تاثیر فواصل مختلف آبیاری بر برخی خصوصیات مورفوفیزیولوژیک اکوتیپ‌های مختلف گوار (Cyamopsis Tetragonaloba)

آزمایشی به صورت کرت‌های خردشده در قالب طرح بلوک کامل تصادفی، در سال های 97-1396 در مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی شهرستان ایرانشهر اجرا شد. در این آزمایش سه سطح آبیاری با فواصل 5، 7 و 9روزه به‌عنوان فاکتور اصلی و اکوتیپ‌های مختلف گوار (سرباز، سراوان، ایرانشهر،rgc1033، هندی،گرمبیت) به‌عنوان فاکتور فرعی در نظر گرفته شد. کاشت بذر گوار در اسفندماه انجام شد و پس از استقرار گیاه در مرحله پنج‌برگی آبیاری با دورهای مختلف آغاز و تا مرحله برداشت بذرها ادامه یافت. با افزایش فاصله آبیاری ارتفاع گیاه اکوتیپ سرباز و سراوان به ‌‍طور معنی داری کاهش یافت، اما تاثیری بر سایر اکوتیپ‌ها نداشت. طول ریشه اکوتیپ هندی با افزایش فاصله آبیاری به طور معنی‌داری کاهش یافت، درحالی‌که در اکوتیپ اصلاح‌شده rgc1033 و اکوتیپ‌های ایرانشهر و سرباز با افزایش فواصل آبیاری طول ریشه افزایش یافت. افزایش دور آبیاری باعث کاهش معنی دار حداکثر کارآیی کوانتومی فتوسیستم (fv/fm) ii در اکوتیپ‌های سرباز، گرمبیت و ایرانشهر شد. با افزایش دور آبیاری شاخص برداشت کاهش یافت، به طوری‌که بیشترین میانگین شاخص برداشت در دور آبیاری پنج روز به‌دست آمد. بیشترین میانگین عملکرد بیولوژیک در دور آبیاری هفت روز و اکوتیپ سراوان مشاهده شد. با توجه به صفات مختلف بررسی‌شده، اکوتیپ اصلاحی rgc1033 و اکوتیپ سراوان در بیشتر صفات مورد بررسی دارای بیشترین میانگین بودند. با توجه به نتایج به دست آمده دور آبیاری هفت روز مناسب‌ترین دور آبیاری جهت کشت گوار در مناطق جنوبی کشور پیشنهاد می‌شود.

Effect of different irrigation intervals on some morphophysiological characteristics of different genotypes of Guar (Cyamopsis tetragonoloba)

IntroductionGuar (cluster bean) Cyamopsis Tetragonaloba is one year plant belongs to the leguminous family. Guar has high nutritional value for humans. Global demand for guar has increased dramatically in recent years, which has led to the introduction of the plant in several countries. Water stress is the most important factor limiting planting and reducing food crops, especially in arid and semiarid regions of the world. Therefore, identification of resistant plants and mechanisms that lead to optimal water use and high crop yields are critical. Given the limited water resources in the country, the evaluation of guar stands under drought stress is of particular importance. Materials and MethodsThe experiment was carried out at the Research Farm of Iranshahr Agricultural and Natural Resources Faculty in 201718. The experiment was conducted as a splitplot in a randomized complete block design with three replications. Three levels of irrigation interval (7, 5, and 9 days) and six guar stands (Sarbaz, Saravan, Iranshahr, RGC1033, Indian, and Grembit) were considered as main and subfactors, respectively. After planting in the 5leaf stage, the stress operation began and continued until the seeds were harvested. At the end of the growing season, samples were transferred to the laboratory and shoot length and root length, fresh and dry weight of shoot, fresh and dry root weight, number of branches, 100 seed weight were measured. Leaf chlorophyll index was measured using Spad 502 Minolta chlorophyll meter. The chlorophyll fluorescence was measured using a HandyPEA portable fluorometer (Hansatech Instruments). Finally, statistical analysis was performed using SAS software and mean comparisons were made using the LSD test at 5% probability level. Results and DiscussionIncreasing irrigation intervals significantly decreased plant height in Sarbaz and Saravan. The results showed that at 9day irrigation period, the highest plant height (77.5 cm) was related to RGC1033 which did not show any significant difference with Saravan. The lowest plant height (42.03cm) was related to Sarbaz ecotype. Results showed that the 9day irrigation interval increased root length in RGC1033, Iranshahr and Sarbaz and significantly reduced root length in Indian ecotype. The results showed that in 9day irrigation period the number of branches in Iranshahr and Grambit decreased but increased in Saravan and RGC1033 genotypes. While the irrigation interval had no effect on Sarbaz ecotype. Most of the branches were 5.7 in RGC1033 ecotype. The Indian ecotype lacked a branch at all irrigation intervals. At 9day irrigation period, Saravan and Iranshahr had the highest leaf dry weight. In Iranshahr and RGC1033 genotype, fresh and dry weight increased. Increasing irrigation interval resulted in a significant decrease in the dry weight of Indian root. The irrigation period had no significant effect on Saravan and Grambit ecotypes. Increasing irrigation intervals did not have a significant effect on the Sarbaz, Grambit, and Indians. With increasing irrigation intervals in RGC1033, Saravan and Iranshahr dry weights increased. The simple effect of ecotype type on seed weight showed that Saravan, Indian, and Iranshahr had the highest seed weight, respectively. Whereas, the SG, RGC1033, and Grambit had the lowest seed weight without any significant differences together. Saravan ecotype at all irrigation levels showed more biological function than other ecotypes. Results showed that the harvest index decreased with increasing irrigation intervals. In the 5day irrigation treatment, the Grambit and Saravan ecotypes had the highest and the lowest harvest index, respectively. The 9day irrigation period significantly reduced Fv/Fm in Sarbaz, Grambit, and Iranshahr. RGC1033 and Indian populations had the highest Fv/Fm in leaves and Saravan and Iranshahr had the lowest Fv/Fm in leaves at 7 days irrigation period, respectively. The number of pods per plant, number of lateral branches, 100 seed weight and plant height have a direct and positive effect on guar yield. Under drought stress, plant height and leaf number decrease, resulting in lower shoot dry weight. Some researchers showed that decreasing plant height under water stress is associated with loss of protoplasmic water, resulting in reduced cell division and development. The harvest index decreased with decreasing number of pods, thereby reducing economic yield. Differences between susceptible and resistant ecotypes appear in highstress conditions and high Fv/Fm ratio ecotypes have higher photosynthetic efficiency under severe stress conditions. Chlorophyll fluorescence is considered as a criterion for assessing the integrity of the thylakoid membrane in the relative efficiency of electron transfer from Photosystem II to Photosystem I. ConclusionMean root length, the number of branches, fresh and dry weight of RGC1033 were not affected by a 9day irrigation interval. In the 9day irrigation period, the highest mean dry weight of leaf, main stem weight and seed weight were related to Saravan ecotype. The highest biological yield was observed in the irrigation period of 7day and Saravan ecotype. In general, the results showed that irrigation had different effects on different guar populations. RGC1033 and Saravan ecotypes showed the lowest percentage of stressaffected variations.