Susceptible Commercial Cultivar Research Articles

Effect of host plant resistance and chemical control of the head bug, Calocoris angustatus Leth., on grain quality and seedling establishment in sorghum

SummaryThe sorghum head bug, Calocoris angustatus Lethiery (Hemiptera: Miridae), is one of the most important pests of grain sorghum in India. Studies were conducted to quantify the effect of head bug damage on grain quality and seedling establishment on head bug‐resistant cultivars (IS 17610 and IS 21443), a moderately susceptible cultivar (IS 9692), and a susceptible commercial cultivar (CSH 11). Differences in 1000‐grain mass, seed germination and percentage of floaters were significant between protected and unprotected plots in CSH 11 and IS 9692, but not in IS 17610 and IS 21443. Grain damage ratings were significantly lower in IS 17610 than in IS 9692 and CSH 11 across different protection levels.Head bug‐damaged grain had greater protein content than the undamaged grain, possibly because of depletion in starch, and a marginal increase in soluble sugars. Amounts of proline and tyrosine were greater in the bug‐damaged grain than in the undamaged grain, while the reverse was true for aspartic acid, methionine, leucine and lysine. Head bug damage also increased the tannin content in IS 9692 (which is a high‐tannin genotype).Moisture regimes and insecticide protection levels significantly affected seedling emergence. Seedling emergence of CSH 11 was lower than that in IS 17610. In the latter genotype, the differences between protected and unprotected plots were not significant. Head bug damage thus not only leads to quantitative loss in grain yield, but also spoils the grain quality and renders the grain unfit for seed purposes. These qualitative effects should be taken into account while estimating losses due to bug damage and determining economic thresholds.

Characterization of Resistance to Limabean Pod Borer (Lepidoptera: Pyralidae) in Soybean

In four tests conducted in summer through autumn 1987, soybean, Glycine max (L.) Merrill, accession PI 227687 was consistently less damaged than the susceptible controls by the limabean pod borer, Etiella zinckenella (Trietsche). Damage by pod borers increased with increasing trichome density on pods. Seed size was not a decisive factor in pod borer damage in the resistant accession. Limabean pod borer laid significantly fewer eggs on PI 227687 plants than on ‘KS 9’ plants, a susceptible commercial cultivar. Significantly fewer larvae entered the pods of PI 227687 to feed on developing seeds than in the pods of ‘KS 9’. Pupation was reduced when larvae were fed on PI 227687 compared with ‘KS 9’. Pupae were significantly lighter in weight and the percentage successfully emerging into adults was Significantly lower when larvae were fed on PI 227687 rather than on ‘KS 9’. Oviposition nonpreference and antibiosis appeared to be the mechanisms of limabean pod borer resistance in PI 227687.

Field evaluation of insect resistance in a wild tomato and its effects on insect parasitoids

AbstractPopulations of Helicoverpa (= Heliothis) zea (Boddie), Heliothis virescens (F.), Manduca sexta (L.) and M. quinquemaculata (Haw.) and their egg and larval parasitoids were sampled in field plots of the: insect‐resistant wild tomato, Lycopersicon hirsutum f. glabratum C. H. Mull, accession PI 134417; susceptible commercial tomato cultivar ‘Better Boy’ F1 hybrid; and selected, moderately resistant backcross genotype. Densities of H. zea and H. virescens eggs and small larvae were higher on resistant genotypes than on susceptible genotypes, but densities of large larvae were similar on all genotypes. Densities of Manduca spp. larvae were too low to permit similar analyses of the effects of plant genotype. Rates of egg parasitism by Trichogramma spp. and Telenomus sphingis (Ashmead) were reduced on insect‐resistant genotypes. Rates of parasitism by the larval parasitoids Campoletis sonorensis (Cameron) and Cotesia congregata (Say) were reduced on resistant genotypes. No consistent effects on parasitism rates by Cotesia marginiventris (Cresson) were observed and parasitism rates by Cardiochiles nigriceps Viereck were unaffected.

Components of Partial Resistance to Blue Mold in Six Tobacco Genotypes Under Controlled Environmental Conditions

Rufty, R. C., and Main, C. E. 1989. Components of partial resistance to blue mold in six tobacco genotypes under controlled environmental conditions. Phytopathology 79:606-609. Two susceptible and four partially resistant tobacco genotypes were Mutant, NC-BMR 42, and NC-BMR 90 produced fewer and smaller evaluated for components of partial resistance to blue mold. Disease lesions, had lower sporulation capacity, and exhibited longer patent efficiency, incubation period, latent period, degree of colonization, and periods than susceptible genotypes. Breeding line NC-BMR 90 was sporulation capacity were measured under high and low inoculation superior to all other partially resistant genotypes in this study. The presence density in experiments conducted at the Southeastern Plant Environmental of multiple resistance components in NC-BMR 90 makes this line a Laboratory (North Carolina State University Phytotron), Raleigh, NC. desirable source of blue mold resistance. Results obtained in these Genotypes differed significantly for all components of resistance in all experiments corroborated field observations and indicate that deployment trials. Commercial cultivars Speight G-70 and McNair 944 were of tobacco germ plasm with partial resistance to blue mold should reduce consistently the most susceptible genotypes based on all components of onset and progress of blue mold epidemics. partial resistance measured. Partially resistant genotypes Chemical Additional keywords: Nicotiana tabacum, Peronospora tabacina. Tobacco blue mold, also known as downy mildew of tobacco derived from N. velutina) and Chemical Mutant (resistance (Nicotiana tabacum L.), is caused by the fungus Peronospora obtained after treating seeds of flue-cured tobacco cultivar tabacina Adam. Occurrence of blue mold is generally sporadic, but Virginia Gold with triethylene iminotriazine) (9); two resistant severe economic losses can occur when the disease reaches breeding lines, NC-BMR 42 (derived from the cross Ovens 62 X epidemic proportions. For example, an epidemic of blue mold in McNair 944) and NC-BMR 90 (derived from the cross Ovens 62 X 1979 resulted in an estimated $250 million loss to U.S. and KY 17) (12); and two susceptible commercial cultivars, Speight

Inheritance of resistance to black rot (Xanthomonas campestris pv. Campestris) in cauliflower (Brassica oleracea var. Botrytis)

Black rot disease caused by Xanthomonas campestris pv. campestris is a limiting factor in the commercial production of the cauliflower crop. Crosses were attempted between SN 445, a mid season cultivar resistant to black rot and two highly susceptible commercial cultivars (Pusa Snowball-1 and K-1). Studies of the F1's, F2's and back crosses indicated that SN 445, carries a dominant gene imparting resistance to black rot.

Glandular Trichomes of a Resistant Hybrid Potato Alter Feeding Behavior of the Potato Leafhopper (Homoptera: Cicadellidae)

Feeding and host acceptance behavior of the potato leafhopper, Empoasca fabae (Harris), on a hybrid potato bearing glandular trichomes was examined as was the expression of resistance to field populations of E. fabae . More than 75% of nymphs given access to the resistant hybrid failed to feed; all nymphs on a susceptible commercial cultivar initiated feeding. Average duration of time to first probe on the hybrid was 14.2 min, compared with 1.2 min on the susceptible cultivar. Acceptance and feeding success on the resistant clone were greatly improved following removal of glandular trichomes. In field plots subject to natural infestations of E. fabae, populations of adults and nymphs on the hybrid clone were reduced >80% compared with those on commercial potato cultivars.

Green Peach Aphid (Homoptera: Aphididae): Developmental and Reproductive Biology on a Solanum tuberosum × S. berthaultii Hybrid Potato

Development and reproduction of the green peach aphid, Myzus persicae (Sulzer), were compared on a resistant hybrid potato bearing glandular pubescence and a susceptible commercial cultivar. Removal of glandular trichomes from the Solanum tuberosum ssp. tuberosum (L.) × S. berthaultii Hawkes Fa hybrid improved aphid survival nearly 2-fold. compared with survival on foliage with intact trichomes. Longevity of adults and reproductive performance were significantly reduced on the resistant host compared with those on ‘Superior’. Excised foliage of the hybrid potato partially lost its defensive ability; loss in expression of resistance increased with the duration of time following excision. Except for reduction in adult weight, the adverse influence of resistance on maternal development and fecundity was not evident in daughters reared on the susceptible cultivar. Hybrid potato germplasm bearing glandular trichomes from S. berthaultii appears promising as a tactic for management of the green peach aphid.

Studies on glucosinolates in clubroot resistant selections and susceptible commercial cultivars of cabbages

Heads of 59 commercial cabbage cultivars, all susceptible to clubroot disease, and of 86 individual clubroot resistant cabbage plants of various breeding selections were analysed for their composition in glucosinolates, determined by quantifying their hydrolytic breakdown products, thiocyanate, goitrin, and volatile isothiocyanates. The mean thiocynate ion content was significantly lower in the breeding selections (120 μg/g dry weight) than in the commercial cultivars (204 μg/g). In contrast, the mean goitrin content was significantly higher in the breeding selections (193 μg/g) than in the commercial cultivars (35 μg/g). Similar to goitrin, the range of volatile isothiocyanates and total glucosinolate were higher in the breeding selections, but the mean contents of each were not statistically different between selections and cultivars. Fourteen cultivars and four selections were found to be free of goitrin; three cultivars, but no breeding selection were free of volatile isothiocyanates. The breeding selections will provide germplasm for breeding new clubroot resistant and low glucosinolate cultivars.

Inheritance of Seed Shape and Resistance to Ascochyta Blight in Pea (Pisum sativum L.)

SummaryTo ascertain the inheritance of seed shape and resistance to Ascochyta blight and to incorporate resistance in commercial cultivars, crosses were made between cv. Kinnauri, a round-seeded resistant source and commercially important cvs Bonneville, Lincoln, GC 141, and Selection 18, highly susceptible to disease but wrinkled-seeded. The F1, F2 and F3 data indicated that seed shape and resistance to Ascochyta blight is determined by two independently inherited genes. Round seed and disease resistance are dominant over wrinkled seed and susceptibility. Commercially desirable lines have been selected which combine the resistance gene of Kinnauri with wrinkled seed from susceptible commercial cultivars, and which also possess high pod yields and other desirable characters.

Inheritance of resistance to pea blight (Ascochyta pinodella) and induction of resistance in pea (Pisum sativum L.)

Pea blight caused by Assochyta pinodella does considerable damage to the pea crop every year. To ascertain the inheritance of resistance to pea blight and incorporate resistance in the commercial cultivars, crosses were made between Kinnauri resistant to pea blight and four highly susceptible commercial pea cultivars — Bonneville, Lincoln, GC 141 and Sel. 18. Studies of the F1's, F2's, back crosses and F3's indicated that Kinnauri carries a dominant gene imparting resistance to pea blight.

A Critical-Point Yield Loss Model for Cylindrocladium Black Rot of Peanut

Groundnut yield losses due to C. crotalariae were estimated for 2 commercial cultivars and 2 advanced-generation breeding lines which were evaluated in 10 field trials in 4 N. Carol. counties in 1980, 1981 and 1982. Results from trials in stratified fields and established plots, and from C. black rot simulations, were similar for a highly susceptible commercial cultivar (Florigiant), a moderately resistant one (NC 8C) and a highly resistant breeding line (NC 18229). A critical-point model for predicting incidence of C. black rot c. 1 wk before digging explained disease incidence-yield relationships when yield was expressed as the percentage of the max. yield at a location. Critical-point models for Florigiant, NC 8C and NC 1229 were obtained. In trials where epidemics developed naturally, mean incidence 1 wk before digging were 0.21-0.74, 0.17-0.53 and 0.13-0.33 and mean predicted yield loss 15-53%, 13-40% and 9-22% for Florigiant, NC 8C and NC 18229, respectively. A single critical-point model was not applicable over locations for NC 18016, which appeared to be less agronomically stable than the other lines evaluated in this study

Efficacy of Resistance to Root-knot Nematode in Snap Beans1

Abstract Four snap bean (Phaseolus vulgaris L.) breeding lines, resistant PI 165426, and 2 susceptible commercial cultivars were tested for resistance to root galling and root-knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood) reproduction under greenhouse and field conditions. Root gall indices, reproduction indices, and numbers of eggs/g of root were significantly less on resistant lines than on ‘White Seeded Provider’ in 2 greenhouse tests. In field tests, soil treatment with the nematicide DBCP resulted in significant control. In nontreated plots, resistant bean lines had less root galls than ‘Early Gallatin’. Plots planted with resistant lines had fewer M. incognita larvae than those with ‘Early Gallatin’. Mean yield of pods from resistant lines in nontreated soil was about 3 times the yield of ‘Early Gallatin’. Yield of pods from treated and nontreated subplots were not significantly different. These results indicate that resistance is equivalent to soil fumigation for root-knot nematode control in snap beans.

Inheritance of resistance to angular leaf spot (Isariopsis griseola Sacc.) in french bean (Phaseolus vulgaris L.)

Angular leaf spot (Isariopsis griseolaSacc.) is a serious disease of French bean in the hills of India and 40 to 70 per cent of the green pods are damaged and rendered unmarketable. Crosses were made between PLB 257, (Phaseolus coccineus L.), a red flowering pole tope, resistant to angular leaf spot, and Contender (Phaseolus vulgaris L.), a highly susceptible commercial cultivar. Studies of the F1, F2, and F3 progenies indicated that PLB 257, carries a recessive gene imparting resistance to angular leaf spot.

Inheritance of resistance to fruit rot (Phytophthora parasiticaDast.) in tomato (Lycopersicon esculentum Mill.)

Fruit rot disease caused by Phytophthora parasiticaDast. is a limiting factor in tomato production in Himachal Pradesh. 30 to 60 per cent fruits are damaged by this disease. Crosses were made between EC 54725 (Lycopersicon pimpinellifolium), a small tyuited type, resistant to fruit rot and four highly susceptible tomato commercial cultivars (Gola, Sioux, S12, and Lalmani). Studies of F1's, F2's and back crosses indicated that EC 54725 carries a dominant gene imparting resistance to fruit rot.

Evidence of Inheritance of Resistance to the Mexican Bean Beetle in Soybeans1

The inheritance of resistance to the Mexican bean beetle, (Epilachna varivestis Mulsant), in soybeans, (Glycine max L. Merr.), was evaluated using F3 populations. Four populations were obtained by crossing resistant plant introductions to susceptible commercial cultivars. Ratings of percent foliar damage were made on F3 progeny rows containing 25 plants. Progeny rows were replicated two to four times depending on seed availability. Parental lines were also grown for comparison. Population means were recorded and estimates of genotypic, environmental, and phenotypic variances computed. Broad sense heritability estimates were calculated for each population. Significant genetic variance occurred in all populations. The results suggest a quantitative inheritance of resistance in soybeans. Percent foliar damage approximated a normal distribution in the F3 populations exposed to a moderate to heavy MBB infestation. Population means of the F3 progeny were not significantly different from their mid‐parent values, alluding to a primarily additive gene action. Several F3 progeny rows with levels of resistance equal to the mean of the resistant parent were observed. Involvement of only two or three major genes is suggested from our observations, although the exact number of genes controlling resistance could not be determined. Broad sense heritabilities ranged from 44% to 81% under the conditions of this investigation.