Craigs Royal Research Articles

Host–pathogen interaction between Phytophthora infestans and Solanum tuberosum following exposure to short and long daylight hours

The influence of short and long day length on the expression of qualitative and quantitative resistance to Phytophthora infestans in potato was studied. The incompatible interaction was tested for available set of isolates avirulent in greenhouse conditions to potato Black’s differentials possessing the genes: R2, R5, R6, R8, R9, R10, and standard potato cultivar Tarpan (no known R gene). The avirulent isolates either were completely avirulent regardless of plant growing conditions, or they infected leaflets of these differentials more frequently when plants were exposed previously to short day conditions than to long day conditions. This study highlights the importance of day length, among many other factors which are controlled, in testing the expression of the virulence of P. infestans isolates. In compatible interactions, when quantitative resistance was evaluated in differentials with gene R1, R3, R4, R7, R11, and potato cultivar Craigs Royal (no known R gene), stronger infection expressed by lesion growth rate, as well as stronger sporulation, were observed on potato leaflets of plants exposed to short day for 6–7 weeks before inoculation. The analysis of variance revealed a significant contribution to variation in lesion growth rate of day length, genotype, as well as day length by genotype interaction. Significant influence of isolate, and genotype, but not day length, on the expression of the incubation period was found. The results indicate the necessity of evaluating components of partial resistance present in potato lines used in breeding potato resistant to P. infestans in destined day length growing conditions.

An approach to determining optimum tuber planting densities in early potato varieties

SUMMARYThirteen experiments conducted near Tenby, Dyfed, between 1973 and 1980, examined the effects of seed-tuber weight and within-row spacing on tuber yields of seven potato varieties grown for early production. These data have been used in an attempt to develop an approach to the determination of optimum tuber planting densities in early crops which will provide agronomists with logically applicable principles. Tuber planting densities, which maximized the net crop return (ware value minus seed cost), were estimated for eight ratios of seed cost to ware value ranging from 0·25 to 8·0. Optimum tuber planting densities decreased with the use of higher ratios of seed cost: ware value and heavier seed, except for ratios of 0·25 and 0·50 applied to yields of tubers > 25 mm harvested in June. In general, later harvesting together with the use of larger riddle sizes give a lower optimum density with ratios < 2·2·0. Optimum densities for Red Craigs Royal, Ulster Sceptre and Vanessa were higher than for the other varieties.The results provide an illustration of how to approach the problem of selecting tuber planting densities in order to maximize net crop returns in early potato varieties.

Effects of physiological age of seed tubers on seed yield and regrowth of progeny tubers in potatoes

SummaryFour experiments are reported in which the effects of a range of physiological ages of seed tubers on growth and yield in seed crops and regrowth of the progeny seed were studied. Increasing the age of seed in Home Guard, Arran Comet, Pentland Javelin and Désirée advanced emergence, tuber initiation and early growth but restricted leaf area index and reduced the number of tubers and seed tuber yield. In these varieties increasing the physiological age of seed shortened the dormancy of the progeny seed and slightly increased sprout lengths at replanting but in Home Guard had no effects on field growth and tuber yield.In a further series of experiments at Tenby seed of five varieties (Home Guard, Red Craigs Royal, Désirée, Maris Piper and Stormont Enterprise) was multiplied over 2 years using husbandry methods designed to produce seed of contrasting ages. Once-grown seed from Tenby which had been planted and harvested early in the season was stored at either 4 or 12 °C and grown again at Tenby before being stored again at either 4 or 12 °C. The seed resulting from this multiplication over 2 years was compared with seed imported from seed-growing areas stored at the two temperatures. The seasons for the two multiplications at Tenby (1975 and 1976) were hot and were followed by an especially cold and late spring yet few differences between seed from Tenby and other areas could be detected. Where seed from different areas entered sprouting temperatures at different times and therefore produced different ages of seed at replanting large effects on yield were found. Storage temperature had large effects on regrowth of tubers in Home Guard, Red Craigs Royal and Stormont Enterprise for storage at 12 °C produced ‘little potato disorder’ in the majority of plants in one storage phase while storage at lower temperature produced full plant stands and yields. The results provided no support for the suggestion that repeated multiplication in warm lowland areas may lead to cumulative deterioration in the performance of seed.

Effects of site of seed production on seed yields and regrowth of progeny tubers in potatoes

SUMMARYNine experiments are reported in which effects of site of seed production on dormancy, sprout and field growth of progeny tubers were recorded. The experiments used early varieties, Home Guard (four experiments), Red Craigs Royal (three experiments) and Arran Comet (two experiments) and in each, seed crops were grown with similar husbandry at sites differing in altitude and location in western England and Wales. There was no consistent effect of site of seed production on the timing of the end of dormancy, and the maximum effect in any year was 11 ± 1·2 (S.E.) days. The small effects of site on dormancy influenced initial sprout lengths, and this effect usually persisted up to planting in Home Guard and Red Craigs Royal, although the effects were small in magnitude. There was no effect of site of seed production on sprout lengths at planting or on field growth and yields in Arran Comet. In the other two varieties there was no effect of site of seed production on yield at early harvests, but at later harvests seed from cooler upland sites sometimes significantly outyielded lowland seed. There was, therefore, no evidence to support the view that locally produced seed was advantageous for early potato production. The results, together with those of the concurrent series with maincrop varieties reported by Wurr (1979), show that on half the occasions on which yields were measured covering the whole of the harvesting period, site of seed production had no effect on yields. In these experiments with early varieties effects of site occurred only at harvests later than the commercial harvesting of such old seed. It is therefore suggested that site of seed production is a much less important determinant of tuber yield than hitherto suggested, and of little practical significance.

Wound healing in potato tuber tissue. 1. Effects of maturity at harvest

Potatoes of cvs Record (maincrop) and Red Craigs Royal (second early) were harvested at intervals from 22 August to 14 October. Half of the plots were mechanically defoliated on 22 August, by which date haulms of cv. Red Craigs Royal were largely dead. Tubers of cv. Record were immature at the first lifting date and matured thereafter, particularly after defoliation. Wound healing rates were assessed from the ability of discs of tuber tissue, cut the day after harvest, to become resistant to the loss of water vapour as suberization progressed at high relative humidity. Cv. Red Craigs Royal showed little variation in wound healing rate. Wound healing in cv. Record became more rapid with increasing maturity, particularly after defoliation when it reached a maximum by 1 October. After storage until March in the following year, the effect of maturity at lifting on wound healing rate was no longer evident.

Effects of date of planting on plant emergence, leaf growth, and yield in contrasting potato varieties

SUMMARYFive experiments which studied the effects of a wide range of dates of planting on contrasting potato varieties in Pembrokeshire are reported. In three experiments (1976–7) four early varieties (Home Guard, Arran Comet, Irish Peace and Ulster Sceptre) were sprouted from the end of dormancy and compared at four dates of planting, which began as soon as soil conditions allowed (February in 1975 and 1976 and March in 1977). In these experiments all early-emerging treatments were damaged by frost and in 1975 and 1976 date of planting had little effect on leaf area index or yield. In 1977 planting in late April delayed and increased peak leaf area index but reduced yields throughout harvesting. In all experiments the emergence of varieties was affected by date of planting. The varieties with the longest sprouts emerged first only from the earliest plantings; at late plantings all varieties emerged together, which suggests that rate of post-planting sprout elongation decreased in this old seed as planting was delayed despite increasing soil temperatures. The implications for testing of early varieties are discussed.In two further experiments two early varieties (Home Guard in both years and Red Craigs Royal and Arran Comet in 1 year) were compared with three maincrop varieties (Désirée, Maris Piper, Stormont Enterprise) using seed which did not begin to sprout until January at dates of planting beginning in March. Sprout length was again poorly related to earliness of emergence. Delaying planting delayed and increased peak leaf area index in all varieties but only increased yields in the early varieties which had the smallest leaf areas. In maincrop varieties date of planting had little effect on final yields. In these years there were long periods without rain and in 1976 yields were limited by the amount of water available from the soil, for as each treatment exhausted this supply bulking ceased.

Growth and Yield in Pure and Mixed Crops of Potato Cultivars

SUMMARYExperiments were made between 1977 and 1979 to investigate the possibility of raising potato yields by mixing together cultivars having different growth patterns. The experiments also included mixtures of unsprouted and sprouted seed of the same or different cultivars. In the first experiment (1977) Pentland Crown was mixed with Arran Pilot, Red Craig's Royal or Désirée and the binary mixtures (1:1) compared with the pure stands of each. Yield of tubers from the mixtures did not differ significantly from the mean of two components planted alone at wide or narrow spacing of the seed tubers. Two experiments with identical treatments (1978) included mixtures of Majestic and Désirée and of each cultivar with unsprouted and sprouted seed. Mixtures (1:1) yielded more tubers than the mean of the two components planted alone and at final harvest in one experiment unsprouted and sprouted Majesties gave 7·6 t/ha more than the mean of these and 6·9 t/ha more than the more productive culture (P < 0·05). Similar differences were obtained in the second experiment.In the final experiment (1979) the degree of sprout development at planting time was varied in the cultivar Majestic. Short or long sprouted seed was mixed with unsprouted seed and long sprouted Désirée was also mixed with unsprouted Majestic. Mixtures of the unsprouted cultivar with either long sprouted Majestic or Désiré exceeded, significantly, the mean yield of components planted alone by 4·1 and 5·8 t/ha, respectively, at a high level of fertilizer. As a mean of three experiments the mixture of sprouted and unsprouted Majesties yielded 6·26 t/ha more tubers than the mean of the components and 4·27 t/ha more than the higher yielding component in pure culture. Better light interception due to higher leaf area duration and a more persistent leaf canopy appeared to produce these effects.

Effects of date of planting on growth and yield of contrasting potato varieties in Pembrokeshire

SummaryFour experiments over 2 years which examined the effects of date of planting (from mid-March to early May) on the growth and yield of early, second early and maincrop potato varieties are described. In two experiments the seed used was physiologically old (heavily sprouted) and in the other two experiments relatively young seed (limited sprout development) was used. In the early variety, Home Guard, tuber yield at maturity was unaffected by delay in planting when physiologically old seed was used but increased leaf area and higher tuber yields resulted from later planting of younger seed. With both types of seed the maincrop varieties, Desirée and Maria Piper, produced larger leaf areas from later planting in one year but smaller leaf areas in the other year. In both years with both types of seed, tuber yields at the end of August were higher from the earlier plantings of these varieties. The physiologically young seed of Red Craig's Royal behaved in a similar manner to the maincrop varieties and the physiologically old seed behaved in a similar way to Home Guard.Any yield advantages of early varieties over maincrop varieties from any date of planting were small and short-lived and the physiological reasons for differences between varieties are discussed in the light of these results. It is suggested that the current classification of varieties is unjustified and that variety testing should take more account of the effects of physiological age.Tuber yields from the maincrop varieties were very high (60·80 t/ha) and this is attributed to the synchrony of leaf growth and increasing light receipts which may be readily achieved in the mild springs of W. Wales.

Field and glasshouse experiments on the control of potato mop‐top virus

SUMMARYField observations during 3 yr on a stock of potato cv. Red Craigs Royal partially infected with potato mop‐top virus (PMTV) confirmed that the virus was passed by an infected mother plant to only a proportion of its progeny tubers, and showed that in this cultivar symptomless plants gave rise only to symptomless progeny. The elimination of PMTV from stocks can therefore be greatly accelerated by removing symptom‐bearing plants. Infected potato tubers were not freed from PMTV by treating them at 37 °C for up to 8 wk. Treating ‘seed’ tubers bearing powdery scabs that contain PMTV‐carrying resting spores of Spongospora subterranea with formaldehyde or organo‐mercurial fungicide greatly decreased PMTV establishment when the tubers were planted in previously uninfective soil, but fumigation with 2‐aminobutane was ineffective.Decreasing the pH of infective soil to 5‐0 by applying sulphur greatly decreased the infection of potato cv. Arran Pilot with PMTV and S. subterranea in field experiments, but this treatment did not eliminate either; when the pH of treated soil was raised the transmission of PMTV resumed. Treating infective soil with a range of fungicides greatly decreased the infection of Nicotiana debneyi bait seedlings in glasshouse experiments but only calomel at 75 kg/ha controlled spread of PMTV and 5. subterranea to potato in field experiments. In other field experiments, applying zinc frit, zinc sulphate or zinc oxide to infective soil greatly decreased the spread of both to potato. The amount of zinc required increased with increase in clay content of the soil. However, treatment with zinc compounds did not eliminate PMTV‐carrying vectors from soil, and when treated soil was diluted with autoclaved soil many of the bait seedlings planted in the mixture became infected. The zinc frit was phytotoxic because of its boron content but zinc sulphate and zinc oxide caused little or no decrease in tuber yield. The zinc content of potato tubers was increased but not doubled in zinc‐treated plots, and during the first year after treatment the zinc content of topsoil decreased greatly. The zinc content of ryegrass grown after potatoes was greater than of potato tubers but did not reach a level considered dangerous to livestock. Treatment of soil with sulphur, zinc oxide or calomel may be useful for small plots used in the early stages of propagation of virus‐tested potato clones where there is risk of infection with PMTV.

Growth of Erwinia carotovora var. atroseptica and E. carotovova var. carotovora in Potato Stems

SUMMARYThe growth of Erwinia carotovora var. atroseptica and E. carotovora var. carotovora in stems of potato cultivars Majestic and Red Craigs Royal is reported. At high daily maximum temperatures, all isolates grew logarithmically for varying periods. Thereafter E. carotovora var. atroseptica populations generally increased and incited blackleg, while E. carotovora var. carotovora remained stationary or fell and either failed to incite blackleg or brought about a fast soft rotting (hollowing‐out) of the stems. Growth of either variety, especially of E. carotovora var. carotovora was retarded at lower daily maximum temperatures. There was a reduced growth in Red Craigs Royal compared with Majestic.For the blackleg symptom to appear in Majestic, a threshold population of c. 108 bactcria/g of stem was considered a pre‐requisite.

DEVELOPMENT OF CHLOROPLASTS FROM AMYLOPLASTS IN POTATO TUBER DISCS

SUMMARYWhite potato tuber tissues (Solarium tuberosum, vars. King Edward and Craigs Royal), contained carotenoids but did not contain either protochlorophyll or chlorophyll. On illumination of tuber discs, the accumulation of chlorophyll a and chlorophyll b began simultaneously after 19 hours and continued for 3 weeks. This greening process was associated with a synthesis of galactolipids.Light of intensity 750 1× was sufficient to induce maximum greening and to cause greening throughout the disc. Blue light was more effective than orange or green light.Chlorophyll accumulation in tuber discs was inhibited by cycloheximide, chloramphenicol, lincomycin, δ‐aminolaevulinic acid, benzyladenine, and high concentrations of sodium arsenate and potassium cyanide. It was unaffected by 2,4‐D, laevulinic acid and malonic acid. When green discs were returned to darkness, the total chlorophyll content remained constant over a period of 7 days but the ratio of chlorophyll a to chlorophyll b decreased.These results are discussed in terms of the control mechanisms and differentiation processes involved in the development of chloroplasts from amyloplasts.

Ecological studies on potato mop‐top virus in Scotland

SUMMARYPlants with symptoms of potato mop‐top virus (PMTV) occurred in many commercial seed stocks of Arran Pilot and Red Craig's Royal potato in Scotland, but their incidence rarely exceeded 5%. In nuclear stocks of seed potatoes, most varieties examined in 1967 and 1968 were infected at one or more locality, but infected plants did not occur in all clones or at all stages of propagation of any one variety. infection of nuclear stocks resulted both from propagation on virus‐infested land and from unwitting selection of infected plants to start new clones. PMTV was detected in farm soils ranging from light sands to heavy loams, in five Scottish counties. Soil was infested throughout the ploughed layer but the severity of infestation varied greatly within any one field; some sites of former potato clamps were heavily infested. PMTV was detected in field soil 12 years after potatoes were grown.In glasshouse tests many British crop and wild plants were colonized by Spongospora subterranea. Within some families all species tested were moderate to good hosts. (Solanaceae, Chenopodiaceae and Cruciferae), in others, species differed greatly in susceptibility (Compositae and Umbelliferae), and in a few, species were poor hosts or were not infected (Caryophyllaceae and Gramineae). Of the British crop and weed species that were moderate to good zoosporangial hosts of S. subterranea, only Solanum nigrum, potato, spinach and sugar beet were hosts of vector‐borne PMTV. Potato probably survives between potato crops mainly in the resting spores of S. subterranea. PMTV was probably first brought to Europe with potatoes from South or Central America.

The stability of L1-mutant periclinal potato chimeras

The varietiesRed Craigs Royal andRed King are periclinal chimeras with the constitution, L1 uniform red-L2 white-splashed-pink-L3 white-splashed-pink. About 1 in a 100 plants has a tuber or part of a tuber showing reversion to L1 white-splashed-pink.

The effect of CCC, nitrogen and potassium on the growth and yield of two varieties of potatoes

SUMMARYThe two experiments described here were the 3rd and 4th in a series of experiments investigating the effect of time of application of nitrogen and potassium on the growth and yield of potatoes.The effect of applying all the fertilizer nitrogen in the seed bed was compared with applying all the nitrogen at the time of tuber initiation or dividing the dressing between these times. Similar times of application were tested for potassium. CCC was applied after a leaf area index of 3 had been reached (on all but the no N treatments) in order to offset the tendency for late nitrogen to increase stem growth, but to avoid any tendency for CCC to depress yield by reducing leaf area indices (L) below an assumed optimum value of 3. These treatments were applied in separate experiments to a second early variety (Craig's Royal) and a maincrop variety (Pentland Dell), planted a month later.In both crops the response to nitrogen was large and delaying or splitting the application of nitrogen increased tuber yield compared with nitrogen applied in the seed bed. Responses to potassium were small, but there was a tendency for split applications to be superior to late or early applications.The beneficial effect of delayed or split applications of nitrogen was associated with an improvement in the recovery of nitrogen in the crop which was largely ascribed to a reduction in loss due to leaching. Total and tuber dry-matter yields were linearly related to leaf area duration (D) in both crops, although the earlier variety was more efficient per unit of D. High values of L (6) were recorded for both crops, but there was no indication of an optimal value of L; consequently CCC which reduced L also reduced yield. D was closely related to the maximum quantity of nitrogen accumulated in the leaves per unit area of ground.

The effect of CCC and nitrogen on the growth and yield of the second early potato variety Craig's Royal

SUMMARYThe experiment described here is the second of a series of experiments investigating the effect of the time of application of certain plant nutrients on the growth of the potato crop. In this experiment all combinations of three rates of nitrogen (0, 0·75 and 1·50 cwts nitrogen per acre), two times of application (at planting and at the time of tuber initiation) and two rates of application of CCC (0 and 4 lb/acre applied twice, shortly after emergence) were tested and studied by the technique of growth analysis.There was a linear relationship between leaf area duration (D)and tuber dry matter yield, D accounting for 95 % of the variation in the latter. The maximum amount of nitrogen accumulated in the leaves (Nmax) was linearly related to D, and accounted for 86 % of the variation in D. This relationship was improved if separate regressions were calculated according to whether CCC had been applied or not. Calculated in this way, the regressions indicated that more nitrogen was required for a given value of D when plants were treated with CCC.Delaying the application of nitrogen resulted in a considerable improvement in the recovery of fertilizer nitrogen (ammonium nitrate). A heavy dressing of nitrogen at the time of planting did not enable the crop to take up sufficient nitrogen for maximum yield. Because of these factors, delaying the application of nitrogen significantly increased tuber yield at both rates of nitrogen tested.Increasing the rate of nitrogen and delaying its application tended to increase the proportion of stem in the total dry matter; CCC had the opposite tendency. CCC, however, reduced leaf area and the mean effect of CCC was to reduce tuber yields. While there wore no significant interactions between CCC and nitrogen treatments on final tuber yield, it was observed that CCC slightly increased yield when the highest rate of nitrogen was applied late. Ways are suggested in which CCC may be more effectively used.

The effect of the time of application of nitrogen and potassium on the growth of the second early potato, variety Craig's Royal

SUMMARYThe effect of time of application of nitrogen and potassium on the growth, development and yield of the second early variety Craig's Royal was studied by the technique of growth analysis. There was an indication that witholding nutrients led to the earlier initiation of tubers, but this was of no practical consequence and all treatments affected tuber bulking rate rather than the duration of bulking. Compared with early application, late application of nitrogen depressed tuber yield, although total drymatter yield was not affected. Late application of potassium, however, increased tuber yield; this was associated with an improvement in the recovery of applied potassium. Delaying the application of nitrogen also resulted in its more efficient recovery in the crop. Late application of potassium improved the recovery of early applied nitrogen and vice versa. Reasons are put forward to account for these effects.

Studies in potato agronomy. II. The effects of variety and time of planting on growth, development and yield

1. A factori al experiment involving four varieties (Ulster Chieftain, Arran Pilot, Craig's Royal and Ulster Torch) and three times of planting (28 March, 13 April and 2 May) was undertaken with a view to investigating the effects on growth development and yield of these factors. Only a limited amount of data was obtained in respect of Craig's Royal, because of its extreme variability in the first two times of planting. In addition, data in respect of King Edward and Majestic planted on the second date in an adjacent experiment are discussed.2. In general, yields from Ulster Torch were about twice as great as those from Ulster Chieftain, with the other varieties occupying intermediate positions. The total yield of Ulster Chieftain increased with delay in planting, while in Arran Pilot, Craig's Royal and Ulster Torch, yield was greatest at the intermediate planting date, slightly lower than this at the first, and lowest at the third. Ware yield as a proportion of the total increased with delay in planting.