Albino Wheat Plants in Eastern Oregon and Washington Fields - PDF document

Albino Wheat Plants in Eastern Oregon and Washington Fields Richard Smiley Oregon State University, Pendleton April 12, 2001 This information relates to the albinism phenomenon in winter wheat and barley seedlings as they start growing in the spring. The albino tissue is not observed during the autumn or winter. Several points can be made. The cause is unknown, the albinism is not new and does not appear to be increasing, albinism is occurring in both wheat and barley, the percentage of affected plants appears to be very low (typically a fraction of one percent), the plants expressing albinism really stand out, the striking appearance of albino plants make it very easy to over - estimate the percentage of affected plants, the phenomenon has been reported throughout the inland Pacific Northwest (WA, OR, & ID), the albino plants will die, the phenomenon is unlikely to affect yield, and albinism seemingly differ in response to certain varieties, field histories, planting date, and year - to - year seasonal variat ions. The occurrence of albinism does not appear to me to be increasing in occurrence. Concerns have arisen during early spring during the past 25 to 30 years, if not longer. Richard Smiley and other scientists investigated this phenomenon rather inten sively duri ng 1989. They failed to reach any conclusion but did seem to exclude some ideas that had been kicked around (herbicides, specific seed lots or varieties, Russian wheat aphid, viruses, etc.). Virologists and pathologists in OR, WA & MT couldn ’ t pin it down to any of the known viruses or other diseases. Arnold Appleby did not feel that it could be a response to a herbicide, and it was clear that there was no commonality among treatments where albinism was observed. Glenn Fisher was quick to discou rage us from thinking it might be an interaction of Russian wheat aphid toxin and the environment -- there wasn ’ t any evidence of aphid feeding on symptomatic plants, and it occurred in crops planted after the majority of aphid flights had ceased. They did n’t pursue it further because the incidence of plants was always very low and the albino plants died so early that the adjacent plants must surely have kept on an extra tiller or two to take advantage of any additional light, moisture or nutrients. From a crop production perspective it seemed that a study of this phenomenon would cost much more money than it deserved. Studies would have required controlled temperature rooms capable of freezing temperatures, or elaborate planting designs under field conditio ns. Each would be expensive, and the field studies would have really been a risky situation because the occurrence of albinism seems to vary from year to year. The extension diagnostic pathologist at WSU - Prosser (Ellen Bentley) served as the focal point for a re - run of those discussions during 1998. Don Wysocki coordinated a similar exchange of observations and opinions during 1999. The albinism appears to occur more frequently in certain varieties but, to our knowledge, that observation has never been documented or examined in research. Some varieties mentioned during emails over the past 20 years have included Stephens, Daws, Hyslop, MacVicar, and Rod. But that list is certainly not conclusive or inclusive. Many of the commercial field men report mor e of this problem occurring in rotations of winter wheat and spring peas. But it has also been seen in winter wheat/summer fallow rotations. We suspect that it appears more in summer fallow is because that rotation system is almost always planted early (Se ptember) while stored moisture is available to establish the stand. In contrast, the pea rotations are almost always planted late because there is no shallow stored moisture and the seed is planted shortly before or after the first substantial rain, usuall y in mid - October or later. Emergence and stand establishment on the pea rotation ground is therefore much later than in most summer fallow rotations. That would jive with the date of planting information that Richard Smiley observed in Stephens wheat plant ed in a single field at Pendleton this year. Albino plant populations were as follows: none for the Sept 22, 2000 planting, 0.05% for the Oct 5 planting, and 1.47% for the Oct 22 planting. The premise that this phenomenon is related to an aberrant gene in the wheat pool has been kicked around for at least three decades. To our knowledge, the concept was first suggested by Clarence  Pete  Peterson, USDA - ARS and subsequently WSU wheat breeder. Pete felt that is was a genetic link and had some unknown common parent way back in the early days of the breeding program. Roland Shirman, WSU extension agent in Columbia County, WA (Dayton) st ated in 1999 that he thinks it might be related to emergence date and winter severity. In our situation, it would appear that we concur that late plantings, for whatever reason, cause the symptoms to be worse. Last autumn our region started getting recurr ent rains on September 3, which is unusually early for this area. The soil was moist nearly continuously for a month or so. That allowed winter annual weeds and volunteer cereals to germinate and emerge, and allowed growers to kill those plants off before planting the winter wheat. But it also led to some delayed plantings that were ultimately put into rather cool soil. Then we had air temperatures of 20oF or lower during at least one day every month during November, December, January and February. The soil temperatures at seed depth were often hovering around the freezing mark during the winter. So we had the possibility of emergence in cool to cold soil, and episodes of fluctuating temperatures during an open winter (very little snow). In 1998, in respons e to the WSU - Prosser inquiries, Ron Rickman (USDA - ARS wheat growth modeler at Pendleton) responded that  The white plants are effectively a thinning process - probably not a desirable one and definitely not a planned one.  Betty Klepper (USDA - ARS wheat phy siologist, now retired) felt that the albinism was caused by a lethal gene in some wheat varieties. She thought it might be triggered by some unknown but precise set of environmental conditions. Neither Rickman nor Klepper felt that albinism affected yield . The internet is a great tool for obtaining more information. A search of the literature indicates that albinism is a common genetic defect associated with tissue culture work with many genera of monocots, including rice, corn, wheat, barley, and some grasses. In certain cereal genera the phenomenon is also well documented in field and growth chamber studies. Unfortunately, we are not currently aware of comparable research with wheat. The following reports are shared because they seem pertinent. We c an provide the web access addresses for each of these reports if that should be necessary to document the content of these summaries. In a 1998 report from the Chinese Academy of Sciences - Institute of Botany (in Beijing), botanists reported on alteratio ns of whole leaf protein by a temperature - sensitive chlorophyll deficient rice mutant. Temperature variations could turn on and off the expression of a chlorophyll synthesis protein. The regulatory mechanism wasn ’ t understood but they could create albinism with certain fluctuations in temperature. In our case, we see some plants with perfectly normal (green) lower leaves and an albinized younger growth. Earlier this week we observed some green leaves with albino sectors between green leaf ends and leaf shea ths. Could this temperature sensitive effect on protein synthesis be occurring in our wheat? We also learn from the internet that barley has at least three well - documented and formally named albino mutant genes that, when triggered, create albino seedling s. They are all recessive genes and create albino plants that die at the two - to three - leaf stage. One such mutant, abo11, allows normal green plant growth under regular temperatures but creates albinism in subsequent growth after the plant is subjected to temperatures below 44oF. The effect is restricted to young seedlings -- as plants age they no longer respond to low temperature with the albinism effect. The study of these genes followed the first description of a low - temperature form of albinism in bar ley. The initial observation was published in 1922 and the genetic studies have been more recent. This report was in a USDA research summary of mutant gene forms for wheat, although it was not specifically stated that these genes also occur in wheat. A we b page for a genetics course at Colorado State University states that  many mutations are known to confer temperature sensitivity on phenotypic expression.  However, it appears that the most common expression of this system is that a gene product is functi onal at a lower temperature and loses function at a higher temperature, generally reflecting the loss of heat stability of a functional protein (usually an enzyme) due to an amino acid substitution. They don ’ t exclude the reverse temperature relationship, which would better fit our observations on albinism. A study of barley mutants by geneticists at the University of Helsinki and the Plant Breeding Section of the Agriculture Research Council (in Finland) showed that albino mutants varied in expression fro m year to year. In some  relatively warm  years the mutants could survive the full season in Finland. During other seasons none of the mutants were able to survive the winter. The authors of that report concluded that  the response of the all - mutant plants was assumed mainly to be caused by the growing temperature.  They then performed controlled temperature studies and could induce the albinism at 40oF, and the plants survived for several months before all died. At 61oC the mutants had white, white and gre en stripes, and whitish and green tissue sectors, and all were stunted but survived. At 68oF all plants with the mutant genes looked and grew normally. They concluded that  This experiment confirmed the field observations, indicating, that the mutant is te mperature - sensitive (Figure 1). The pictures of their mutant barley plants in the controlled - temperature study look very similar to what we are observing on wheat plants in the field. Their genetics studies showed that the pigment deficiency is inherited w ith the cytoplasm, and they referred to some work at WSU (Pullman) in which the barley geneticists reported that five cytoplasmic mutants in barley were temperature sensitive. They called this a  conditional lethal albino  effect. Again, this is a report from the USDA wheat genetics literature but they made no mention of it being present in wheat. These reports lend credence to the supposition that albinism in winter wheat is a result of some und ocumented or at least poorly communicated genetic x environment interaction. The condition attracts a lot of attention during the early spring in eastern Oregon and Washington but doesn ’ t appear to be damaging the crop.