FOLIA BIOLOGICA ET GEOLOGICA 61/1, 25–36, LJUBLJANA 2020 BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE ŽLAHTNJENJE AJDE V PRETEKLOSTI, SEDANJOSTI IN PRIHODNOSTI Clayton G. CAMPBELL1 & Mio NAGANO1 http://dx.doi.org/10.3986/fbg0064 ABSTRACT Buckwheat Breeding. Past, Present and Future. Buckwheat crop improvement by breeding has been taking place over the past 100 years or more. During this time there has been improvements in many desirable agro- nomic characteristics which has resulted in higher yields in many of the breeding programs. Phenotypic modifications, such as dwarf, semi-dwarf and branching have been report- ed. There has also been an effort to increase flower number as this has been shown in cross pollinating buckwheat, to increase yields. Flower cluster modifications and their ef- fects on yield have also been studied. Increased reports on the discovery of buckwheat wild species have been reported from several programs with many interspecific crosses hav- ing taken place. Several of these crosses were performed with Fagopyrum esculentum in efforts to increase variability which can be used to increase yield potential as well as to obtain increased nutritional components. More recent ef- forts have focused on the development of self-pollinating buckwheat, both from introgression of genes from Fago- pyrum homotropicum as well as from mutations in cross pol- linating buckwheat. The main problem has been in breeding depression which has occurred in many of the reported at- tempts. However, high yielding homomorphic, self-pollinat- ing varieties have been developed and are now in commer- cial production. There is now emphasis being placed on many of the nutritional aspects of buckwheat flour as well as value added components. It is expected that this will in- crease over time. Key words: Buckwheat breeding, homomorphic, autoga- mous buckwheat. IZVLEČEK Žlahtnjenje ajde v preteklosti, sedanjosti in prihodnosti Žlahtnjenje ajde poteka že več kot 100 let. V tem času je bila dosežena izboljšava željenih agronomskih lastnosti, kar je pri mnogih programih žlahtnjenja omogočilo večje pridel- ke. Raziskovalci poročajo o fenotipskih modifikacijah, kot je pritlikava ali pol-pritlikava rast in razvejanje. Za povečanje pridelka so bile raziskane modifikacije socvetij. Število poročil o odkritjih divjih sorodnikov ajde in o mnogih med- vrstnih križanjih se je v zadnjem času povečalo. V mnoga od teh križanj je bila vključena navadna ajda (Fagopyrum escu- lentum), da bi povečali variabilnost, kar bi lahko omogočilo povečanje pridelka in izboljšanje prehranskih lastnosti. Novejša prizadevanja so se osredotočila na razvoj samoop- lodnosti pri ajdi, z vključitvijo genov vrste Fagopyrum homo- tropicum, kot tudi mutacij pri ajdi, ki se je opraševala navzkrižno. Pri tem je bila glavna težava preseči depresijo zaradi samooploditev, depresija se je pojavila pri večih poskusih samooploditve. Ne glede na to je uspelo dobiti vi- sokorodne homomorfne samooplodne sorte za ponudbo na trgu semen. Sedaj se prizadevanja usmerjajo k izboljšanju prehranske vrednosti ajde in pomembnih sestavin v ajdovi moki. Pričakovati je, da se bo pomen prehranske vrednosti ajde sčasoma še povečeval. Ključne besede: žlahtnjenje ajde, homomorfnost, samo- oplodna ajda 1 Canadian Buckwheat International, Morden, Manitoba, Canada R6M 1H1. E-mail: claytoncampbell@mymts.net CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 26 FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 INTRODUCTION Buckwheat (Fagopyrum esculentum) crop improve- ment has been ongoing for a very long time. It is a very nutritious crop and fits well into crop rotations. However, due to its heteromorphic sporophytic cross- ing system it has been a difficult species for plant breeders to make rapid progress. This has resulted in many other crops obtaining much higher yields and increased nutritional characteristics at a much faster rate that buckwheat. Therefore, there are many re- ports of countries and areas that have seen decreased production of buckwheat over the past century with marginal production now being the norm in many areas. Buckwheat crop improvement programs have pro- duced many new varieties with increases in yield or with other increased beneficial nutritional properties. However, when looked at from a commercial outlook there has been little change in yield from these efforts. Perhaps this is due to there being only a few buckwheat breeding programs world-wide focusing only on buck- wheat. Many of the present breeding efforts are com- bined with breeding on other crops and therefore have limited ability to make major improvements. Buck- wheat crop improvement must therefore become more coordinated in order that crop improvement objectives can be realized. PAST BUCKWHEAT BREEDING EFFORTS Due to Fagopyrum esculentum having a heteromorphic, sporophytic incompatibility system initial crop im- provement methods were achieved by selection. How- ever, this was maternal selection only as the pollen par- ent was unknown. Pollinations between individual plants or lines was severely restricted as all crossing parents and the resulting progeny had to have spatial or caged isolation from other buckwheat. Thus the breed- ing programs could only make limited improvements as compared to those made with rice, wheat or maize. Early studies have produced homomorphic self- fertile plants (Marshall 1969, Fesenko & Lokhato- va 1981) by probable mutations. However, in many cases these also had severe inbreeding depression from possible recessive mutations that could survive in cross-pollinating lines. There have been exceptions to this as the author found one line that was homomor- phic with short anthers and pistils and that had no in- breeding depression after several generations. There has been a lot of recent interest in attempt- ing interspecific crosses, especially after the finding and reporting of new buckwheat species (Ohnishi 1991, 1998a, 1998b, Chen 2016). The finding and iden- tification of these wild species of Fagopyrum has trig- gered, not only a lot of interest in studying the possi- ble interspecific crosses that can be possible, but has also resulted in the development of essential method- ology required in the making of the crosses, such as embryo rescue techniques or hot water emasculation. Although reports of successful crosses that have been made (Wang & Campbell 1998, Chen 2016) have cre- ated a great deal of interest in this area, many of the interspecific hybrids have been found to be sterile. The major exception to this has been the cross of Fago- pyrum esculentum by Fagopyrum homotropicum (Cam- pbell 1995). This cross has paved the way to successful introgression of the self-compatible character into common buckwheat. Nutritional aspects of buckwheat has also received interest in the past. Increasing the rutin content has been the focus of some breeding programs and buck- wheat germplasm collections have been screened and high rutin accessions have been identified. Certainly buckwheat has long been viewed as having other desir- able nutraceutical properties and these have also re- ceived attention. PRESENT BUCKWHEAT BREEDING EFFORTS Buckwheat breeding programs at the present time are almost all focused on cross-pollinating common buckwheat. Although Tartary buckwheat has re- ceived limited interest, especially in easy dehulling types, there has not been a concerted effort on this crop. Much of the common buckwheat in the large area of India, China, Nepal and Bhutan is mainly grown in high, arid regions in the mountains. It is grown as a subsistence crop and as such is an essen- tial part of the diet for these people, however, these CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 27FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 areas do not appear to get the notice or support re- quired to better support their needs. Most of the buckwheat grown are local land races that have re- ceived selection from the growers although there are some varieties available that have been developed by public institutions. Buckwheat germplasm efforts have received atten- tion in several countries around the world. Many of these have been characterized and evaluated for quali- tative and quantitative traits so that they are now avail- able for utilization in buckwheat improvement pro- grams. However, there is an increasing loss of genetic variability in many areas and this has become a critical issue (Rana, Singh & Yadav 2016). Efforts in yield improvement in cross-pollinating common buckwheat have been mainly centered on flower number, cluster number, branching habit, plant habit, leaf size and shape, days to maturity and per- centage seed set. As the percentage seed set in buck- wheat is very low, usually in the range of 11 to 12 per- cent of flowers produced, this has resulted in plants with more flowers in order to increase yield. The high abortion rate has been the major obstacle of obtaining higher yielding cultivars. FUTURE BUCKWHEAT BREEDING EFFORTS Buckwheat breeding efforts, despite the consumption and varied uses of this crop, sadly lacks a major, coor- dinated effort. It appears that the most interest in past buckwheat breeding programs has been on the com- mercial aspects of the crop. Although this is a very valid reason for these efforts, the needs of the poor growers that utilize this essential crop for their subsist- ence has been sadly neglected. Most of the agronomic studies have been conducted to increase yields or nu- tritional aspects of the crop in high input agricultural management systems and there is a dearth of informa- tion on production aspects of this crop under subsist- ence farming practices which growers in these areas. As common buckwheat has a very high abortion rate, of almost 88% of flowers produced, this is one of the major concerns which must be addressed in order for higher yielding cultivars to be developed, which can compete better with other crops for grower acceptance. The production of such a high percentage of flowers that do not contribute to yield but require a very large input from the plants will require coordinated efforts to overcome. Unfortunately, the finding of plants/lines that have a much lower flower number but still achieve high yields is extremely difficult. But as a doubling of yield should only require about 25% of the flowers now being produced then the inputs the plant is now putting into the 75% of the flowers which do not contribute to yield could be diverted into seed production. As there is a great deal of variability in cluster shape and number, as well as in flower number, that has been found in self- pollinating buckwheat perhaps this is where the most future efforts should be expended (Figs. 1 – 17). REFERENCES Campbell, C., 1995. Inter-specific hybridization in the genus Fagopyrum. Proceedings of the 6th International Symposium on Buckwheat, 255-263. Chen, Q., 2016. Recent progress on interspecific crossbreeding of genus Fagopyrum Mill. Proceedings of the 13th International Symposium on Buckwheat, 285-298. Fesenko, N., Lokhatova, V., 1981. Self-compatibility of Zamyatkin’s homostylous long-styled buckwheat form. Doklady Vsesoyuznoi Ordena Lenina Akademii Sel’skokhozyaistvennykh Nauk Imeni VI Lenina, 16-17. Marshall, H., 1969. Isolation of self-fertile homomorphic forms in buckwheat Fagopyrum saggitatum Gilib. Crop Science 9, 651-653 Ohnishi, O., 1991. Discovery of the wild ancestor of common buckwheat. Fagopyrum 11, 5-10. Ohnishi, O., 1998a. Search for the wild ancestor of buckwheat III. The wild ancestor of cultivated common buck- wheat, and of tartary buckwheat. Economic Botany 52, 123-133. Ohnishi, O., 1998b. Search for the wild ancestor of buckwheat. 1. Description of new Fagopyrum (Polygonacea) species and their distribution in China and Himalayan hills. Fagopyrum 15, 18-28. Rana, J.C., Singh, M., and Yadav, R., 2016. Germplasm resources in India. Proceedings of the 13th International Symposium on Buckwheat, 49-63. CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 28 FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Wang, Y., Campbell, C. 1998. Interspecific hybridization in buckwheat among Fagopyrum esculentum, F. homo- tropicum, and F. tataricum. p. I: 1-13, Proceedings of the 7th Int. Symposium on Buckwheat, 12-14. Fig. 1: Field of self pollinating buckwheat Slika 1: Polje s samooplodno ajdo Fig. 2: Leaf sizes Slika 2: Velikosti listov CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 29FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 3: Plant habit of Kiku types Slika 3: Kiku oblika rastlin Fig. 4: Kiku branching habit Slika 4: Razvejanje pri rastlinah Kiku CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 30 FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 5: Kiku has very short internodes at first Slika 5: Na začetku rasti so internodiji zelo kratki Fig. 6: Early Kiku growth Slika 6: Začetek rasti pri Kiku CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 31FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 7: Early ground cover by Kiku Slika 7: Rastline Kiku hitro pokrijejo tla Fig. 8: Plant with early ‘weed control’ leaves Slika 8: Rastlina z obliko listov, ki zgodaj zasenčijo rast plevelov CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 32 FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 9: Enhanced green testa types Slika 9: Različne stopnje zelenega obarvanja teste Fig. 10: Flower cluster types that have been found in common buckwheat Slika 10: Različne oblike socvetij ki smo jih ugotovili pri ajdi CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 33FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 11: Enhanced flower clusters Slika 11: Povečano število socvetij Fig. 12: Enhanced flower cluster plants Slika 12: Rastline z obogatenimi socvetji CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 34 FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 13: Differing auxillary flower cluster types Slika 13: Različni tipi stranskih socvetij Fig. 14: Determinant flower clusters Slika 14: Socvetja ajde s končno rastjo CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 35FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 15: Ball cluster Slika 15: Kroglasto socvetje Fig. 16: Plant with ballclusters Slika 16: Rastlina s kroglastimi socvetji CLAYTON G. CAMPBELL & MIO NAGANO: BUCKWHEAT BREEDING. PAST, PRESENT AND FUTURE 36 FOLIA BIOLOGICA ET GEOLOGICA 61/1 – 2020 Fig. 17: Red pericarp Slika 17: Rastlina z rdečim perikarpom