Exotic Lines Research Articles

Assessment of genetic diversity in Azadirachta indica using AFLP markers

Genetic diversity was estimated in 37 neem accessions from different eco-geographic regions of India and four exotic lines from Thailand using AFLP markers. Seven AFLP selective primer combinations generated a total of 422 amplification products. The average number of scorable fragments was 60 per experiment, and a high degree (69.8%) of polymorphism was obtained per assay with values ranging from 58% to 83.8%. Several rare and accession-specific bands were identified which could be effectively used to distinguish the different genotypes. Genetic relationships within the accessions were evaluated by generating a similarity matrix based on the Jaccard index. The phenetic dendrogram generated by UPGMA as well as principal correspondence analysis separated the 37 Indian genotypes from the four Thai lines. The cluster analysis indicated that neem germplasm within India constitutes a broad genetic base with the values of genetic similarity coefficient ranging from 0.74 to 0.93. Also, the Indian genotypes were more dispersed on the principal correspondence plot, indicating a wide genetic base. The four lines from Thailand, on the other hand, formed a narrow genetic base with similarity coefficients ranging from 0.88 to 0.92. The lowest genetic similarity coefficient value (0.47) was observed between an Indian and an exotic genotype. The level of genetic variation detected within the neem accessions with AFLP analysis suggests that it is an efficient marker technology for delineating genetic relationships amongst genotypes and estimating genetic diversity, thereby enabling the formulation of appropriate strategies for conservation and tree improvement programs.

Effect of nitrate/ammonium ratio on biomass production, nitrogen accumulation, and use efficiency in sorghums of different origin

Plant nitrogen (N) uptake, growth, and N use efficiency may be affected by N form (NO3 ‐or NH4 +) available to the root. The objectives of this study were to determine the effect of mixed N form on dry matter production and partitioning, N uptake, and biomass N use efficiency defined as total dry matter produced per unit plant N (NUE1) in U.S. and tropical grain sorghums [Sorghum bicolor (L.) Moench]. The U.S. derived genotype CK 60 and three tropical genotypes, Malisor‐7, M 35–1, and S 34, were evaluated in a greenhouse trial using three nutrient solutions differing in their NO3 ‐/NH4 + ratio (100/0, 75/25, 50/50). Shoot and root biomass, N accumulation, and NUE, were determined at 10‐leaf and boot stages. Averaged over all genotypes, shoot and root biomass decreased when NH4 + concentration was increased in the solution. Shoot biomass was reduced by 11% for 75/25 and 26% for 50/50 ratios, as compared to 100/0 NO3 ‐/NH4 +. Similarly, root biomass reduction was about 34% and 45% for the same ratios, respectively. Increasing NH4 + concentration also altered biomass partitioning between shoot and root as indicated by decreasing root/shoot ratio. Total plant N content and NUE1 were also reduced by mixed N source. Marked genotypic variability was found for tolerance to higher rates of NH4 +. The tropical line M 35–1 was well adapted to either NO3 ‐ as a sole source, or to an N source containing high amounts of NH4 +. Such a characteristic may exist in some exotic lines and may be used to improve genotypes which do not do well in excessively wet soil conditions where N uptake can be reduced.

Thermal Starch Properties in Corn Belt and Exotic Corn Inbred Lines and Their Crosses

ABSTRACTMore knowledge is needed about variability of starch functional traits in adapted and exotic germplasm and possible genetic effects of these traits before conducting rigorous inheritance studies and breeding programs for starch quality. We studied and compared the range of variability for starch functional traits in a set of Corn Belt inbred lines with a set of exotic inbred lines from Argentina, Uruguay, and South Africa. Reciprocal hybrids of some of the lines within each set were compared with their parents. Functional traits were examined by using differential scanning calorimetry on starch extracted from single kernels of genotypes. The set of Corn Belt lines had a wider range of values for most traits than did the set of exotic lines. For both sets of lines, the maximum value for peak height index was as high as that previously reported for the waxy endosperm mutant. Although the Corn Belt lines exhibited a wider range of values for range of retrogradation than the exotic lines, the exotic lines showed a wider range of values for percentage retrogradation. Hybrid values were not consistently higher, lower, midpoint, or similar with respect to the values of their parents. This was true regardless of germplasm type or functional trait. Reciprocal cross values showed trends suggesting reciprocal differences, although there was no trend suggesting greater effect of the female parent. These traits seem to be controlled by many modifying effects in addition to major effects. Results indicate that sufficient variability exists in Corn Belt germplasm to conduct breeding and inheritance studies effectively and that there should be potential for breeding for functional traits.

Cynodon dactylon: An alternative host for Sporisorium sorghi, the causal organism of sorghum covered smut

Plants of Cynodon dactylon (a weed) showing covered smut symptoms caused by Sporisorium sorghi were collected from fields used for sorghum cultivation. Teliospores from the samples were used to inoculate seeds of 20 sorghum lines before planting. Nineteen of these showed infection of varying intensity. Local lines Mori, Short Kaura (SK 5912), Singe 1 and Singe 2 were heavily smutted, as were the exotic lines ICSV 111, ICSV 554, ICSV 655, IS-9928 and 85-4-BF. ICSV 1002 was highly resistant. This is the first report of C. dactylon being an alternative host of S. sorghi.

Performance of Exotic × Temperate Single‐Cross Maize Hybrids

Maize (Zea mays L.) hybrids were produced by crossing exotic and temperate inbred fines. A total of 12 exotic lines, four from each of three exotic groups (Argentine flint, ETO, and Tuxpeno), were crossed with 16 temperate inbred lines, four from each of four temperate inbred groups (B37, B73, OH43, and MO17). The hybrids were evaluated in 1992 at Leesburg, GA, and Oglethorpe, GA. This study was conducted to identify superior combinations of temperate and exotic heterotic groups. Generally, hybrids with either B73‐derived or Tuxpeno lines had high yield, high grain moisture, high root lodging, and moderate stalk lodging. The B73 × Tuxpeno hybrids had the highest mean yield. Yield of B73 × exotic hybrids was not significantly different from the mean of the checks, whereas the remaining exotic‐temperate combinations had yield significantly less than the checks. Argentine flint lines combined well with B37 and B73 lines, whereas ETO lines produced high yield when crossed with B73 and OH43 lines. Overall, Tuxpeno lines demonstrated higher combining ability with temperate lines than did the Argentine flint or ETO derived lines. Results from this study suggest considerable potential for exploiting exotic germplasm to improve temperate material, especially the MO17 and OH43 derived lines.

Stability of Partial and Complete Resistance in Rice toPyricularia griseaUnder Rainfed Upland Conditions in Eastern Colombia

Two sets of experiments were conducted to compare the relative stability of partial and complete resistance in rice to Pyricularia grisea (causal agent of the rice blast disease) in a disease hot spot in eastern Colombia. In the first set of experiments, 186 breeding lines selected at the site over the F 2 to F 4 generations, ranging from completely to partially resistant in the F 4 , were evaluated under heavy disease pressure at the site every season from 1987 to 1990 (two seasons per year). A set of 92 lines from the International Rice Blast Nursery (IRBN) with initial evaluations of resistant (standard evaluation system [SES] ≤ 5), also ranging from completely to partially resistant, were evaluated under the same conditions. Locally developed materials were rated as susceptible less frequently than lines from the IRBN set. In both sets, significantly fewer lines initially scored as highly resistant (SES = 1 to 3) were later scored as susceptible (SES > 5) or showed any increase in susceptibility to local pathogen populations compared to those initially rated as partially resistant (SES = 4 to 5). In the second set of experiments, locally developed and exotic lines were grouped according to partial (few susceptible-type lesions [SES type 5]) and high resistance (few resistant-type lesions [SES type 1 to 3]). After three seasons of evaluation, lines with high levels of resistance had a significantly lower rate of change to susceptible levels. The rice cultivar Oryzica Llanos 5 was selected at this site from a line with complete blast resistance and was released for commercial cultivation in blast-prone eastern Colombia. It is grown on approximately 5 x 10 4 ha/year and has remained resistant to blast over 10 consecutive growing seasons, both in experimental blast nurseries and in farmers' fields where blast normally is a severe problem. This cultivar also showed uniformly high levels of blast resistance when evaluated at seven high blast level sites in four Asian countries in blast nurseries with 72 other cultivars with differing levels and origins of blast resistance. The results suggest that selecting high levels of resistance when diverse sources are combined can be used to develop cultivars with stable resistance to rice blast.

Introgression of agronomic characters from exotic cowpea germplasm into blackeye bean

Genetic diversity of blackeye bean germplasm ( Vigna unguiculata (L.) Walp.) adapted to irrigated environments is limited. Introgression of exotic germplasm may be necessary for future improvement of agronomic characteristics, but methods for its efficient utilization are not well established. The present study investigated how different sources of exotic germplasm and different proportions of exotic and adapted germplasm affect trait means, genetic variability, and frequency of agronomically acceptable lines. Twenty-eight random lines from each of two adapted-x-exotic crosses were evaluated at each of three levels of introgression (F 2:4, BC 1F 3, and BC 2F 2). These six combinations and the adapted recurrent parent were grown in a replicated experiment at Davis, CA, and evaluated for seed yield, seed size, harvest index, and days to first flower. The recurrent parent was ‘California Blackeye No. 5’. The exotic donor parents (Bush 2 and Bush 5) were of tropical African origin. Seed yields of F 2:4, BC 1F 3, and BC 2F 2 populations were 68%, 85%, and 88%, repectively, of the recurrent parent mean for the Bush 2 population; and 68%, 71%, and 82%, respectively, of the recurrent parent mean for the Bush 5 population. BC 2F 2 populations derived from Bush 2 and Bush 5 retained 67% and 54% of the genetic variability for seed yield exhibited by their respective F 2:4 populations. Genetic variance estimates for most traits were comparable between populations derived from either Bush 2 or Bush 5. Means and range of expression for seed yield were greater for the populations derived from Bush 2. Backcross populations generally had greater genetic variance than would be expected if only additive gene action is assumed and dominance of factors in the exotic lines could partially explain this result. Only the BC 2F 2 populations had any lines with acceptable expression of both seed yield and seed size. Backcross populations were judged to be a superior source of breeding lines with immediate usefulness compared to their single-cross counterparts.

Crossbreeding and selection for fibre traits in cashmere goats

The agricultural industry in the UK is under increasing pressure to diversify its forms of production. One of the potentially most viable options suited to hill and upland farms is the production of cashmere, the fine undercoat produced by down bearing goats. Currently no breed of cashmere goat exists in the U.K. which meets market requirements, however, i.e. large quantities of fine, white cashmere. This paper presents results from a crossbreeding trial with Scottish Feral goats and several exotic lines of cashmere goats, the first step in improving production, and it considers future selection plans for improving cashmere production traits.Cashmere fibre production was evaluated on Scottish Feral goats (F) and on goats imported from Iceland (I), Tasmania (T), New Zealand (N) and Siberia (S), and on two and three way crosses between the F and exotic lines. These goats are owned by a group of commercial farmers, along with the Macaulay Land Use Research Institute, forming a group known as Cashmere Breeders Limited.

Genetic Markers to Locate and Transfer Heterotic Chromosome Blocks for Increased Pearl Millet Yields

The introgression of exotic germplasm by conventional breeding procedures to promote greater heterosis and yield within adapted hybrid cultivars often is a difficult and lengthy process. As part of long‐term investigations, the objectives of this study were to evaluate and use nonlethal genetic markers to locate heterotic chromosome blocks (HCBs) in exotic pearl millet [Pennisetum glaucum (L.) R. Br.] lines, develop methods to use the markers to transfer in the future the selected HCBs to inbred T383, and to increase the yield of ‘Tifleaf 2’ (T85A ✕ T383). The nonlethal dominant R gene for red plant color was used to screen 129 pearl millet near‐isogenic populations for high‐yielding HCBs by measuring height and weight of at least 50 red and 50 green spaced plants in each population. In 27 populations, HCB heterosis [(green — red plant wt)/red plant wt) ✕ 100] ranged from 18 to 61% (P < 0.01). The nonlethal tr gene for the trichomeless condition was used to screen 91 pearl millet populations for HCB heterosis = [(Tr ‐ tr plant wt)/tr plant wt) ✕ 100]. In 52 of these populations, HCB heterosis ranged from 17 to 44% (P < 0.01). The best HCBs are being transferred to inbred T383, the male parent of Tifleaf 2, using the genetic markers R and tr to follow the HCBs during the backcross transfer. The design calls for completing three to four backcross generations per year. When top‐yielding HCBs identified by R and tr become a part of the gene complex of T383, T85A ✕ T383 HCB can be expected to outyield T85A ✕ T383. Plant height measurements were of no value in screening exotic lines for high yielding HCBs.

STUDIES ON PAPAYA PRODUCTION IN MIDDLE GEORGIA

Three exotic lines (Dwarf, L-45, and L-50) of precocious papaya (Carica papaya L.) from India, were grown in nursery rows at the Fort Valley State College Agricultural Research Farm during 1986-1990. Performance of these lines was evaluated for their adaptation and production feasibility under the growing conditions of Middle Georgia. Two lines (L-50 and Dwarf papaya) showed a less satisfactory overall performance than did L-45, which had the highest female to male ratio (7:3) and abundantly produced tree-ripened fruits under cold protection frames during 1989 and 1990. Tree growth and survival for L-45 were greater than those for L-50 and Dwarf papaya lines. Two-month-old greenhouse-grown seedlings when established in the field in April, flowered in 60 to 65 days following transplanting. Under Georgia conditions, fruits ripened on trees in approximately 150 days after fruit set. During 1989-90, the fruit size on L-45 trees varied from 574 g to 2,286 g (mean 1,530 g) with an average of 22.5 fruits per tree. Four years data suggest that papaya can be a successful annual crop if shelter is provided during late fall to protect ripening fruits and trees from frost/cold.

Identification of Sources of Resistance to Common Root Rot in Wheat‐Alien Amphiploid and Chromosome Substitution Lines

Current hard red spring wheat (Triticum aestivum L. em Thell.) cultivars have only a moderate level of resistance to common root rot caused by Cochliobolus sativus (Ito and Knrib.) Dreschl. ex Dastar. The objective of this study was to determine if wheat‐alien amphiploid and chromosome substitution lines derived from Aegilops squarrosa L. and Agropyron species could be used as new sources of root rot resistance. A series of greenhouse studies established that Agrotana, a wheat‐A. trichophorum amphiploid, carried resistance to common root rot. Tests of the chromosome substitution series for the D genome in the winter wheat cultivar Winalta by chromosomes 1 to 7 of Ae. squarrosa demonstrated that the substitutions had no consistent effect on disease severity. Similarly, substitutions of chromosomes 4D, 5D, and 6D of Winalta by homoeologons chromosomes from A. elongatum and chromosome 4B for chromosome 4 from A. intermedium had no effect on root rot severity. Isolations from the subcrown internodeshowed that Agrotana had a significantly lower percentage of plants infected with C. sativus than did other exotic lines and common wheat cultivars, suggesting that it might have a different resistance mechanism against common root rot.

Media and gelling agent effect on cotton callus initiation from excised seed hypocotyls

A factorial experiment was performed to develop a medium which would support initiation and proliferation of callus in a diverse group of exotic lines of Gossypium hirsutum. Seed hypocotyls of T1, T25 and T133 were cultured on Linsmaier and Skoog (LS) basal medium (1965) with NAA or 2,4-D tested in combination with BA or kinetin. The best medium from this study was then compared to five published media for support of callus initiation and growth of the varieties Acala 1517-75, Coker 500, Dunn 120, Paymaster 303 and TM1. Furthermore, the effects of two gelling agents, Difco-Bacto agar and Kelco Gelrite, were investigated with each of the six media. Significantly more callus was initiated on media solidified with Gelrite than with agar. The best callus production occurred on LS medium supplemented with 30gl-1 glucose, 0.1 mgl-1 BA and 0.1 mgl-1 2,4-D.

Resistance of some cotton lines to bacterial blight in Pakistan

Abstract Screening tests carried out at the Central Cotton Research Institute (CCRI), Multan, indicated that 10 exotic cotton lines introduced from the U.S.A. were immune to all the races of Xanthomonas campestris pv. malvacearum (Smith) Dye, present in Pakistan. The immune lines screened in this test appear to be a valuable source of germplasm for the control of the disease in Pakistan.

Genetic variability for grain yield traits of five random-mating populations of Sorghum bicolor (L.) Moench

Abstract Five random-mating sorghum populations were compared with two hybrids to determine amount and range of genetic variability for grain yield and yield components. Populations used represented varied contributions of adapted, temperate lines and converted, tropical exotic lines. Increased levels of genetic variability displayed by populations were generally associated with increases in the proportion of exotic, converted germplasm used in constructing the populations. Based on extent of genetic variability on a per plant basis, TP5R and TP13B offer most potential for improvement of grain yield. Highest variability for grain yield was displayed by TP5R and for seeds per panicle by TP13B. TP5R represented a population composed entirely of diverse converted sorghums. All populations displayed considerable genetic variability for flowering date and plant height, and little genetic variability for panicles per plant. Genetic variability was observed for seed weight in all but one population, TP13B. None of the populations exceeded hybrids for plot grain yield, reflecting the assemblage of desirable genes combined into hybrid combinations compared to the heterogeneous and heterozygous nature of random-mating populations. For the two cropping seasons over which the study was conducted, relative differences between populations and hybrids for grain yield were greater in 1980 than in 1981. Implications for potential improvement of populations with regard to grain yield and breeding needs for sorghum production in semi-arid environments are considered in relation to genetic variability contributed by component lines of populations.

Screening of local and exotic maize lines for stem-borer resistance with special reference to Chilo partellus

After field screening local germplasm for stem-borer ( Chilo partellus , Swin.) resistance for four seasons in two years we identified two sources of resistance, Katumani and Kitale. A cross between them performed better than either of the parents. When exotic lines from CIMMYT, Mexico, reported to be resistant to South and Central American stem-borers were screened at Mbita Point Field Station, to test and confirm their resistance to East African stem-borers, a number of them were found to be resistant to Chilo . It was also noted that the level of their resistance was higher and more broadly based than the local source. This shows that the source of origin is always full of genetic variability. This finding now suggests that a cross between the local and exotic sources should offer a wide scope in the multiple resistance or the multiline approach towards pest management.

Reaction of Peach and Nectarine Cultivars and Selections to Infection by Botryosphaeria dothidea1

Abstract Commercial and exotic cultivars and selections of peach and nectarine [Prunus persica (L.) Batsch] were evaluated for reaction to gummosis caused by Botryosphaeria dothidea (Moug. ex Fr.) Ces & de Not. (B. ribis Gross & Dugg.). Commercial germplasm was susceptible. Mature trees of several exotic lines showed very little natural infection. ‘Eagle Beak’, Plant Introduction (PI) 43289 from China, was the most resistant to gummosis. Artificially inoculated twigs of this line gummed only slightly, although the fungus could still be isolated from some wounds after 16 months.

Maize Streak Virus: I. Host Range and Vulnerability of Maize Germ Plasm

One hundred thirty-eight grass accessions, 529 maize hybrids, inbreds, exotic lines, and sweet corn cultivars, several Sorghum, Tripsacum, and Zea species, and major cereal crop cultivars were tested for susceptibility to maize streak virus disease in both seedling and six- to eight-leaf stages. Fifty-four grass species were symptomatic hosts (verified by back-assays to corn) including 14 annual and 31 perennial hosts not reported previously. All maize lines were susceptible in the seedling stage except Revolution and J-2705, which were highly resistant after the four-leaf stage. Two Tripsacum species and several Tripsacum plant introductions, nursery selections, and exotic Tripsacum collections were susceptible. Although most Zea mays accessions were susceptible, a few collections of Z. mays subsp. parviglumis var. huehuetenangensis from Guatemala were resistant. Cultivars of commonly grown cereal crops varied in susceptibility. Several grass species in the genera Aegilops, Andropogon, Avena, Bothriochloa, Digitaria, Echinochloa, Eleusine, Hyparrhenia, Panicum, Schizachrium, Sorghastrum, Sorghum, Trichachne, Trichloris, and Zea supported abundant oviposition and nymphal development of the vector Cicadulina mbila

INFLUENCE OF RESISTANT AND SUSCEPTIBLE MAIZE INBRED LINES ON THE BIOLOGY OF THE EUROPEAN CORN BORER, OSTRINIA NUBILALIS (LEPIDOPTERA: PYRALIDAE), AFTER NATURAL OVERWINTERING CONDITIONS IN SOUTHWESTERN QUEBEC

AbstractForty exotic maize inbred lines from 10 countries with known resistance or susceptibility to the European corn borer, Ostrinia nubilalis (Hübner), were used to study the effect of plant resistance on borer survival from natural overwintering conditions and particularly the fecundity of the female moth during the following summer. Also, additional information was obtained on different biological characters of the insect. Resistant and susceptible lines were grouped according to their leaf feeding ratings (antibiosis), per cent borer survival at pollination time or at harvest (tolerance). Each specimen observed was kept on the same plant tissue until pupation. The number of eggs and egg masses/female was significantly higher only when lines are grouped according to their leaf feeding ratings. No significant differences were obtained in most biological characters of borers fed on resistant or susceptible maize lines: spring pupation, pupal parasitism, mortality and weight, moth emergence and sex ratio.

Heterosis, combining ability and reciprocal effects for agronomic and chemical characters in sesame

The extent of heterosis was examined for six agronomic and two chemical characters in a complete diallel cross experiment involving a set of ten self-pollinated varieties of sesame (Sesamum indicum L.) of diverse ecogeographic origin. The magnitude of general and specific combining ability variances and differences in reciprocal F 1 hybrids were also investigated.Heterosis was, on average, highest for seed yield (33%), followed by number of capsules per plant (16%). Mean percent heterosis was small for earliness, plant height and number of primary branches, while it was insignificant for number of secondary branches and percentage of oil. Significant negative heterosis was observed for percentage of protein.Percent heterosis was generally higher in Indian x exotic crosses than in Indian x Indian and exotic x exotic crosses. The exotic lines appeared to be useful in Indian sesame breeding programmes, particularly in the improvement of earliness, number of secondary branches, seed yield and protein content.Additive as well as non-additive gene action seemed to govern the expression of the various characters studied. General combining ability variances were predominant for days to flowering, plant height, number of primary branches and number of secondary branches, while specific combining ability variances were in moderate to high proportions for seed yield, percentage of oil and percentage of protein. T.M.V.-2 and S. I. 770 were the best general combiners for many of the characters while S. I. 1783 and Sel-R were found to be the best for earliness and oil content respectively. Significant variances due to reciprocal effects were also detected for some of the characters.Isolation of pure lines was preferred to production of hybrids in sesame, and crossing selected sibs in the early segregating generations followed by inbreeding seemed to be a desirable breeding procedure.

Bird Resistance in Diverse Germplasm of Sorghum1

AbstractThis study was conducted to examine the relative amount of bird resistance present in a broad spectrum of available sorghum [Sorghum bicolor (L.) Moench] since bird resistance is highly desirable for inclusion into plant breeding programs. Ratings were taken on damage inflicted by natural populations of birds and on several plant characters, including tannin content of the seed, color of the seed, and plant height. The bird damage done to 142 domestic and exotic lines of sorghum revealed the presence of germplasm imparting resistance to birds: SPI 35038 had a low damage rating (2.5); lines SA 370 and Colby had a high damage rating (9.0). Some commercially available sorghum hybrids also appeared to have resistance. The amount of tannin in the sorghum seed was negatively associated with bird damage, as were seed color and plant height, although to a lesser extent. The amount of tannin and seed color showed a positive correlation. Nevertheless, several sorghum lines appeared to be resistant that contained a relatively low amount of tannin.