relationship of plant height and days to maturity with resistance to spot blotch in wheat

A total of 1,407 spring wheat (T. aestivum) lines of Indian and CIMMYT (International Maize and Wheat Improvement Centre, Mexico) origin were evaluated for plant height, days to maturity and resistance to spot blotch (caused by Bipolaris sorokiniana) during the 1994–95, 1995–96 and 1996–97 crop seasons. The frequency distribution of genotypes, based on disease score ignoring the growth stages, differed from the distribution in which disease score was assessed on a similar growth stage. Two crosses each,between `tall resistant × dwarf susceptible' and `late resistant × early susceptible' genotypes, were made. The evaluation of homozygous resistant lines in the F₃, F₄ and F₅ generations of both crosses showed a wide range of plant height and days to maturity. These lines showed significant differences for plant height and days to maturity but did not show a significant difference for AUDPC values of spot blotch. The correlation coefficients for AUDPC versus plant height or days to maturity were weak, i.e., – 0.336 and 0.061, respectively. Results indicated that resistance to spot blotch severity was independent of plant height and days to maturity in progenies from these crosses.     

Evaluation of a DNA probe for the quantitative detection of common bacterial blight in common bean and its application in a breeding program

Summary Breeding of Phaseolus vulgaris L. for resistance to common bacterial blight (CBB) can be done with visual evaluations of symptoms to distinguish broad resistance classes, but a more quantitative measure was needed for genetic studies of resistance. A novel method of evaluation was developed by quantifying Xanthomonas campestris pv. phaseoli (XCP) in bean leaf tissue infected with CBB using a ³²P-labeled probe and densitometric analysis of hybridization signals. Quantification of bacterial populations using the probe was highly correlated (r=0.98) with the number of colony forming units (CFU) from plate counts of the same leaf samples. The probe was used to follow XCP population dynamics on susceptible (BAT 41) and resistant (OAC 88-1) bean genotypes. OAC 88-1 supported a maximum XCP population which was approximately tenfold less than BAT 41. The probe was also used to study an F₂/F₃ population segregating for resistance. Narrow sense heritability estimates were less for resistance measured on the basis of bacterial populations (0.18–0.26) than on visual scores of symptoms (0.29–0.38). The anticipated response to selection for CBB resistance would be less based on bacterial numbers than based on symptom expression in this population. In breeding for resistance to CBB, selection based on visual symptoms combined with measurements of XCP populations using a DNA probe can be used to develop bean genotypes that are both resistant to symptom development and bacterial multiplication.Abbreviations CBB common bacterial blight - CFU colony forming units - XCP Xanthomonas campestris pv. phaseoli