Sugar beet environmental stresses (drought and salinity) in Iran: Physiology, breeding, agronomy and biotechnology

Environmental stresses, especially drought and salinity, are among the major factors limiting the production of crops including sugar beet in arid and semi-arid regions of the world. With an annual precipitation of 240 mm, Iran is calssified as a dry region of the world. On the other hand, over 17% of country'a area is occupied by saline soil.Thus, for the production of crops to be economic in these regions, it is necessary to condider breeding and agronomic aspects. Various projects are needed to study all these aspects. Following cultural practices such as alteration of sowing pattern, proper nutrition and crop protection against diseases and pests can help increasing crop productivity in stressed environments. One of the most important objectives of sugar beet research is to develop drought or salt tolerant cltivars that can produce reasonable yield in farmers fields. As almost all the present sugar beet varieties are hybrid, tolerance in the both male and female parents should be taken into account. The ultimate goal of the current research plan is to develop the improved monogerm and multigerm sugar beet varieties with good gronomic and technological characters as well as high yield per unit area. This research plant consists of two sub-plans, drought and salinity, with 19 and 15 projects each, respectively. In the both sub-plans, breeding and agronomic aspects, including the breeding of male and female parents for developing drought 78 tolerant varieties have been taken into consideration. However, due to a long procedure for development of tolerant female parents, main emphasis has been devoted to the development of male parents. The outcome of the current research plan is development and production of desirable pollinators that produced some promising hybrids. Study of morphological, physiological and yield-based statistical indices indicated that drought tolerance of germplasm resources could be evaluated by using canopy temperature depression, quantum yield efficiency (Fv/Fm), leaf number, specific leaf weight and drought tolerance index (STI). Among the drought tolerant materials indentified are the populations 7219-P.69, 12681-P.20, 12681-P.33, C3.3, 428 and Otype NB5. Also, the S1 pollinator lines 113, 116, 142, 143, 158 and 175 selected from the original diploid pollinator population BP Mashad were found to be drought tolerant. Comparison of multigerm hybrids in two locations, Karaj and Mashad, showed that the hybrids (CMSI13*A37.1) *BP.Karaj and (CMSI13 * A37.1) * BP.Mashad were more drought tolerant than the others. In another project which was carried out based on four initial diploid populations (SBSI DR _ I ¡ SBSI DR _ II ¡ BP KARAJ and 436 BIGERM), the highest root yield across two years and two locations belonged to the monogerm hybrids (436*231)*SBSI-DRIHSF- 14.P.35 and (436*231)*SBSI-DRI-HSF-14.P.7. These two hybrids were superior to the foreign chech varieties as well as othe hybrids, so they can be introduced as drought tolerant hybrids for commercial cultivation. 7233- æ 30 - In one of the salinity projects, the progenies 7233- P.29-19 ¡ 7233- P.29 P.29- 28 which were selected from the diploid population 7233- P.29 when crossed with the male sterile line MSC2 had higher root and white sugar yields than the check variety. The diploid populations 9669-P.24¡ 9597-P3¡ BP KARAJ¡ 9671-P.10 and BP MASHAD were also found to be salt tolerant. In another salinity project, S1 lines developed from A1 and C2 Otype lines were used to produces single cross hybrids. These hybrids were crossed with the salt tolerant population 7233-P.29. The 21 resultant hybrids were evaluated for salt tolerance. In a separate project, the multigerm hybrid MSC2×9529-II and the monogerm hybrid (231× 261) × 7233-I- p.21 produced a higher white sugar yield than the other hybrids under salinity condition. Also, the tetraploid populations 13030 and C3.3 were identified as salt tolerant pollinators which were used to develop thriploid hybrids. Among these hybrids, the monogerm thriploid hybrids (261×231) × C3.3 and (261×231) × 13030 and the multigerm thriploid hybrids MSC2× C3.3 and MSC2×13030 were superior to the salt tolerant check varieties and introduced as promising hybrids for final evaluations. Furthermore, the experiments conducted under salt stress and non-stress conditions in Isfahan and Miandoab locations showed that for Isfahan, the hybrids 29059 and 29061 and for Miandoab, the hybrids 29064 and 29071 could be recommended. Results of sugar beet transplanting method in salt-affected areas indicated that this method has a higher effect on yield than quality. Also, early sowing and two-row planting are recommended for salt-affected areas due to facilited irrigation and lack of salt accumulation at the seed emergence zone.