Search Results
Concern over insecticide usage for control of European corn borer (Ostrinia nubilalis Hübner) in sweet corn (Zea mays L.) in recent years has increased the need for genetic control. Our objectives were to determine the degree of ear feeding resistance transmitted by resistant breeding lines to testcrosses and to investigate the relationship between resistance and both ear silk channel length, and infestation level. Testcrosses averaged 35% acceptable ears compared to 7%. for two commercial control hybrids and 45% for the lines per se when artificially infested at the ear tip at mid-silk at two locations. Generally, resistance in the testcrosses was closer to the resistance level of the resistant parent, indicating good combining ability for resistance. Heterosis above the resistant parent was found in 8 of 12 testcrosses. Across entries, ears having relatively longer silk channel length tended to have less damage but the relationship was not strong (r 2 = 0.24, P < 0.01). When silk channels were artificially shortened at infestation, resistance levels were lower, but five of seven lines had a higher proportion of acceptable ears than did the control hybrid. Across increasing levels of infestation from 50 to 200 neonate larvae per ear eight of nine lines had higher resistance (P < 0.05) than the control.
Attention has been given in recent literature to crop breeding for heat tolerance, but, as with certain other physiological traits, such as photosynthetic efficiency, practical gain has lagged. The question remains as to whether heat tolerance can be improved, and, if so, if it can most efficiently be improved by a holistic approach, as in breeding for yield following timely high temperature levels in the field environment, or whether the breeding for heat (and drought) tolerance components in the laboratory would be feasible. At issue is the identification and repeatability of key plant responses, such as cell membrane damage, heat shock protein formation, increased ethylene output and other responses, and the relevance, effectiveness and cost of screening for such traits. Results from our laboratory, and the work of others, will be reviewed.
Attention has been given in recent literature to crop breeding for heat tolerance, but, as with certain other physiological traits, such as photosynthetic efficiency, practical gain has lagged. The question remains as to whether heat tolerance can be improved, and, if so, if it can most efficiently be improved by a holistic approach, as in breeding for yield following timely high temperature levels in the field environment, or whether the breeding for heat (and drought) tolerance components in the laboratory would be feasible. At issue is the identification and repeatability of key plant responses, such as cell membrane damage, heat shock protein formation, increased ethylene output and other responses, and the relevance, effectiveness and cost of screening for such traits. Results from our laboratory, and the work of others, will be reviewed.
Abstract
AS9 is a sugary-1 breeding population of sweet com (Zea mays L.) having moderate to high resistance to first brood attack (leaf feeding phase) by the European corn borer (Ostrinianubilalis, Hübner). The first sugary-1 source material having such resistance, it has been composited from diverse sources and is being released for its potential value in sweet corn breeding.
Abstract
Fruit of ‘Ruby Red’ grapefruit (Citrus paradisi Macf.) were treated postharvest with sodium-o-phenylphenate (SOPP), benomyl, imazalil, and etaconazole and stored under ambient conditions or were treated with SOPP, imazalil, and etaconazole and stored at 12°C. Imazalil and etaconazole were as effective as benomyl under ambient conditions and were more effective than SOPP under refrigerated conditions; 85% of the stem-end-rot was caused by Phomopsis citri (Fawc).
Abstract
Procedures for forced field infestation of maize with European corn borer egg masses, placed to simulate possible natural ovipositional sites and to emphasize damage to the ear, were compared. A growth chamber procedure using excised ears and a free-choice (preference) infestation procedure were also used. Forced infestation in the field permitted infestation at a uniform relative maturity and uniform development of borers from time of infestation to evaluation. An ear-and-leaf infestation procedure appeared to be the most appropriate for simultaneous evaluation of kernel damage and stalk tunneling. Estimated heritabilities, using this procedure on 2 segregating populations, were 0.71 and 0.84 for kernel damage and 0.39 and 0.79 for stalk tunneling. Phenotypic correlations among 3 ear damage criteria were noted (r = 0.42 to 0.46). Evaluation based on kernel damage alone, excluding cob tunneling and number of surviving larvae, was considered sufficient. There was no evidence that kernel damage was influenced by level of stalk tunneling.
Abstract
Artificial was compared to natural infestation for evaluating kernel damage and stalk tunneling on maize (Zea mays, L.) caused by European corn borer (Ostrinia nubilalis, Hiibner) larvae. Under conditions of natural infestation, differential damage levels among families were more closely correlated with silk date than oviposition frequencies on the host plants. The association between damage and silk date was reduced following artificial infestation. Artificial infestation, which permits infestation at a common stage of maturity (full silk), a uniform and greater insect population on host plants, and a uniform opportunity for larval development on the ear from time of infestation to time of evaluation, is preferred for differentiating maize genotypes for borer resistance.
Abstract
The inheritance of interlocular cavitation (IC), characterized by rupture of the soft, parenchymatous endocarp tissue between the seed locules in developing snap bean pods, was studied using 6 parental cultivars, all 30 possible F1 progenies grown in the greenhouse, and the 30 F2 families grown at various planting dates at 2 field locations.
IC appeared to be a highly heritable character conditioned by a predominantly additive polygenic system with partial dominance for resistance. Reciprocal effects were negligible. Neither epistasis nor transgressive segregation was detected. Order of susceptibility among genotypes was maintained over the wide range of environments. Genotype × environment interaction was significant, but was relatively small compared to total genetic variability. Association between greenhouse-grown F1 and field-grown F2 plants was high for degree of IC, suggesting that F1 performance might be informative in choosing superior crosses. Breeding progress appears to be feasible in a program designed to utilize the large amount of additive genetic variance.
Abstract
The influence of leaching and water quality on the service life of Cu-treated burlap was investigated. Copper ammonium carbonate (CAC) and copper naphthenate (Cu Nap) treated burlap were more resistant to leaching with distilled H2O than CuSO4-treated burlap. When evaluating water quality, burlap treated with CuSO4 was found to be susceptible to ionic exchange of the Cu by Fe, Ca, Mg, Na or K. Soil burial tests of burlap treated with Cl or SO4 salts of Cu, Fe, Ca, Mg, Na and K resulted in the replacement of Cu and burlap deterioated within 1 month which was similar to untreated burlap. Water quality of leachates from 12 organic holding media such as pine bark, contained Ca and Mg in concentrations high enough to replace Cu in CuSO4-treated burlap. An inert holding media such as river sand would be preferred to reduce ion replacement and thus extend the service life of Cu-treated burlap.
Abstract
Many individuals view the need to deliver an occasional paper at a national meeting as an occupational hazard of their profession. Others take the more optimistic view that the presentation of a paper not only presents an opportunity to assist others, but also offers an excellent means to accelerate one’s career and argue that as much attention should be given to the presentation (both oral and written) as was given to the actual research. There is more at stake than one’s own reputation; after all, in an oral presentation you are holding your colleagues captive.