Person: Mann, C.E.
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Mann, C.E.
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- Boron deficiency in wheat(CIMMYT, 1992) Mann, C.E.; Rerkasem, B.Boron deficiency in soils has been reported to affect more and more crops, especially so in the warmer environments. Two reasons come to mind: Either the problem has not been recognized in the past and the symptoms have not been attributed to other causes, or Intensification of cropping over the last few decades has accelerated depletion of existing soil boron. Probably both of these playa role. In a timely manner, the Australian Centre for International Agricultural Research (ACIAR) has supported research in boron deficiency of grain legumes at Chiang Mai University (CMU) in Thailand. More recently, the Australian International Development Assistance Bureau (AIDAB) has provided funds to the regional office ofthe International Maize and Wheat Improvement Center (CIMMYT) in Southeast Asia to cooperate with CMU as an expert institution and national research institutions in South and Southeast Asia to gain some more knowledge about the same problem in wheat. Part of this project was a small boron workshop conducted at Chiang Mai University, Feb. 17-19, 1992, the proceedings of which make up this Wheat Special Report. The various papers report a wide range of findings and knowledge currently available in South and Southeast Asia. Some results of the AIDAB-funded research are also included. Generally, micronutrient deficiency research requires special care as compared to toxicity work or macronutrient experimentation (Loneragan, page 1) because contamination occurs easily during the experimental process and tiny amounts can blur results. Problems also arise frequently due to the masking effect of other nutrient deficiencies in poor soils. The major symptom of boron deficiency in wheat is grain set failure. Wheat growing in low boron soils may develop malformed anthers and pollen grain; the external boron supply may also limit the germination of healthy pollen (Cheng and Rerkasem, page 5). Prediction of grain set failure from boron analysis of wheat tissues is complicated (Rerkasem and Lordkaew, page 9) because 1) boron is immobile inside the plant, and 2) grain set fails if boron availability is interrupted during a few crucial days at pollen development or fertilization. On the other hand, chemical analysis ofsoil or plant tissue boron does not require highly sophisticated equipment and can be done in many laborato~ies (Netsangtip and Lordkaew, page 15). Once boron deficiency is established through chemical analysis as the most probable factor causing sterility in a given environment, then other more simple methods can be employed for surveys or varietal screening. These methods could include boron probe nurseries (Rerkasem, page 21), measurements of anthers and pollen (Cheng et aI., page 32) or grain set counting as the simplest and most rapid method (Appendix 2, page 126). How widespread is the problem? Various soils are prone to boron deficiency (KhatriChhetri and Ghimire, page 34) and reports are available from many countries worldwide (see bibliography in Appendix 1, page 113). But despite numerous anecdotal observations of severe sterility problems in different years by researchers from national programs, nobody reports yield loss estimates on a national or even provincial level. This does not mean losses are minimal, but given the year to year changes of water status, which in turn controls boron availability, varietal differences, macronutrient fertilizer contamination with boron, and temperature at flowering plus the difficulty of determining boron as the cause of sterility make loss estimates of a sizeable area a formidable task. Most probably, minor sterility often goes unrecognized. Ifit is severe, it can also be attributed to drought, cold, or waterlogging (Subedi, page 57). It is unclear whether waterlogging alone can cause sterility (Misra et aI., page 65) or whether it is only an indirect factor reducing the availability and/or uptake of boron. Superimposed boron fertilizer experiments (Yang, page 72) may show one way to obtain better yield loss estimates, but due to the above mentioned interactions, fertilizer experiments are not always conclusive (Subedi). Due to all these problems, there is currently a lack of awareness and diagnosis as well as inadequate research for solutions. Varietal differences are reported by many authors from various soils based on experiments in farmers' fields (Yang), experiment stations (Tandon and Naqvi, page 76; Misra et aI.; and Subedi) or under controlled conditions in sand culture (Jamjod et aI., page 79; numerous additional references can be found in Appendix 1). First estimates of inheritance and heritability (Jamjod et aI., page 86) as well as mode of gene action (Jamjod et aI., page 83) are available. Nevertheless genetic knowledge is still far from what is known about boron toxicity (Paull et aI., page 90) although some inferences can be made. In the same way, physiological research of boron toxicity in wheat adds to the present knowledge of physiological processes in boron-deficient wheat plants (Nable, page 98). Much remains to be researched for a better understanding of the problems as well as for the most practical solutions. The workshop participants listed areas in which they would want to continue research on their own or in cooperation with the current project and beyond (See minutes of final discussion, page 110).
Publication - Results of the 1st International Heat Stress Genotype Experiment(CIMMYT, 1992) Reynolds, M.P.; Acevedo, E.; Ageeb, O.A.A.; Ahmed, S.; Balota, M.; Carvalho, L.J.B.; Fischer, R.A.; Ghanem, E.; Hanchinal, R.R.; Mann, C.E.; Okuyama, L.; Olugbemi, L.B.; Ortiz-Ferrara, G.; Razzaque, M.A.; Tanndon, J.P.Fischer (1989) summarized the detrimental effects of high temperature on wheat growth as follows: Yield reduction can occur at temperatures above a mean as low as 150C, with the spike and grain growth phases being especially sensitive; and With very hot conditions during stand establishment, lack of full ground cover will further contribute to yield loss. Mechanistically, it seems that high temperatures affect a number of physiological processes, apart from rate of development (see Discussion), although causal links between these processes and yield loss in the field environment have not previously been well established. The interaction between these mechanisms and genotype form the basis of our investigations. Probably the greatest challenge in understanding the physiological problems associated with high temperature stress is to encompass the diversity of hot environments that exist. These can be put into four broad categories: Hot dry, Hot humid, Very hot dry, and Very hot humid. Hot and very hot are climates where the mean temperature for the coolest month of the cycle is greater than 17.5 and 22.50 C, respectively. Dry and humid are climates where the mean vapor pressure deficits are above and below 10 mb, respectively for the crop cycle (Fischer and Byerlee 1991). Since the experiments described in this special report have been conducted on a multilocational basis as a collaboration between CIMMYT and national programs in warm wheat growing environments (Table 1), we anticipate that our results will be representative of the range of warm climates that exist. The International Heat Stress Genotype Experiment (IHSGE) is designed to look closely at a small number of traits which, in preliminary studies at CIMMYT and in consultation with CIMMYT outreach staff and other researchers in hot environments, seem to have potential value as predictors of yield at high temperatures.
Publication - Wheat and wheat development in Bhutan(CIMMYT, [1988?]) Mann, C.E.; Hobbs, P.R.This report summarizes the work of two CIMMYT regional scientists who visited Bhutan Oct 18-Nov. 1 1988 to prepare a paper on wheat and wheat development in Bhutan at the request of the government. Wheat is the third most important cereal crop in Bhutan, but is not the preferred staple. As such, it has received little research attention and farmers grow it as a less important subsistence crop. Yields are low compared to other South Asian countries. The government of Bhutan wishes to intensify wheat production to help achieve self-sufficiency in food grains and increase small farmer incomes. Figures for the acreage and production of wheat for the whole of Bhutan are only available for 1984. In that year, Bhutan produced 11,880 metric tons (MT) of acres (3,735 ha). No data are available after 1984 to compare production in 1988 or to predict trends. However, it is believed that the targets set for the Fifth 5- Year Plan were not met. Reseasons for this shortfall are not known. Bhutan imported 5,519 MT of wheat from India from April 1, 1987 to june 30, 1988. Most of this wheat was distributed as flour to the urban areas of western Bhutan and major development projects in the West. Wheat is mainly utilized in Bhutan as subsistence food and prepared to resemble rice. Some is used as chapatis mainly by the foreign workers from India and Nepal. There is a growing demand for bread products in the urban centers. An undetermined amount of wheat and barley is used for production of alcohol and a certain amount is cut as green fodder for animals. Wheat ir grown in all zones of Bhutan. Mostly, it follows paddy rice or maize but no data are available on percentages. Wheat is irrigated after paddy and rainfed after maize and is always grown as winter crop. The spring wheat variety Sonalika is predominant up to 2500 masl; local winter wheats are grown at higher elevations. Production methods reflect the low importance and subsistence nature of this crop. Very little inorganic fertilizers are used and most nutrients come from applied data are available on the production practices for this crop. The Centre for Agricultural Research and Development (CARD) at Wangdiphodrang initiated research on wheat in 1982. Work on selection of suitable materials to replace Sonalika has received most attention. Little work has been done on agronomy issues, although an FAO fertilizer project has several years of data on wheat responses to N-P-K in different parts of the country. Stripe rust is the major disease problem and Sonalika is susceptible. The economics of wheat production are negative in terms of net returns and returns to labor in the Wangdi-Punakha Valley where labor costs are very high. In three other promotional areas where labor is cheaper, net returns and returns to labor are good assuming the government will procure the excess production at 3 Ngultrums (US$ 0.21)/kg. With the policy of the government to promote wheat, research must concentrate on technology that reduces the cost of production and use of labor, while at the same time increases yield. Until costs of production can be reduced, wheat production in Bhutan will not be competitive with imports from India. Crop management research offers many opportunities for increasing productivity. Improved crop establishment, earlier planting, zero tillage, mechanization, use of fertilizer and irrigation and water management are discussed in technical terms to meet this goal. Fertilizer issues especially efficiency, use of organic manures, green manuring, and the problems of sustainability and yield decline are urgent issues for research. This latter problem must receive attention to prevent the productivity of the land from declining with time.
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